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• Help with visual programming??

  - by tjk0102

  i'm making a program that i need help with i'm trying to duplicate impero's policy lock screen i need help i'm trying to have my program search to see if a file is there. the concept is if the file exists it will launch it,but i'm having troubles would i use background worker do search for it and if so how would i make it search for it? if you can help that will be great

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• re: adding more threads to forkjoinpool

  - by paintcan

  Word up y'all I recently successfully experimented with Scala futures, got future { my shiznit } all over da place. I'm pleased as punch w/ the gains I'm seeing from the parallelism and whatnot, but I'm only seeing 4 worker threads. Wanna see some more. I've been looking all over for how I can crank up the number of threads to 11, but no luck. Help me out doods

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• Have you actually convinced anybody to Scala?

  - by Lukasz Lew

  I had limited success myself. I was able to hype a few persons about Scala. But in fact none of them made a meaningful effort to try to switch (usually from Java). I would like to read both success and failure stories here. Both long tries and short ones. My goal is to find ways of presenting Scala to another person, friend, co-worker (not an audience) that will make them want to use this great language.

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• Tools for Debugging ThreadPool Issues in Visual Studio 2010.

  - by ProfK

  I have never spent much time debugging multithreaded .NET apps (or others), and have quite a simple one to solve very quickly. Ideally I would imagined and would lurve to be able to intercept thread creation and use by worker objects, so that nothing unexpected happens while I'm on a breakpoint in my thread. Is that realistic? What else is there in VS 2010?

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• How do you go about setting up monitoring for a non-web frontend process?

  - by ming yeow

  I have a worker process that is running in a server with no web frontend. what is the best way to set up monitoring fot it? It recently died for 3 days, and i did not know about it

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• Application crashing while closing

  - by subbu

  Hi All, I have a c# exe which uses some c++ dlls . I use DllImport in my c# exe to use my c++ dlls. Now my problem is when I close my application my application crashes. I am not sure why Its crashing. My c++ dll is multithreaded and my c# exe has Background worker

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• SwingWorker exceptions lost even when using wrapper classes

  - by Ti Strga

  I've been struggling with the usability problem of SwingWorker eating any exceptions thrown in the background task, for example, described on this SO thread. That thread gives a nice description of the problem, but doesn't discuss recovering the original exception. The applet I've been handed needs to propagate the exception upwards. But I haven't been able to even catch it. I'm using the SimpleSwingWorker wrapper class from this blog entry specifically to try and address this issue. It's a fairly small class but I'll repost it at the end here just for reference. The calling code looks broadly like try { // lots of code here to prepare data, finishing with SpecialDataHelper helper = new SpecialDataHelper(...stuff...); helper.execute(); } catch (Throwable e) { // used "Throwable" here in desperation to try and get // anything at all to match, including unchecked exceptions // // no luck, this code is never ever used :-( } The wrappers: class SpecialDataHelper extends SimpleSwingWorker { public SpecialDataHelper (SpecialData sd) { this.stuff = etc etc etc; } public Void doInBackground() throws Exception { OurCodeThatThrowsACheckedException(this.stuff); return null; } protected void done() { // called only when successful // never reached if there's an error } } The feature of SimpleSwingWorker is that the actual SwingWorker's done()/get() methods are automatically called. This, in theory, rethrows any exceptions that happened in the background. In practice, nothing is ever caught, and I don't even know why. The SimpleSwingWorker class, for reference, and with nothing elided for brevity: import java.util.concurrent.ExecutionException; import javax.swing.SwingWorker; /** * A drop-in replacement for SwingWorker<Void,Void> but will not silently * swallow exceptions during background execution. * * Taken from http://jonathangiles.net/blog/?p=341 with thanks. */ public abstract class SimpleSwingWorker { private final SwingWorker<Void,Void> worker = new SwingWorker<Void,Void>() { @Override protected Void doInBackground() throws Exception { SimpleSwingWorker.this.doInBackground(); return null; } @Override protected void done() { // Exceptions are lost unless get() is called on the // originating thread. We do so here. try { get(); } catch (final InterruptedException ex) { throw new RuntimeException(ex); } catch (final ExecutionException ex) { throw new RuntimeException(ex.getCause()); } SimpleSwingWorker.this.done(); } }; public SimpleSwingWorker() {} protected abstract Void doInBackground() throws Exception; protected abstract void done(); public void execute() { worker.execute(); } }

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• How to adjust SQL LIKE function?

  - by slave016

  I want to make this kind of query: create procedure something @name varchar(13) as begin select * from WORKER where NAME LIKE "%@name%" end For input @name=ho, I want output every row that contains NAME wich sounds "ho", for example HOuse, soHO, broHOw...

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• an alternative to progressbar?

  - by ammu

  could anybody knows any alternatives to progressbar? Inmy project im using progressbar..I would like to change it to something like a rotating gif image which indicates the processing or someother labels which prevents the user from interacting to the program.I tried to implement the gif image by using background worker but its hanging may be coz of huge file transfer process.. So im searching for someother alternative like a label which will disable the content and prevent the user to interact with the program. Could anybody help me on this?

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• Option To AutoFormat Query Syntax in SSMS 2005 or 2008?

  - by dragon77

  In TOAD (for SQL or Oracle), there is a simple AUTOFORMAT button that will nicely format your query - I couldn't find that option in SSMS 2005, but was advised by a co-worker that it was available in SSMS 2008. I am unable to locate the option there either. This is VERY helpful when pasting a query from another source. Thanks for any assistance.

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• Why should I pass Boolean as a parameter instead of "boolean"?

  - by ferrari fan

  Hi, A co-worker asked me to change a signature from using a primitive "boolean" to using a classed "Boolean". He didn't offer a very good explanation why? Have any of you heard of this and can any of you explain why it matters or doesn't matter? Edit: He mentioned that it was good practice for public methods.

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• Simple tool/steps for obfuscating/scrubbing production data

  - by Krishna Kumar

  I am involved in a project where I need to provide subset of our production data (for a date range) to one of my co-workers for trouble shooting.I would like to insert a scrubbed subset of the production data into a new database table that my co-worker can access. Please suggest best approach to achieve this.

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• C# lines of Code

  - by matt

  What does this do exactly? var counts = new Dictionary<string, int>(); for (int i = 0; i < 10; i++) counts[string.Format("STA Thread Queue Worker Thread No. {0}", i + 1)] = 0; Thanks

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• Is it thread safe to read a form controls value (but not change it) without using Invoke/BeginInvoke from another thread

  - by goku_da_master

  I know you can read a gui control from a worker thread without using Invoke/BeginInvoke because my app is doing it now. The cross thread exception error is not being thrown and my System.Timers.Timer thread is able to read gui control values just fine (unlike this guy: can a worker thread read a control in the GUI?) Question 1: Given the cardinal rule of threads, should I be using Invoke/BeginInvoke to read form control values? And does this make it more thread-safe? The background to this question stems from a problem my app is having. It seems to randomly corrupt form controls another thread is referencing. (see question 2) Question 2: I have a second thread that needs to update form control values so I Invoke/BeginInvoke to update those values. Well this same thread needs a reference to those controls so it can update them. It holds a list of these controls (say DataGridViewRow objects). Sometimes (not always), the DataGridViewRow reference gets "corrupt". What I mean by corrupt, is the reference is still valid, but some of the DataGridViewRow properties are null (ex: row.Cells). Is this caused by question 1 or can you give me any tips on why this might be happening? Here's some code (the last line has the problem): public partial class MyForm : Form { void Timer_Elapsed(object sender) { // we're on a new thread (this function gets called every few seconds) UpdateUiHelper updateUiHelper = new UpdateUiHelper(this); foreach (DataGridViewRow row in dataGridView1.Rows) { object[] values = GetValuesFromDb(); updateUiHelper.UpdateRowValues(row, values[0]); } // .. do other work here updateUiHelper.UpdateUi(); } } public class UpdateUiHelper { private readonly Form _form; private Dictionary<DataGridViewRow, object> _rows; private delegate void RowDelegate(DataGridViewRow row); private readonly object _lockObject = new object(); public UpdateUiHelper(Form form) { _form = form; _rows = new Dictionary<DataGridViewRow, object>(); } public void UpdateRowValues(DataGridViewRow row, object value) { if (_rows.ContainsKey(row)) _rows[row] = value; else { lock (_lockObject) { _rows.Add(row, value); } } } public void UpdateUi() { foreach (DataGridViewRow row in _rows.Keys) { SetRowValueThreadSafe(row); } } private void SetRowValueThreadSafe(DataGridViewRow row) { if (_form.InvokeRequired) { _form.Invoke(new RowDelegate(SetRowValueThreadSafe), new object[] { row }); return; } // now we're on the UI thread object newValue = _rows[row]; row.Cells[0].Value = newValue; // randomly errors here with NullReferenceException, but row is never null! }

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• django, mod_wsgi, MySQL High CPU - Problems

