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• architecture python question

  - by tom smith

  hi. creating a distributed crawling python app. it consists of a master server, and associated client apps that will run on client servers. the purpose of the client app is to run across a targeted site, to extract specific data. the clients need to go "deep" within the site, behind multiple levels of forms, so each client is specifically geared towards a given site. each client app looks something like main: parse initial url call function level1 (data1) function level1 (data) parse the url, for data1 use the required xpath to get the dom elements call the next function call level2 (data) function level2 (data2) parse the url, for data2 use the required xpath to get the dom elements call the next function call level3 function level3 (dat3) parse the url, for data3 use the required xpath to get the dom elements call the next function call level4 function level4 (data) parse the url, for data4 use the required xpath to get the dom elements at the final function.. --all the data output, and eventually returned to the server --at this point the data has elements from each function... my question: given that the number of calls that is made to the child function by the current function varies, i'm trying to figure out the best approach. each function essentialy fetches a page of content, and then parses the page using a number of different XPath expressions, combined with different regex expressions depending on the site/page. if i run a client on a single box, as a sequential process, it'll take awhile, but the load on the box is rather small. i've thought of attempting to implement the child functions as threads from the current function, but that could be a nightmare, as well as quickly bring the "box" to its knees! i've thought of breaking the app up in a manner that would allow the master to essentially pass packets to the client boxes, in a way to allow each client/function to be run directly from the master. this process requires a bit of rewrite, but it has a number of advantages. a bunch of redundancy, and speed. it would detect if a section of the process was crashing and restart from that point. but not sure if it would be any faster... i'm writing the parsing scripts in python.. so... any thoughts/comments would be appreciated... i can get into a great deal more detail, but didn't want to bore anyone!! thanks! tom

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• Should Application_End fire on an automatic App Pool Recycle?

  - by Laramie

  I have read this, this, this and this plus a dozen other posts/blogs. I have an ASP.Net app in shared hosting that is frequently recycling. We use NLog and have the following code in global.asax void Application_Start(object sender, EventArgs e) { NLog.Logger logger = NLog.LogManager.GetCurrentClassLogger(); logger.Debug("\r\n\r\nAPPLICATION STARTING\r\n\r\n"); } protected void Application_OnEnd(Object sender, EventArgs e) { NLog.Logger logger = NLog.LogManager.GetCurrentClassLogger(); logger.Debug("\r\n\r\nAPPLICATION_OnEnd\r\n\r\n"); } void Application_End(object sender, EventArgs e) { HttpRuntime runtime = (HttpRuntime)typeof(System.Web.HttpRuntime).InvokeMember("_theRuntime", BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.GetField, null, null, null); if (runtime == null) return; string shutDownMessage = (string)runtime.GetType().InvokeMember("_shutDownMessage", BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.GetField, null, runtime, null); string shutDownStack = (string)runtime.GetType().InvokeMember("_shutDownStack", BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.GetField, null, runtime, null); ApplicationShutdownReason shutdownReason = System.Web.Hosting.HostingEnvironment.ShutdownReason; NLog.Logger logger = NLog.LogManager.GetCurrentClassLogger(); logger.Debug(String.Format("\r\n\r\nAPPLICATION END\r\n\r\n_shutDownReason = {2}\r\n\r\n _shutDownMessage = {0}\r\n\r\n_shutDownStack = {1}\r\n\r\n", shutDownMessage, shutDownStack, shutdownReason)); } void Application_Error(object sender, EventArgs e) { NLog.Logger logger = NLog.LogManager.GetCurrentClassLogger(); logger.Debug("\r\n\r\nApplication_Error\r\n\r\n"); } Our log file is littered with "APPLICATION STARTING" entries, but neither Application_OnEnd, Application_End, nor Application_Error are ever fired during these spontaneous restarts. I know they are working because there are entries for touching the web.config or /bin files. We also ran a memory overload test and can trigger an OutOfMemoryException which is caught in Application_Error. We are trying to determine whether the virtual memory limit is causing the recycling. We have added GC.GetTotalMemory(false) throughout the code, but this is for all of .Net, not just our App´s pool, correct? We've also tried var oPerfCounter = new PerformanceCounter(); oPerfCounter.CategoryName = "Process"; oPerfCounter.CounterName = "Virtual Bytes"; oPerfCounter.InstanceName = "iisExpress"; logger.Debug("Virtual Bytes: " + oPerfCounter.RawValue + " bytes"); but don't have permission in shared hosting. I've monitored the app on