  - by Red Rover

  I am having a problem with an OSQA site. It is Django/Apache/mod_wsgi configured site. Every hour, the CPU spikes to 164% (Average) for task HTTPD. After 10 minutes, it frees back up. I have reviewed the logs, cron tables, made many config changes, but cannot track this problem down. Can someone please look at the information below and let me know if it is a configuration problem, or if anyone else has experienced this issue. Running TOP shows HTTPD using 165% of CPU VMware performance monitor also displays spikes. This happens every hour for 10 minutes. I have the following information from server status Server Version: Apache/2.2.15 (Unix) DAV/2 mod_wsgi/3.2 Python/2.6.6 Server Built: Feb 7 2012 09:50:15 Current Time: Sunday, 10-Jun-2012 21:44:29 EDT Restart Time: Sunday, 10-Jun-2012 19:44:51 EDT Parent Server Generation: 0 Server uptime: 1 hour 59 minutes 37 seconds Total accesses: 1088 - Total Traffic: 11.5 MB CPU Usage: u80.26 s243.8 cu0 cs0 - 4.52% CPU load .152 requests/sec - 1682 B/second - 10.8 kB/request 4 requests currently being processed, 11 idle workers ....._..........__......W....................................... ...................................C._..._....._L__._L_._....... ...................... Scoreboard Key: "_" Waiting for Connection, "S" Starting up, "R" Reading Request, "W" Sending Reply, "K" Keepalive (read), "D" DNS Lookup, "C" Closing connection, "L" Logging, "G" Gracefully finishing, "I" Idle cleanup of worker, "." Open slot with no current process Srv PID Acc M CPU SS Req Conn Child Slot Client VHost Request 0-0 - 0/0/34 . 0.42 327 17 0.0 0.00 0.67 127.0.0.1 osqa.informs.org OPTIONS * HTTP/1.0 1-0 - 0/0/22 . 0.31 339 32 0.0 0.00 0.26 127.0.0.1 osqa.informs.org OPTIONS * HTTP/1.0 2-0 - 0/0/22 . 0.65 358 10 0.0 0.00 0.31 127.0.0.1 osqa.informs.org OPTIONS * HTTP/1.0 3-0 - 0/0/31 . 1.03 378 31 0.0 0.00 0.60 127.0.0.1 osqa.informs.org OPTIONS * HTTP/1.0 4-0 - 0/0/20 . 0.45 356 9 0.0 0.00 0.31 127.0.0.1 osqa.informs.org OPTIONS * HTTP/1.0 5-0 18852 0/16/34 _ 0.98 27 18120 0.0 0.37 0.62 69.180.250.36 osqa.informs.org GET /questions/289/what-is-the-difference-between-operations-re 6-0 - 0/0/32 . 0.94 309 29 0.0 0.00 0.64 127.0.0.1 osqa.informs.org OPTIONS * HTTP/1.0 7-0 - 0/0/31 . 1.15 382 32 0.0 0.00 0.75 127.0.0.1 osqa.informs.org OPTIONS * HTTP/1.0 8-0 - 0/0/21 . 0.28 403 19 0.0 0.00 0.20 127.0.0.1 osqa.informs.org OPTIONS * HTTP/1.0 9-0 - 0/0/32 . 1.37 288 16 0.0 0.00 0.60 127.0.0.1 osqa.informs.org OPTIONS * HTTP/1.0 10-0 - 0/0/33 . 1.72 383 16 0.0 0.00 0.40 127.0.0.1 osqa.informs.org OPTIONS * HTTP/1.0 I am running Django 1.3 This is a mod_wsgi configuration and copied is the wsgi.conf file: <IfModule !python_module> <IfModule !wsgi_module> LoadModule wsgi_module modules/mod_wsgi.so <IfModule wsgi_module> <Directory /var/www/osqa> Order allow,deny Allow from all #Deny from all </Directory> WSGISocketPrefix /var/run/wsgi WSGIPythonEggs /var/tmp WSGIDaemonProcess OSQA maximum-requests=10000 WSGIProcessGroup OSQA Alias /admin_media/ /usr/lib/python2.6/site-packages/Django-1.2.5-py2.6.egg/django/contrib/admin/media/ Alias /m/ /var/www/osqa/forum/skins/ Alias /upfiles/ /var/www/osqa/forum/upfiles/ <Directory /var/www/osqa/forum/skins> Order allow,deny Allow from all </Directory> WSGIScriptAlias / /var/www/osqa/osqa.wsgi </IfModule> </IfModule> </IfModule> This is the httpd.conf file Timeout 120 KeepAlive Off MaxKeepAliveRequests 100 MaxKeepAliveRequests 400 KeepAliveTimeout 3 <IfModule prefork.c> Startservers 15 MinSpareServers 10 MaxSpareServers 20 ServerLimit 50 MaxClients 50 MaxRequestsPerChild 0 </IfModule> <IfModule worker.c> StartServers 4 MaxClients 150 MinSpareThreads 25 MaxSpareThreads 75 ThreadsPerChild 25 MaxRequestsPerChild 0 </IfModule> We are using MySQL The server is an ESX4i, configured for the VM to use 4 CPUs and 8 GB Ram. Hyper threading is enabled, 2 physical CPU's, with 4 Logical. the CPU are Intel Xeon 2.8 GHz. Total memory is 12GB

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• what is best config for nginx worker_rlimit_nofile and worker_connections 28672

  - by Binh Nguyen

  i have issue of web-brower response ( especially on ie ) very slow, some time time out, and sometime hang out up to 20 seconds for one file redirect 301 when test with "f12 derverloper tool of ie" .. it report wait/start time very long. but after got connected the elements on web weill be dowload and show out fast ( test at xaluan.com ) It most happen when active user on web more than 2100 ( use google real time live analytic ). server running cenos 5 with ngix, apache, 32core cpu, 96G ram, raid 10 sas hdd.. == flowing is my config == user nobody; # no need for more workers in the proxy mode worker_processes 28; #old 32 #good at 24 error_log /var/log/nginx/error.log; #old add in end: info worker_rlimit_nofile 22528; events { worker_connections 22528; use epoll; # you should use epoll here for Linux kernels 2.6.x } http { server_name_in_redirect off; server_names_hash_max_size 10240; server_names_hash_bucket_size 1024; include mime.types; default_type application/octet-stream; server_tokens off; disable_symlinks off; sendfile on; tcp_nopush on; tcp_nodelay on; server_name_in_redirect off; server_names_hash_max_size 10240; server_names_hash_bucket_size 1024; include mime.types; default_type application/octet-stream; server_tokens off; disable_symlinks off; sendfile on; tcp_nopush on; tcp_nodelay on; keepalive_timeout 25; #old 5 gzip on; #old on gzip_vary on; gzip_disable "MSIE [1-6]\."; gzip_proxied any; gzip_http_version 1.1; gzip_min_length 1000; gzip_comp_level 6; gzip_buffers 16 8k; ignore_invalid_headers on; client_header_timeout 1m; #3m client_body_timeout 1m; #3m send_timeout 1m; #3m reset_timedout_connection on; connection_pool_size 256; client_header_buffer_size 256k; large_client_header_buffers 4 256k; client_max_body_size 100M; client_body_buffer_size 256k; request_pool_size 32k; output_buffers 4 32k; postpone_output 1460; proxy_temp_path /tmp/nginx_proxy/; client_body_in_file_only on; log_format bytes_log "$msec $bytes_sent ."; limit_conn_zone $binary_remote_addr zone=limit_per_ip:1m; limit_conn limit_per_ip 20; limit_req_zone $binary_remote_addr zone=allips:5m rate=200r/s; limit_req zone=allips burst=200 nodelay; include "/etc/nginx/vhosts/*"; } =========== I have play around with worker config 1- tried increase as some one suggess: worker_rlimit_nofile = worker_connections = worker_processes * 1024 = 32768 2- tried to set low: worker_processes = 28 and other worker at 22582 and other solution too .. but not work cause some time it make server load hight very quick 3- tried to comment out the # worker_rlimit_nofile . so it will be unlimited. it look like solved a bit about issue response time. but it also make server high load quick in peak time... Please help thanks PS: other apache you may have look for help me out thanks Listen 0.0.0.0:8081 User nobody Group nobody ExtendedStatus On ServerAdmin [email protected] ServerName server.xaluan.com LogLevel warn # These can be set in WHM under 'Apache Global Configuration' Timeout 100 TraceEnable Off ServerSignature Off ServerTokens ProductOnly FileETag None StartServers 15 <IfModule prefork.c> MinSpareServers 20 MaxSpareServers 50 #MaxSpareServers 40 </IfModule> ServerLimit 1572 MaxClients 1572 MaxRequestsPerChild 4000 # MaxRequestsPerChild 3000 KeepAlive On KeepAliveTimeout 3 MaxKeepAliveRequests 300 #MaxKeepAliveRequests 130

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• The Proper Use of the VM Role in Windows Azure

  - by BuckWoody

  At the Professional Developer’s Conference (PDC) in 2010 we announced an addition to the Computational Roles in Windows Azure, called the VM Role. This new feature allows a great deal of control over the applications you write, but some have confused it with our full infrastructure offering in Windows Hyper-V. There is a proper architecture pattern for both of them. Virtualization Virtualization is the process of taking all of the hardware of a physical computer and replicating it in software alone. This means that a single computer can “host” or run several “virtual” computers. These virtual computers can run anywhere - including at a vendor’s location. Some companies refer to this as Cloud Computing since the hardware is operated and maintained elsewhere. IaaS The more detailed definition of this type of computing is called Infrastructure as a Service (Iaas) since it removes the need for you to maintain hardware at your organization. The operating system, drivers, and all the other software required to run an application are still under your control and your responsibility to license, patch, and scale. Microsoft has an offering in this space called Hyper-V, that runs on the Windows operating system. Combined with a hardware hosting vendor and the System Center software to create and deploy Virtual Machines (a process referred to as provisioning), you can create a Cloud environment with full control over all aspects of the machine, including multiple operating systems if you like. Hosting machines and provisioning them at your own buildings is sometimes called a Private Cloud, and hosting them somewhere else is often called a Public Cloud. State-ful and Stateless Programming This paradigm does not create a new, scalable way of computing. It simply moves the hardware away. The reason is that when you limit the Cloud efforts to a Virtual Machine, you are in effect limiting the computing resources to what that single system can provide. This is because much of the software developed in this environment maintains “state” - and that requires a little explanation. “State-ful programming” means that all parts of the computing environment stay connected to each other throughout a compute cycle. The system expects the memory, CPU, storage and network to remain in the same state from the beginning of the process to the end. You can think of this as a telephone conversation - you expect that the other person picks up the phone, listens to you, and talks back all in a single unit of time. In “Stateless” computing the system is designed to allow the different parts of the code to run independently of each other. You can think of this like an e-mail exchange. You compose an e-mail from your system (it has the state when you’re doing that) and then you walk away for a bit to make some coffee. A few minutes later you click the “send” button (the network has the state) and you go to a meeting. The server receives the message and stores it on a mail program’s database (the mail server has the state now) and continues working on other mail. Finally, the other party logs on to their mail client and reads the mail (the other user has the state) and responds to it and so on. These events might be separated by milliseconds or even days, but the system continues to operate. The entire process doesn’t maintain the state, each component does. This is the exact concept behind coding for Windows Azure. The stateless programming model allows amazing rates of scale, since the message (think of the e-mail) can be broken apart by multiple programs and worked on in parallel (like when the e-mail goes to hundreds of users), and only the order of re-assembling the work is important to consider. For the exact same reason, if the system makes copies of those running programs as Windows Azure does, you have built-in redundancy and recovery. It’s just built into the design. The Difference Between Infrastructure Designs and Platform Designs When you simply take a physical server running software and virtualize it either privately or publicly, you haven’t done anything to allow the code to scale or have recovery. That all has to be handled by adding more code and more Virtual Machines that have a slight lag in maintaining the running state of the system. Add more machines and you get more lag, so the scale is limited. This is the primary limitation with IaaS. It’s also not as easy to deploy these VM’s, and more importantly, you’re often charged on a longer basis to remove them. your agility in IaaS is more limited. Windows Azure is a Platform - meaning that you get objects you can code against. The code you write runs on multiple nodes with multiple copies, and it all works because of the magic of Stateless programming. you don’t worry, or even care, about what is running underneath. It could be Windows (and it is in fact a type of Windows Server), Linux, or anything else - but that' isn’t what you want to manage, monitor, maintain or license. You don’t want to deploy an operating system - you want to deploy an application. You want your code to run, and you don’t care how it does that. Another benefit to PaaS is that you can ask for hundreds or thousands of new nodes of computing power - there’s no provisioning, it just happens. And you can stop using them quicker - and the base code for your application does not have to change to make this happen. Windows Azure Roles and Their Use If you need your code to have a user interface, in Visual Studio you add a Web Role to your project, and if the code needs to do work that doesn’t involve a user interface you can add a Worker Role. They are just containers that act a certain way. I’ll provide more detail on those later. Note: That’s a general description, so it’s not entirely accurate, but it’s accurate enough for this discussion. So now we’re back to that VM Role. Because of the name, some have mistakenly thought that you can take a Virtual Machine running, say Linux, and deploy it to Windows Azure using this Role. But you can’t. That’s not what it is designed for at all. If you do need that kind of deployment, you should look into Hyper-V and System Center to create the Private or Public Infrastructure as a Service. What the VM Role is actually designed to do is to allow you to have a great deal of control over the system where your code will run. Let’s take an example. You’ve heard about Windows Azure, and Platform programming. You’re convinced it’s the right way to code. But you have a lot of things you’ve written in another way at your company. Re-writing all of your code to take advantage of Windows Azure will take a long time. Or perhaps you have a certain version of Apache Web Server that you need for your code to work. In both cases, you think you can (or already have) code the the software to be “Stateless”, you just need more control over the place where the code runs. That’s the place where a VM Role makes sense. Recap Virtualizing servers alone has limitations of scale, availability and recovery. Microsoft’s offering in this area is Hyper-V and System Center, not the VM Role. The VM Role is still used for running Stateless code, just like the Web and Worker Roles, with the exception that it allows you more control over the environment of where that code runs.

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• nginx problem accessing virtual hosts

  - by Sc0rian

  I am setting up nginx as a reverse proxy. The server runs on directadmin and lamp stack. I have nginx running on port 81. I can access all my sites (including virtual ips) on the port 81. However when I forward the traffic from port 80 to 81, the virtual ips have a message saying "Apache is running normally". Server IPs are fine, and I can still access virtual IP's on 81. [root@~]# netstat -an | grep LISTEN | egrep ":80|:81" tcp 0 0 <virtual ip>:81 0.0.0.0:* LISTEN tcp 0 0 <virtual ip>:81 0.0.0.0:* LISTEN tcp 0 0 <serverip>:81 0.0.0.0:* LISTEN tcp 0 0 :::80 :::* LISTEN apache 24090 0.6 1.3 29252 13612 ? S 18:34 0:00 /usr/sbin/httpd -k start -DSSL apache 24092 0.9 2.1 39584 22056 ? S 18:34 0:00 /usr/sbin/httpd -k start -DSSL apache 24096 0.2 1.9 35892 20256 ? S 18:34 0:00 /usr/sbin/httpd -k start -DSSL apache 24120 0.3 1.7 35752 17840 ? S 18:34 0:00 /usr/sbin/httpd -k start -DSSL apache 24495 0.0 1.4 30892 14756 ? S 18:35 0:00 /usr/sbin/httpd -k start -DSSL apache 24496 1.0 2.1 39892 22164 ? S 18:35 0:00 /usr/sbin/httpd -k start -DSSL apache 24516 1.5 3.6 55496 38040 ? S 18:35 0:00 /usr/sbin/httpd -k start -DSSL apache 24519 0.1 1.2 28996 13224 ? S 18:35 0:00 /usr/sbin/httpd -k start -DSSL apache 24521 2.7 4.0 58244 41984 ? S 18:35 0:00 /usr/sbin/httpd -k start -DSSL apache 24522 0.0 1.2 29124 12672 ? S 18:35 0:00 /usr/sbin/httpd -k start -DSSL apache 24524 0.0 1.1 28740 12364 ? S 18:35 0:00 /usr/sbin/httpd -k start -DSSL apache 24535 1.1 1.7 36008 17876 ? S 18:35 0:00 /usr/sbin/httpd -k start -DSSL apache 24536 0.0 1.1 28592 12084 ? S 18:35 0:00 /usr/sbin/httpd -k start -DSSL apache 24537 0.0 1.1 28592 12112 ? S 18:35 0:00 /usr/sbin/httpd -k start -DSSL apache 24539 0.0 0.0 0 0 ? Z 18:35 0:00 [httpd] <defunct> apache 24540 0.0 1.1 28592 11540 ? S 18:35 0:00 /usr/sbin/httpd -k start -DSSL apache 24541 0.0 1.1 28592 11548 ? S 18:35 0:00 /usr/sbin/httpd -k start -DSSL root 24548 0.0 0.0 4132 752 pts/0 R+ 18:35 0:00 egrep apache|nginx root 28238 0.0 0.0 19576 284 ? Ss May29 0:00 nginx: master process /usr/local/nginx/sbin/nginx -c /usr/local/nginx/conf/nginx.conf apache 28239 0.0 0.0 19888 804 ? S May29 0:00 nginx: worker process apache 28240 0.0 0.0 19888 548 ? S May29 0:00 nginx: worker process apache 28241 0.0 0.0 19736 484 ? S May29 0:00 nginx: cache manager process here is my nginx conf: cat /usr/local/nginx/conf/nginx.conf user apache apache; worker_processes 2; # Set it according to what your CPU have. 4 Cores = 4 worker_rlimit_nofile 8192; pid /var/run/nginx.pid; events { worker_connections 1024; } http { include mime.types; default_type application/octet-stream; log_format main '$remote_addr - $remote_user [$time_local] ' '"$request" $status $body_bytes_sent "$http_referer" ' '"$http_user_agent" "$http_x_forwarded_for"'; server_tokens off; access_log /var/log/nginx_access.log main; error_log /var/log/nginx_error.log debug; server_names_hash_bucket_size 64; sendfile on; tcp_nopush on; tcp_nodelay off; keepalive_timeout 30; gzip on; gzip_comp_level 9; gzip_proxied any; proxy_buffering on; proxy_cache_path /usr/local/nginx/proxy_temp levels=1:2 keys_zone=one:15m inactive=7d max_size=1000m; proxy_buffer_size 16k; proxy_buffers 100 8k; proxy_connect_timeout 60; proxy_send_timeout 60; proxy_read_timeout 60; server { listen <server ip>:81 default rcvbuf=8192 sndbuf=16384 backlog=32000; # Real IP here server_name <server host name> _; # "_" is for handle all hosts that are not described by server_name charset off; access_log /var/log/nginx_host_general.access.log main; location / { proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_pass http://<server ip>; # Real IP here client_max_body_size 16m; client_body_buffer_size 128k; proxy_buffering on; proxy_connect_timeout 90; proxy_send_timeout 90; proxy_read_timeout 120; proxy_buffer_size 16k; proxy_buffers 32 32k; proxy_busy_buffers_size 64k; proxy_temp_file_write_size 64k; } location /nginx_status { stub_status on; access_log off; allow 127.0.0.1; deny all; } } include /usr/local/nginx/vhosts/*.conf; } here is my vhost conf: # cat /usr/local/nginx/vhosts/1.conf server { listen <virt ip>:81 default rcvbuf=8192 sndbuf=16384 backlog=32000; # Real IP here server_name <virt domain name>.com ; # "_" is for handle all hosts that are not described by server_name charset off; access_log /var/log/nginx_host_general.access.log main; location / { proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_pass http://<virt ip>; # Real IP here client_max_body_size 16m; client_body_buffer_size 128k; proxy_buffering on; proxy_connect_timeout 90; proxy_send_timeout 90; proxy_read_timeout 120; proxy_buffer_size 16k; proxy_buffers 32 32k; proxy_busy_buffers_size 64k; proxy_temp_file_write_size 64k; } }

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• Developing Mobile Applications: Web, Native, or Hybrid?

  - by Michelle Kimihira

  Authors: Joe Huang, Senior Principal Product Manager, Oracle Mobile Application Development Framework  and Carlos Chang, Senior Principal Product Director The proliferation of mobile devices and platforms represents a game-changing technology shift on a number of levels. Companies must decide not only the best strategic use of mobile platforms, but also how to most efficiently implement them. Inevitably, this conversation devolves to the developers, who face the task of developing and supporting mobile applications—not a simple task in light of the number of devices and platforms. Essentially, developers can choose from the following three different application approaches, each with its own set of pros and cons. Native Applications: This refers to apps built for and installed on a specific platform, such as iOS or Android, using a platform-specific software development kit (SDK).  For example, apps for Apple’s iPhone and iPad are designed to run specifically on iOS and are written in Xcode/Objective-C. Android has its own variation of Java, Windows uses C#, and so on.  Native apps written for one platform cannot be deployed on another. Native apps offer fast performance and access to native-device services but require additional resources to develop and maintain each platform, which can be expensive and time consuming. Mobile Web Applications: Unlike native apps, mobile web apps are not installed on the device; rather, they are accessed via a Web browser.  These are server-side applications that render HTML, typically adjusting the design depending on the type of device making the request.  There are no program coding constraints for writing server-side apps—they can be written in Java, C, PHP, etc., it doesn’t matter.  Instead, the server detects what type of mobile browser is pinging the server and adjusts accordingly. For example, it can deliver fully JavaScript and CSS-enabled content to smartphone browsers, while downgrading gracefully to basic HTML for feature phone browsers. Mobile apps work across platforms, but are limited to what you can do through a browser and require Internet connectivity. For certain types of applications, these constraints may not be an issue. Oracle supports mobile web applications via ADF Faces (for tablets) and ADF Mobile browser (Trinidad) for smartphone and feature phones. Hybrid Applications: As the name implies, hybrid apps combine technologies from native and mobile Web apps to gain the benefits each. For example, these apps are installed on a device, like their pure native app counterparts, while the user interface (UI) is based on HTML5.  This UI runs locally within the native container, which usually leverages the device’s browser engine.  The advantage of using HTML5 is a consistent, cross-platform UI that works well on most devices.  Combining this with the native container, which is installed on-device, provides mobile users with access to local device services, such as camera, GPS, and local device storage.  Native apps may offer greater flexibility in integrating with device native services.  However, since hybrid applications already provide device integrations that typical enterprise applications need, this is typically less of an issue.  The new Oracle ADF Mobile release is an HTML5 and Java hybrid framework that targets mobile app development to iOS and Android from one code base. So, Which is the Best Approach? The short answer is – the best choice depends on the type of application you are developing.  For instance, animation-intensive apps such as games would favor native apps, while hybrid applications may be better suited for enterprise mobile apps because they provide multi-platform support. Just for starters, the following issues must be considered when choosing a development path. Application Complexity: How complex is the application? A quick app that accesses a database or Web service for some data to display?  You can keep it simple, and a mobile Web app may suffice. However, for a mobile/field worker type of applications that supports mission critical functionality, hybrid or native applications are typically needed. Richness of User Interactivity: What type of user experience is required for the application?  Mobile browser-based app that’s optimized for mobile UI may suffice for quick lookup or productivity type of applications.  However, hybrid/native application would typically be required to deliver highly interactive user experiences needed for field-worker type of applications.  For example, interactive BI charts/graphs, maps, voice/email integration, etc.  In the most extreme case like gaming applications, native applications may be necessary to deliver the highly animated and graphically intensive user experience. Performance: What type of performance is required by the application functionality?  For instance, for real-time look up of data over the network, mobile app performance depends on network latency and server infrastructure capabilities.  If consistent performance is required, data would typically need to be cached, which is supported on hybrid or native applications only. Connectivity and Availability: What sort of connectivity will your application require? Does the app require Web access all the time in order to always retrieve the latest data from the server? Or do the requirements dictate offline support? While native and hybrid apps can be built to operate offline, Web mobile apps require Web connectivity. Multi-platform Requirements: The terms “consumerization of IT” and BYOD (bring your own device) effectively mean that the line between the consumer and the enterprise devices have become blurred. Employees are bringing their personal mobile devices to work and are often expecting that they work in the corporate network and access back-office applications.  Even if companies restrict access to the big dogs: (iPad, iPhone, Android phones and tablets, possibly Windows Phone and tablets), trying to support each platform natively will require increasing resources and domain expertise with each new language/platform. And let’s not forget the maintenance costs, involved in upgrading new versions of each platform.   Where multi-platform support is needed, Web mobile or hybrid apps probably have the advantage. Going native, and trying to support multiple operating systems may be cost prohibitive with existing resources and developer skills. Device-Services Access:  If your app needs to access local device services, such as the camera, contacts app, accelerometer, etc., then your choices are limited to native or hybrid applications.   Fragmentation: Apple controls Apple iOS and the only concern is what version iOS is running on any given device.   Not so Android, which is open source. There are many, many versions and variants of Android running on different devices, which can be a nightmare for app developers trying to support different devices running different flavors of Android.  (Is it an Amazon Kindle Fire? a Samsung Galaxy?  A Barnes & Noble Nook?) This is a nightmare scenario for native apps—on the other hand, a mobile Web or hybrid app, when properly designed, can shield you from these complexities because they are based on common frameworks.  Resources: How many developers can you dedicate to building and supporting mobile application development?  What are their existing skills sets?  If you’re considering native application development due to the complexity of the application under development, factor the costs of becoming proficient on a each platform’s OS and programming language. Add another platform, and that’s another language, another SDK. On the other side of the equation, Web mobile or hybrid applications are simpler to make, and readily support more platforms, but there may be performance trade-offs. Conclusion This only scratches the surface. However, I hope to have suggested some food for thought in choosing your mobile development strategy.  Do your due diligence, search the Web, read up on mobile, talk to peers, attend events. The development team at Oracle is working hard on mobile technologies to help customers extend enterprise applications to mobile faster and effectively.  To learn more on what Oracle has to offer, check out the Oracle ADF Mobile (hybrid) and ADF Faces/ADF Mobile browser (Web Mobile) solutions from Oracle.   Additional Information Blog: ADF Blog Product Information on OTN: ADF Mobile Product Information on Oracle.com: Oracle Fusion Middleware Follow us on Twitter and Facebook Subscribe to our regular Fusion Middleware Newsletter

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• Christmas in the Clouds

  - by andrewbrust

  I have been spending the last 2 weeks immersing myself in a number of Windows Azure and SQL Azure technologies.  And in setting up a new business (I’ll speak more about that in the future), I have also become a customer of Microsoft’s BPOS (Business Productivity Online Services).  In short, it has been a fortnight of Microsoft cloud computing. On the Azure side, I’ve looked, of course, at Web Roles and Worker Roles.  But I’ve also looked at Azure Storage’s REST API (including coding to it directly), I’ve looked at Azure Drive and the new VM Role; I’ve looked quite a bit at SQL Azure (including the project “Houston” Silverlight UI) and I’ve looked at SQL Azure labs’ OData service too. I’ve also looked at DataMarket and its integration with both PowerPivot and native Excel.  Then there’s AppFabric Caching, SQL Azure Reporting (what I could learn of it) and the Visual Studio tooling for Azure, including the storage of certificate-based credentials.  And to round it out with some user stuff, on the BPOS side, I’ve been working with Exchange Online, SharePoint Online and LiveMeeting. I have to say I like a lot of what I’ve been seeing.  Azure’s not perfect, and BPOS certainly isn’t either.  But there’s good stuff in all these products, and there’s a lot of value. Azure Goes Deep Most people know that Web and Worker roles put the platform in charge of spinning virtual machines up and down, and keeping them up to date. But you can go way beyond that now.  The still-in-beta VM Role gives you the power to craft the machine (much as does Amazon’s EC2), though it takes away the platform’s self-managing attributes.  It still spins instances up and down, making drive storage non-durable, but Azure Drive gives you the ability to store VHD files as blobs and mount them as virtual hard drives that are readable and writeable.  Whether with Azure Storage or SQL Azure, Azure does data.  And OData is everywhere.  Azure Table Storage supports an OData Interface.  So does SQL Azure and so does DataMarket (the former project “Dallas”).  That means that Azure data repositories aren’t just straightforward to provision and configure…they’re also easy to program against, from just about any programming environment, in a RESTful manner.  And for more .NET-centric implementations, Azure AppFabric caching takes the technology formerly known as “Velocity” and throws it up into the cloud, speeding data access even more. Snapping in Place Once you get the hang of it, this stuff just starts to work in a way that becomes natural to understand.  I wasn’t expecting that, and I was really happy to discover it. In retrospect, I am not surprised, because I think the various Azure teams are the center of gravity for Redmond’s innovation right now.  The products belie this and so do my observations of the product teams’ motivation and high morale.  It is really good to see this; Microsoft needs to lead somewhere, and they need to be seen as the underdog while doing so.  With Azure, both requirements are in place.   BPOS: Bad Acronym, Easy Setup BPOS is about products you already know; Exchange, SharePoint, Live Meeting and Office Communications Server.  As such, it’s hard not to be underwhelmed by BPOS.  Until you realize how easy it makes it to get all that stuff set up.  I would say that from sign-up to productive use took me about 45 minutes…and that included the time necessary to wrestle with my DNS provider, set up Outlook and my SmartPhone up to talk to the Exchange account, create my SharePoint site collection, and configure the Outlook Conferencing add-in to talk to the provisioned Live Meeting account. Never before did I think setting up my own Exchange mail could come anywhere close to the simplicity of setting up an SMTP/POP account, and yet BPOS actually made it faster.   What I want from my Azure Christmas Next Year Not everything about Microsoft’s cloud is good.  I close this post with a list of things I’d like to see addressed: BPOS offerings are still based on the 2007 Wave of Microsoft server technologies.  We need to get to 2010, and fast.  Arguably, the 2010 products should have been released to the off-premises channel before the on-premise sone.  Office 365 can’t come fast enough. Azure’s Internet tooling and domain naming, is scattered and confusing.  Deployed ASP.NET applications go to cloudapp.net; SQL Azure and Azure storage work off windows.net.  The Azure portal and Project Houston are at azure.com.  Then there’s appfabriclabs.com and sqlazurelabs.com.  There is a new Silverlight portal that replaces most, but not all of the HTML ones.  And Project Houston is Silvelright-based too, though separate from the Silverlight portal tooling. Microsoft is the king off tooling.  They should not make me keep an entire OneNote notebook full of portal links, account names, access keys, assemblies and namespaces and do so much CTRL-C/CTRL-V work.  I’d like to see more project templates, have them automatically reference the appropriate assemblies, generate the right using/Imports statements and prime my config files with the right markup.  Then I want a UI that lets me log in with my Live ID and pick the appropriate project, database, namespace and key string to get set up fast. Beta programs, if they’re open, should onboard me quickly.  I know the process is difficult and everyone’s going as fast as they can.  But I don’t know why it’s so difficult or why it takes so long.  Getting developers up to speed on new features quickly helps popularize the platform.  Make this a priority. Make Azure accessible from the simplicity platforms, i.e. ASP.NET Web Pages (Razor) and LightSwitch.  Support .NET 4 now.  Make WebMatrix, IIS Express and SQL Compact work with the Azure development fabric. Have HTML helpers make Azure programming easier.  Have LightSwitch work with SQL Azure and not require SQL Express.  LightSwitch has some promising Azure integration now.  But we need more.  WebMatrix has none and that’s just silly, now that the Extra Small Instance is being introduced. The Windows Azure Platform Training Kit is great.  But I want Microsoft to make it even better and I want them to evangelize it much more aggressively.  There’s a lot of good material on Azure development out there, but it’s scattered in the same way that the platform is.   The Training Kit ties a lot of disparate stuff together nicely.  Make it known. Should Old Acquaintance Be Forgot All in all, diving deep into Azure was a good way to end the year.  Diving deeper into Azure should a great way to spend next year, not just for me, but for Microsoft too.

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• SQL Server Table Polling by Multiple Subscribers

  - by Daniel Hester

  Background Designing Stored Procedures that are safe for multiple subscribers (to call simultaneously) can be challenging.  For example let’s say that you want multiple worker processes to poll a shared work queue that’s encapsulated as a SQL Table. This is a common scenario and through experience you’ll find that you want to use Table Hints to prevent unwanted locking when performing simultaneous queries on the same table. There are three table hints to consider: NOLOCK, READPAST and UPDLOCK. Both NOLOCK and READPAST table hints allow you to SELECT from a table without placing a LOCK on that table. However, SELECTs with the READPAST hint will ignore any records that are locked due to being updated/inserted (or otherwise “dirty”), whereas a SELECT with NOLOCK ignores all locks including dirty reads. For the initial update of the flag (that marks the record as available for subscription) I don’t use the NOLOCK Table Hint because I want to be sensitive to the “active” records in the table and I want to exclude them.  I use an Update Lock (UPDLOCK) in conjunction with a WHERE clause that uses a sub-select with a READPAST Table Hint in order to explicitly lock the records I’m updating (UPDLOCK) but not place a lock on the table when selecting the records that I’m going to update (READPAST). UPDATES should be allowed to lock the rows affected because we’re probably changing a flag on a record so that it is not included in a SELECT from another subscriber. On the UPDATE statement we should explicitly use the UPDLOCK to guard against lock escalation. A SELECT to check for the next record(s) to process can result in a shared read lock being held by more than one subscriber polling the shared work queue (SQL table). It is expected that more than one worker process (or server) might try to process the same new record(s) at the same time. When each process then tries to obtain the update lock, none of them can because another process has a shared read lock in place. Thus without the UPDLOCK hint the result would be a lock escalation deadlock; however with the UPDLOCK hint this condition is mitigated against. Note that using the READPAST table hint requires that you also set the ISOLATION LEVEL of the transaction to be READ COMMITTED (rather than the default of SERIALIZABLE). Guidance In the Stored Procedure that returns records to the multiple subscribers: Perform the UPDATE first. Change the flag that makes the record available to subscribers.  Additionally, you may want to update a LastUpdated datetime field in order to be able to check for records that “got stuck” in an intermediate state or for other auditing purposes. In the UPDATE statement use the (UPDLOCK) Table Hint on the UPDATE statement to prevent lock escalation. In the UPDATE statement also use a WHERE Clause that uses a sub-select with a (READPAST) Table Hint to select the records that you’re going to update. In the UPDATE statement use the OUTPUT clause in conjunction with a Temporary Table to isolate the record(s) that you’ve just updated and intend to return to the subscriber. This is the fastest way to update the record(s) and to get the records’ identifiers within the same operation. Finally do a set-based SELECT on the main Table (using the Temporary Table to identify the records in the set) with either a READPAST or NOLOCK table hint.  Use NOLOCK if there are other processes (besides the multiple subscribers) that might be changing the data that you want to return to the multiple subscribers; or use READPAST if you're sure there are no other processes (besides the multiple subscribers) that might be updating column data in the table for other purposes (e.g. changes to a person’s last name).  NOLOCK is generally the better fit in this part of the scenario. See the following as an example: CREATE PROCEDURE [dbo].[usp_NewCustomersSelect] AS BEGIN -- OVERRIDE THE DEFAULT ISOLATION LEVEL SET TRANSACTION ISOLATION LEVEL READ COMMITTED -- SET NOCOUNT ON SET NOCOUNT ON -- DECLARE TEMP TABLE -- Note that this example uses CustomerId as an identifier; -- you could just use the Identity column Id if that’s all you need. DECLARE @CustomersTempTable TABLE ( CustomerId NVARCHAR(255) ) -- PERFORM UPDATE FIRST -- [Customers] is the name of the table -- [Id] is the Identity Column on the table -- [CustomerId] is the business document key used to identify the -- record globally, i.e. in other systems or across SQL tables -- [Status] is INT or BIT field (if the status is a binary state) -- [LastUpdated] is a datetime field used to record the time of the -- last update UPDATE [Customers] WITH (UPDLOCK) SET [Status] = 1, [LastUpdated] = GETDATE() OUTPUT [INSERTED].[CustomerId] INTO @CustomersTempTable WHERE ([Id] = (SELECT TOP 100 [Id] FROM [Customers] WITH (READPAST) WHERE ([Status] = 0) ORDER BY [Id] ASC)) -- PERFORM SELECT FROM ENTITY TABLE SELECT [C].[CustomerId], [C].[FirstName], [C].[LastName], [C].[Address1], [C].[Address2], [C].[City], [C].[State], [C].[Zip], [C].[ShippingMethod], [C].[Id] FROM [Customers] AS [C] WITH (NOLOCK), @CustomersTempTable AS [TEMP] WHERE ([C].[CustomerId] = [TEMP].[CustomerId]) END In a system that has been designed to have multiple status values for records that need to be processed in the Work Queue it is necessary to have a “Watch Dog” process by which “stale” records in intermediate states (such as “In Progress”) are detected, i.e. a [Status] of 0 = New or Unprocessed; a [Status] of 1 = In Progress; a [Status] of 2 = Processed; etc.. Thus, if you have a business rule that states that the application should only process new records if all of the old records have been processed successfully (or marked as an error), then it will be necessary to build a monitoring process to detect stalled or stale records in the Work Queue, hence the use of the LastUpdated column in the example above. The Status field along with the LastUpdated field can be used as the criteria to detect stalled / stale records. It is possible to put this watchdog logic into the stored procedure above, but I would recommend making it a separate monitoring function. In writing the stored procedure that checks for stale records I would recommend using the same kind of lock semantics as suggested above. The example below looks for records that have been in the “In Progress” state ([Status] = 1) for greater than 60 seconds: CREATE PROCEDURE [dbo].[usp_NewCustomersWatchDog] AS BEGIN -- TO OVERRIDE THE DEFAULT ISOLATION LEVEL SET TRANSACTION ISOLATION LEVEL READ COMMITTED -- SET NOCOUNT ON SET NOCOUNT ON DECLARE @MaxWait int; SET @MaxWait = 60 IF EXISTS (SELECT 1 FROM [dbo].[Customers] WITH (READPAST) WHERE ([Status] = 1) AND (DATEDIFF(s, [LastUpdated], GETDATE()) > @MaxWait)) BEGIN SELECT 1 AS [IsWatchDogError] END ELSE BEGIN SELECT 0 AS [IsWatchDogError] END END Downloads The zip file below contains two SQL scripts: one to create a sample database with the above stored procedures and one to populate the sample database with 10,000 sample records.  I am very grateful to Red-Gate software for their excellent SQL Data Generator tool which enabled me to create these sample records in no time at all. References http://msdn.microsoft.com/en-us/library/ms187373.aspx http://www.techrepublic.com/article/using-nolock-and-readpast-table-hints-in-sql-server/6185492 http://geekswithblogs.net/gwiele/archive/2004/11/25/15974.aspx http://grounding.co.za/blogs/romiko/archive/2009/03/09/biztalk-sql-receive-location-deadlocks-dirty-reads-and-isolation-levels.aspx

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• Exception Handling And Other Contentious Political Topics

  - by Justin Jones

  So about three years ago, around the time of my last blog post, I promised a friend I would write this post. Keeping promises is a good thing, and this is my first step towards easing back into regular blogging. I fully expect him to return from Pennsylvania to buy me a beer over this. However, it’s been an… ahem… eventful three years or so, and blogging, unfortunately, got pushed to the back burner on my priority list, along with a few other career minded activities. Now that the personal drama of the past three years is more or less resolved, it’s time to put a few things back on the front burner. What I consider to be proper exception handling practices is relatively well known these days. There are plenty of blog posts out there already on this topic which more or less echo my opinions on this topic. I’ll try to include a few links at the bottom of the post. Several years ago I had an argument with a co-worker who posited that exceptions should be caught at every level and logged. This might seem like sanity on the surface, but the resulting error log looked something like this: Error: System.SomeException Followed by small stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace.   These were all the same exception. The problem with this approach is that the error log, if you run any kind of analytics on in, becomes skewed depending on how far up the stack trace your exception was thrown. To mitigate this problem, we came up with the concept of the “PreLoggedException”. Basically, we would log the exception at the very top level and subsequently throw the exception back up the stack encapsulated in this pre-logged type, which our logging system knew to ignore. Now the error log looked like this: Error: System.SomeException Followed by small stack trace. Much cleaner, right? Well, there’s still a problem. When your exception happens in production and you go about trying to figure out what happened, you’ve lost more or less all context for where and how this exception was thrown, because all you really know is what method it was thrown in, but really nothing about who was calling the method or why. What gives you this clue is the entire stack trace, which we’re losing here. I believe that was further mitigated by having the logging system pull a system stack trace and add it to the log entry, but what you’re actually getting is the stack for how you got to the logging code. You’re still losing context about the actual error. Not to mention you’re executing a whole slew of catch blocks which are sloooooooowwwww……… In other words, we started with a bad idea and kept band-aiding it until it didn’t suck quite so bad. When I argued for not catching exceptions at every level but rather catching them following a certain set of rules, my co-worker warned me “do yourself a favor, never express that view in any future interviews.” I suppose this is my ultimate dismissal of that advice, but I’m not too worried. My approach for exception handling follows three basic rules: Only catch an exception if 1. You can do something about it. 2. You can add useful information to it. 3. You’re at an application boundary. Here’s what that means: 1. Only catch an exception if you can do something about it. We’ll start with a trivial example of a login system that uses a file. Please, never actually do this in production code, it’s just concocted example. So if our code goes to open a file and the file isn’t there, we get a FileNotFound exception. If the calling code doesn’t know what to do with this, it should bubble up. However, if we know how to create the file from scratch we can create the file and continue on our merry way. When you run into situations like this though, What should really run through your head is “How can I avoid handling an exception at all?” In this case, it’s a trivial matter to simply check for the existence of the file before trying to open it. If we detect that the file isn’t there, we can accomplish the same thing without having to handle in in a catch block. 2. Only catch an exception if you can do something about it. Continuing with the poorly thought out file based login system we contrived in part 1, if the code calls a Login(…) method and the FileNotFound exception is thrown higher up the stack, the code that calls Login must account for a FileNotFound exception. This is kind of counterintuitive because the calling code should not need to know the internals of the Login method, and the data file is an implementation detail. What makes more sense, assuming that we didn’t implement any of the good advice from step 1, is for Login to catch the FileNotFound exception and wrap it in a new exception. For argument’s sake we’ll say LoginSystemFailureException. (Sorry, couldn’t think of anything better at the moment.) This gives us two stack traces, preserving the original stack trace in the inner exception, and also is much more informative to the calling code. 3. Only catch an exception if you’re at an application boundary. At some point we have to catch all the exceptions, even the ones we don’t know what to do with. WinForms, ASP.Net, and most other UI technologies have some kind of built in mechanism for catching unhandled exceptions without fatally terminating the application. It’s still a good idea to somehow gracefully exit the application in this case if possible though, because you can no longer be sure what state your application is in, but nothing annoys a user more than an application just exploding. These unhandled exceptions need to be logged, and this is a good place to catch them. Ideally you never want this option to be exercised, but code as though it will be. When you log these exceptions, give them a “Fatal” status (e.g. Log4Net) and make sure these bugs get handled in your next release. That’s it in a nutshell. If you do it right each exception will only get logged once and with the largest stack trace possible which will make those 2am emergency severity 1 debugging sessions much shorter and less frustrating. Here’s a few people who also have interesting things to say on this topic:  http://blogs.msdn.com/b/ericlippert/archive/2008/09/10/vexing-exceptions.aspx http://www.codeproject.com/Articles/9538/Exception-Handling-Best-Practices-in-NET I know there’s more but I can’t find them at the moment.

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• Windows Azure – Write, Run or Use Software

  - by BuckWoody

  Windows Azure is a platform that has you covered, whether you need to write software, run software that is already written, or Install and use “canned” software whether you or someone else wrote it. Like any platform, it’s a set of tools you can use where it makes sense to solve a problem. The primary location for Windows Azure information is located at http://windowsazure.com. You can find everything there from the development kits for writing software to pricing, licensing and tutorials on all of that. I have a few links here for learning to use Windows Azure – although it’s best if you focus not on the tools, but what you want to solve. I’ve got it broken down here into various sections, so you can quickly locate things you want to know. I’ll include resources here from Microsoft and elsewhere – I use these same resources in the Architectural Design Sessions (ADS) I do with my clients worldwide. Write Software Also called “Platform as a Service” (PaaS), Windows Azure has lots of components you can use together or separately that allow you to write software in .NET or various Open Source languages to work completely online, or in partnership with code you have on-premises or both – even if you’re using other cloud providers. Keep in mind that all of the features you see here can be used together, or independently. For instance, you might only use a Web Site, or use Storage, but you can use both together. You can access all of these components through standard REST API calls, or using our Software Development Kit’s API’s, which are a lot easier. In any case, you simply use Visual Studio, Eclipse, Cloud9 IDE, or even a text editor to write your code from a Mac, PC or Linux.  Components you can use: Azure Web Sites: Windows Azure Web Sites allow you to quickly write an deploy websites, without setting a Virtual Machine, installing a web server or configuring complex settings. They work alone, with other Windows Azure Web Sites, or with other parts of Windows Azure. Web and Worker Roles: Windows Azure Web Roles give you a full stateless computing instance with Internet Information Services (IIS) installed and configured. Windows Azure Worker Roles give you a full stateless computing instance without Information Services (IIS) installed, often used in a "Services" mode. Scale-out is achieved either manually or programmatically under your control. Storage: Windows Azure Storage types include Blobs to store raw binary data, Tables to use key/value pair data (like NoSQL data structures), Queues that allow interaction between stateless roles, and a relational SQL Server database. Other Services: Windows Azure has many other services such as a security mechanism, a Cache (memcacheD compliant), a Service Bus, a Traffic Manager and more. Once again, these features can be used with a Windows Azure project, or alone based on your needs. Various Languages: Windows Azure supports the .NET stack of languages, as well as many Open-Source languages like Java, Python, PHP, Ruby, NodeJS, C++ and more.   Use Software Also called “Software as a Service” (SaaS) this often means consumer or business-level software like Hotmail or Office 365. In other words, you simply log on, use the software, and log off – there’s nothing to install, and little to even configure. For the Information Technology professional, however, It’s not quite the same. We want software that provides services, but in a platform. That means we want things like Hadoop or other software we don’t want to have to install and configure.  Components you can use: Kits: Various software “kits” or packages are supported with just a few clicks, such as Umbraco, Wordpress, and others. Windows Azure Media Services: Windows Azure Media Services is a suite of services that allows you to upload media for encoding, processing and even streaming – or even one or more of those functions. We can add DRM and even commercials to your media if you like. Windows Azure Media Services is used to stream large events all the way down to small training videos. High Performance Computing and “Big Data”: Windows Azure allows you to scale to huge workloads using a few clicks to deploy Hadoop Clusters or the High Performance Computing (HPC) nodes, accepting HPC Jobs, Pig and Hive Jobs, and even interfacing with Microsoft Excel. Windows Azure Marketplace: Windows Azure Marketplace offers data and programs you can quickly implement and use – some free, some for-fee.   Run Software Also known as “Infrastructure as a Service” (IaaS), this offering allows you to build or simply choose a Virtual Machine to run server-based software.  Components you can use: Persistent Virtual Machines: You can choose to install Windows Server, Windows Server with Active Directory, with SQL Server, or even SharePoint from a pre-configured gallery. You can configure your own server images with standard Hyper-V technology and load them yourselves – and even bring them back when you’re done. As a new offering, we also even allow you to select various distributions of Linux – a first for Microsoft. Windows Azure Connect: You can connect your on-premises networks to Windows Azure Instances. Storage: Windows Azure Storage can be used as a remote backup, a hybrid storage location and more using software or even hardware appliances.   Decision Matrix With all of these options, you can use Windows Azure to solve just about any computing problem. It’s often hard to know when to use something on-premises, in the cloud, and what kind of service to use. I’ve used a decision matrix in the last couple of years to take a particular problem and choose the proper technology to solve it. It’s all about options – there is no “silver bullet”, whether that’s Windows Azure or any other set of functions. I take the problem, decide which particular component I want to own and control – and choose the column that has that box darkened. For instance, if I have to control the wiring for a solution (a requirement in some military and government installations), that means the “Networking” component needs to be dark, and so I select the “On Premises” column for that particular solution. If I just need the solution provided and I want no control at all, I can look as “Software as a Service” solutions. Security, Pricing, and Other Info  Security: Security is one of the first questions you should ask in any distributed computing environment. We have certification info, coding guidelines and more, even a general “Request for Information” RFI Response already created for you.   Pricing: Are there licenses? How much does this cost? Is there a way to estimate the costs in this new environment? New Features: Many new features were added to Windows Azure - a good roundup of those changes can be found here. Support: Software Support on Virtual Machines, general support.    

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• Using java to create a dynamic rich:panelMenu

  - by Mark Lewis

  Hail This attempt at using component libs to access a Map<String, ArrayList<String>> <rich:panelMenu style="width:35%" mode="ajax" iconExpandedTopGroup="/img/logListIcon.png" iconCollapsedTopGroup="/img/logListIcon.png" iconCollapsedGroup="/img/logListFolderIconClosed.png" iconExpandedGroup="/img/logListFolderIconOpen.png" iconGroupTopPosition="left" iconItem="/img/logFileIcon.png"> <!-- feed iteration --> <ui:repeat items="#{PanelMenu.panelNodes}" var="map"> <rich:panelMenuGroup label="#{map.key}" style="padding-left: 20px;"> <ui:repeat items="${map.value}" var="entry"> <rich:panelMenuItem label="#{entry}" action="#{PanelMenu.updateCurrent}"> <f:param name="current" value="#{entry}" /> </rich:panelMenuItem> </ui:repeat> </rich:panelMenuGroup> </ui:repeat> </rich:panelMenu> <rich:panel style="width:65%" bodyClass="rich-laguna-panel-no-header"> <a4j:outputPanel ajaxRendered="true"> <h:outputText value="#{PanelMenu.currentLog}" id="current" /> </a4j:outputPanel> </rich:panel> resulted in |STDOUT| 2010-03-06 22:46:22,212 | ERROR | [http-8181-2]: Exception in the filter chain javax.servlet.ServletException: com.sun.facelets.component.UIRepeat cannot be cast to org.richfaces.component.UIPanelMenuItem so I think I need to get onto a resource to use FacesContext context = FacesContext.getCurrentInstance(); but as I'm fairly new to both java and jsf I need a bit of help. Can anyone suggest either the (probably small) java method to represent this intention or a really good resource specifically about programming dynamic stuff in RichFaces using java? Naturally I've read the javadocs, but they don't give me a concrete example of some JSF, the associated backing bean java code, and a screen shot of the resulting component. It may be asking a bit much, but I'm sure I'm not alone in thinking that with these three, I'd be able to understand the idea and apply it to many other component types in this family. The RF demo doesn't include dynamic panelMenus or drop downs so I'm a bit stumped. Thanks IA EDIT @BalusC: Thanks for the response, here is complete stack trace: 07-Mar-2010 19:05:52 com.sun.facelets.FaceletViewHandler handleRenderException SEVERE: Error Rendering View[/index.xhtml] java.lang.ClassCastException: com.sun.facelets.component.UIRepeat cannot be cast to org.richfaces.component.UIPanelMenuItem at org.richfaces.renderkit.html.PanelMenuRenderer.insertScript(PanelMenuRenderer.java:141) at org.richfaces.renderkit.html.HtmlPanelMenuRenderer.doEncodeEnd(HtmlPanelMenuRenderer.java:260) at org.richfaces.renderkit.html.HtmlPanelMenuRenderer.doEncodeEnd(HtmlPanelMenuRenderer.java:271) at org.ajax4jsf.renderkit.RendererBase.encodeEnd(RendererBase.java:134) at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:861) at org.ajax4jsf.renderkit.RendererBase.renderChild(RendererBase.java:281) at org.ajax4jsf.renderkit.RendererBase.renderChildren(RendererBase.java:258) at org.richfaces.renderkit.TabRendererBase.encodeChildren(TabRendererBase.java:113) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837) at org.ajax4jsf.renderkit.RendererBase.renderChild(RendererBase.java:277) at org.ajax4jsf.renderkit.RendererBase.renderChildren(RendererBase.java:258) at org.richfaces.renderkit.html.TabPanelRenderer.doEncodeChildren(TabPanelRenderer.java:266) at org.richfaces.renderkit.html.TabPanelRenderer.doEncodeChildren(TabPanelRenderer.java:261) at org.ajax4jsf.renderkit.RendererBase.encodeChildren(RendererBase.java:120) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837) at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:234) at com.sun.faces.renderkit.html_basic.GridRenderer.renderRow(GridRenderer.java:180) at com.sun.faces.renderkit.html_basic.GridRenderer.encodeChildren(GridRenderer.java:127) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837) at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:234) at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:239) at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:239) at com.sun.faces.renderkit.html_basic.GroupRenderer.encodeChildren(GroupRenderer.java:106) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837) at org.ajax4jsf.renderkit.RendererBase.renderChild(RendererBase.java:277) at org.ajax4jsf.renderkit.RendererBase.renderChildren(RendererBase.java:258) at org.richfaces.renderkit.html.PanelRenderer.doEncodeChildren(PanelRenderer.java:200) at org.richfaces.renderkit.html.PanelRenderer.doEncodeChildren(PanelRenderer.java:195) at org.ajax4jsf.renderkit.RendererBase.encodeChildren(RendererBase.java:120) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837) at org.ajax4jsf.renderkit.RendererBase.renderChild(RendererBase.java:277) at org.ajax4jsf.renderkit.RendererBase.renderChildren(RendererBase.java:258) at org.richfaces.renderkit.html.PageRenderer.doEncodeChildren(PageRenderer.java:265) at org.richfaces.renderkit.html.PageRenderer.doEncodeChildren(PageRenderer.java:254) at org.ajax4jsf.renderkit.RendererBase.encodeChildren(RendererBase.java:120) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:930) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:933) at com.sun.facelets.FaceletViewHandler.renderView(FaceletViewHandler.java:594) at org.ajax4jsf.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:100) at org.ajax4jsf.application.AjaxViewHandler.renderView(AjaxViewHandler.java:176) at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:110) at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:100) at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139) at javax.faces.webapp.FacesServlet.service(FacesServlet.java:266) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.ajax4jsf.webapp.BaseXMLFilter.doXmlFilter(BaseXMLFilter.java:178) at org.ajax4jsf.webapp.BaseFilter.handleRequest(BaseFilter.java:290) at org.ajax4jsf.webapp.BaseFilter.processUploadsAndHandleRequest(BaseFilter.java:388) at org.ajax4jsf.webapp.BaseFilter.doFilter(BaseFilter.java:515) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Thread.java:619) 07-Mar-2010 19:05:52 com.sun.faces.lifecycle.Phase doPhase SEVERE: JSF1054: (Phase ID: RENDER_RESPONSE 6, View ID: /index.xhtml) Exception thrown during phase execution: javax.faces.event.PhaseEvent[source=com.sun.faces.lifecycle.LifecycleImpl@30f369] 07-Mar-2010 19:05:52 org.apache.catalina.core.StandardWrapperValve invoke SEVERE: Servlet.service() for servlet Faces Servlet threw exception java.lang.ClassCastException: com.sun.facelets.component.UIRepeat cannot be cast to org.richfaces.component.UIPanelMenuItem at org.richfaces.renderkit.html.PanelMenuRenderer.insertScript(PanelMenuRenderer.java:141) at org.richfaces.renderkit.html.HtmlPanelMenuRenderer.doEncodeEnd(HtmlPanelMenuRenderer.java:260) at org.richfaces.renderkit.html.HtmlPanelMenuRenderer.doEncodeEnd(HtmlPanelMenuRenderer.java:271) at org.ajax4jsf.renderkit.RendererBase.encodeEnd(RendererBase.java:134) at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:861) at org.ajax4jsf.renderkit.RendererBase.renderChild(RendererBase.java:281) at org.ajax4jsf.renderkit.RendererBase.renderChildren(RendererBase.java:258) at org.richfaces.renderkit.TabRendererBase.encodeChildren(TabRendererBase.java:113) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837) at org.ajax4jsf.renderkit.RendererBase.renderChild(RendererBase.java:277) at org.ajax4jsf.renderkit.RendererBase.renderChildren(RendererBase.java:258) at org.richfaces.renderkit.html.TabPanelRenderer.doEncodeChildren(TabPanelRenderer.java:266) at org.richfaces.renderkit.html.TabPanelRenderer.doEncodeChildren(TabPanelRenderer.java:261) at org.ajax4jsf.renderkit.RendererBase.encodeChildren(RendererBase.java:120) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837) at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:234) at com.sun.faces.renderkit.html_basic.GridRenderer.renderRow(GridRenderer.java:180) at com.sun.faces.renderkit.html_basic.GridRenderer.encodeChildren(GridRenderer.java:127) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837) at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:234) at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:239) at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:239) at com.sun.faces.renderkit.html_basic.GroupRenderer.encodeChildren(GroupRenderer.java:106) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837) at org.ajax4jsf.renderkit.RendererBase.renderChild(RendererBase.java:277) at org.ajax4jsf.renderkit.RendererBase.renderChildren(RendererBase.java:258) at org.richfaces.renderkit.html.PanelRenderer.doEncodeChildren(PanelRenderer.java:200) at org.richfaces.renderkit.html.PanelRenderer.doEncodeChildren(PanelRenderer.java:195) at org.ajax4jsf.renderkit.RendererBase.encodeChildren(RendererBase.java:120) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837) at org.ajax4jsf.renderkit.RendererBase.renderChild(RendererBase.java:277) at org.ajax4jsf.renderkit.RendererBase.renderChildren(RendererBase.java:258) at org.richfaces.renderkit.html.PageRenderer.doEncodeChildren(PageRenderer.java:265) at org.richfaces.renderkit.html.PageRenderer.doEncodeChildren(PageRenderer.java:254) at org.ajax4jsf.renderkit.RendererBase.encodeChildren(RendererBase.java:120) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:930) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:933) at com.sun.facelets.FaceletViewHandler.renderView(FaceletViewHandler.java:594) at org.ajax4jsf.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:100) at org.ajax4jsf.application.AjaxViewHandler.renderView(AjaxViewHandler.java:176) at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:110) at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:100) at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139) at javax.faces.webapp.FacesServlet.service(FacesServlet.java:266) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.ajax4jsf.webapp.BaseXMLFilter.doXmlFilter(BaseXMLFilter.java:178) at org.ajax4jsf.webapp.BaseFilter.handleRequest(BaseFilter.java:290) at org.ajax4jsf.webapp.BaseFilter.processUploadsAndHandleRequest(BaseFilter.java:388) at org.ajax4jsf.webapp.BaseFilter.doFilter(BaseFilter.java:515) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Thread.java:619) |STDOUT| 2010-03-07 19:05:52,683 | ERROR | [http-8181-1]: Exception in the filter chain javax.servlet.ServletException: com.sun.facelets.component.UIRepeat cannot be cast to org.richfaces.component.UIPanelMenuItem at javax.faces.webapp.FacesServlet.service(FacesServlet.java:277) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.ajax4jsf.webapp.BaseXMLFilter.doXmlFilter(BaseXMLFilter.java:178) at org.ajax4jsf.webapp.BaseFilter.handleRequest(BaseFilter.java:290) at org.ajax4jsf.webapp.BaseFilter.processUploadsAndHandleRequest(BaseFilter.java:388) at org.ajax4jsf.webapp.BaseFilter.doFilter(BaseFilter.java:515) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Thread.java:619) Caused by: java.lang.ClassCastException: com.sun.facelets.component.UIRepeat cannot be cast to org.richfaces.component.UIPanelMenuItem at org.richfaces.renderkit.html.PanelMenuRenderer.insertScript(PanelMenuRenderer.java:141) at org.richfaces.renderkit.html.HtmlPanelMenuRenderer.doEncodeEnd(HtmlPanelMenuRenderer.java:260) at org.richfaces.renderkit.html.HtmlPanelMenuRenderer.doEncodeEnd(HtmlPanelMenuRenderer.java:271) at org.ajax4jsf.renderkit.RendererBase.encodeEnd(RendererBase.java:134) at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:861) at org.ajax4jsf.renderkit.RendererBase.renderChild(RendererBase.java:281) at org.ajax4jsf.renderkit.RendererBase.renderChildren(RendererBase.java:258) at org.richfaces.renderkit.TabRendererBase.encodeChildren(TabRendererBase.java:113) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837) at org.ajax4jsf.renderkit.RendererBase.renderChild(RendererBase.java:277) at org.ajax4jsf.renderkit.RendererBase.renderChildren(RendererBase.java:258) at org.richfaces.renderkit.html.TabPanelRenderer.doEncodeChildren(TabPanelRenderer.java:266) at org.richfaces.renderkit.html.TabPanelRenderer.doEncodeChildren(TabPanelRenderer.java:261) at org.ajax4jsf.renderkit.RendererBase.encodeChildren(RendererBase.java:120) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837) at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:234) at com.sun.faces.renderkit.html_basic.GridRenderer.renderRow(GridRenderer.java:180) at com.sun.faces.renderkit.html_basic.GridRenderer.encodeChildren(GridRenderer.java:127) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837) at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:234) at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:239) at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:239) at com.sun.faces.renderkit.html_basic.GroupRenderer.encodeChildren(GroupRenderer.java:106) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837) at org.ajax4jsf.renderkit.RendererBase.renderChild(RendererBase.java:277) at org.ajax4jsf.renderkit.RendererBase.renderChildren(RendererBase.java:258) at org.richfaces.renderkit.html.PanelRenderer.doEncodeChildren(PanelRenderer.java:200) at org.richfaces.renderkit.html.PanelRenderer.doEncodeChildren(PanelRenderer.java:195) at org.ajax4jsf.renderkit.RendererBase.encodeChildren(RendererBase.java:120) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837) at org.ajax4jsf.renderkit.RendererBase.renderChild(RendererBase.java:277) at org.ajax4jsf.renderkit.RendererBase.renderChildren(RendererBase.java:258) at org.richfaces.renderkit.html.PageRenderer.doEncodeChildren(PageRenderer.java:265) at org.richfaces.renderkit.html.PageRenderer.doEncodeChildren(PageRenderer.java:254) at org.ajax4jsf.renderkit.RendererBase.encodeChildren(RendererBase.java:120) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:930) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:933) at com.sun.facelets.FaceletViewHandler.renderView(FaceletViewHandler.java:594) at org.ajax4jsf.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:100) at org.ajax4jsf.application.AjaxViewHandler.renderView(AjaxViewHandler.java:176) at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:110) at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:100) at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139) at javax.faces.webapp.FacesServlet.service(FacesServlet.java:266) ... 18 more

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• HTTP crawler in Erlang

  - by ctp

  I'm coding on a simple HTTP crawler but I have an issue running the code at the bottom. I'm requesting 50 URLs and get the content of 20+ back. I've generated few files with 150kB size each to test the crawler. So I think the 20+ responses are limited by the bandwidth? BUT: how to tell the Erlang snippet not to quit until the last file is not fetched? The test data server is online, so plz try the code out and any hints are welcome :) -module(crawler). -define(BASE_URL, "http://46.4.117.69/"). -export([start/0, send_reqs/0, do_send_req/1]). start() -> ibrowse:start(), proc_lib:spawn(?MODULE, send_reqs, []). to_url(Id) -> ?BASE_URL ++ integer_to_list(Id). fetch_ids() -> lists:seq(1, 50). send_reqs() -> spawn_workers(fetch_ids()). spawn_workers(Ids) -> lists:foreach(fun do_spawn/1, Ids). do_spawn(Id) -> proc_lib:spawn_link(?MODULE, do_send_req, [Id]). do_send_req(Id) -> io:format("Requesting ID ~p ... ~n", [Id]), Result = (catch ibrowse:send_req(to_url(Id), [], get, [], [], 10000)), case Result of {ok, Status, _H, B} -> io:format("OK -- ID: ~2..0w -- Status: ~p -- Content length: ~p~n", [Id, Status, length(B)]); Err -> io:format("ERROR -- ID: ~p -- Error: ~p~n", [Id, Err]) end. That's the output: Requesting ID 1 ... Requesting ID 2 ... Requesting ID 3 ... Requesting ID 4 ... Requesting ID 5 ... Requesting ID 6 ... Requesting ID 7 ... Requesting ID 8 ... Requesting ID 9 ... Requesting ID 10 ... Requesting ID 11 ... Requesting ID 12 ... Requesting ID 13 ... Requesting ID 14 ... Requesting ID 15 ... Requesting ID 16 ... Requesting ID 17 ... Requesting ID 18 ... Requesting ID 19 ... Requesting ID 20 ... Requesting ID 21 ... Requesting ID 22 ... Requesting ID 23 ... Requesting ID 24 ... Requesting ID 25 ... Requesting ID 26 ... Requesting ID 27 ... Requesting ID 28 ... Requesting ID 29 ... Requesting ID 30 ... Requesting ID 31 ... Requesting ID 32 ... Requesting ID 33 ... Requesting ID 34 ... Requesting ID 35 ... Requesting ID 36 ... Requesting ID 37 ... Requesting ID 38 ... Requesting ID 39 ... Requesting ID 40 ... Requesting ID 41 ... Requesting ID 42 ... Requesting ID 43 ... Requesting ID 44 ... Requesting ID 45 ... Requesting ID 46 ... Requesting ID 47 ... Requesting ID 48 ... Requesting ID 49 ... Requesting ID 50 ... OK -- ID: 49 -- Status: "200" -- Content length: 150000 OK -- ID: 47 -- Status: "200" -- Content length: 150000 OK -- ID: 50 -- Status: "200" -- Content length: 150000 OK -- ID: 17 -- Status: "200" -- Content length: 150000 OK -- ID: 48 -- Status: "200" -- Content length: 150000 OK -- ID: 45 -- Status: "200" -- Content length: 150000 OK -- ID: 46 -- Status: "200" -- Content length: 150000 OK -- ID: 10 -- Status: "200" -- Content length: 150000 OK -- ID: 09 -- Status: "200" -- Content length: 150000 OK -- ID: 19 -- Status: "200" -- Content length: 150000 OK -- ID: 13 -- Status: "200" -- Content length: 150000 OK -- ID: 21 -- Status: "200" -- Content length: 150000 OK -- ID: 16 -- Status: "200" -- Content length: 150000 OK -- ID: 27 -- Status: "200" -- Content length: 150000 OK -- ID: 03 -- Status: "200" -- Content length: 150000 OK -- ID: 23 -- Status: "200" -- Content length: 150000 OK -- ID: 29 -- Status: "200" -- Content length: 150000 OK -- ID: 14 -- Status: "200" -- Content length: 150000 OK -- ID: 18 -- Status: "200" -- Content length: 150000 OK -- ID: 01 -- Status: "200" -- Content length: 150000 OK -- ID: 30 -- Status: "200" -- Content length: 150000 OK -- ID: 40 -- Status: "200" -- Content length: 150000 OK -- ID: 05 -- Status: "200" -- Content length: 150000 Update: thanks stemm for the hint with the wait_workers. I've combined your and mine code but same behaviour :( -module(crawler). -define(BASE_URL, "http://46.4.117.69/"). -export([start/0, send_reqs/0, do_send_req/2]). start() -> ibrowse:start(), proc_lib:spawn(?MODULE, send_reqs, []). to_url(Id) -> ?BASE_URL ++ integer_to_list(Id). fetch_ids() -> lists:seq(1, 50). send_reqs() -> spawn_workers(fetch_ids()). spawn_workers(Ids) -> %% collect reference to each worker Refs = [ do_spawn(Id) || Id <- Ids ], %% wait for response from each worker wait_workers(Refs). wait_workers(Refs) -> lists:foreach(fun receive_by_ref/1, Refs). receive_by_ref(Ref) -> %% receive message only from worker with specific reference receive {Ref, done} -> done end. do_spawn(Id) -> Ref = make_ref(), proc_lib:spawn_link(?MODULE, do_send_req, [Id, {self(), Ref}]), Ref. do_send_req(Id, {Pid, Ref}) -> io:format("Requesting ID ~p ... ~n", [Id]), Result = (catch ibrowse:send_req(to_url(Id), [], get, [], [], 10000)), case Result of {ok, Status, _H, B} -> io:format("OK -- ID: ~2..0w -- Status: ~p -- Content length: ~p~n", [Id, Status, length(B)]), %% send message that work is done Pid ! {Ref, done}; Err -> io:format("ERROR -- ID: ~p -- Error: ~p~n", [Id, Err]), %% repeat request if there was error while fetching a page, do_send_req(Id, {Pid, Ref}) %% or - if you don't want to repeat request, put there: %% Pid ! {Ref, done} end. Running the crawler forks fine for a handful of files, but then the code even doesnt fetch the entire files (file size each 150000 bytes) - he crawler fetches some files partially, see the following web server log :( 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /10 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /1 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /3 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /8 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /39 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /7 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /6 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /2 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /5 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /50 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /9 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /44 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /38 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /47 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /49 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /43 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /37 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /46 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /48 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /36 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /42 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /41 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /45 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /17 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /35 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /16 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /15 HTTP/1.1" 200 17020 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /21 HTTP/1.1" 200 120360 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /40 HTTP/1.1" 200 117600 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /34 HTTP/1.1" 200 60660 "-" "-" Any hints are welcome. I have no clue what's going wrong there :(

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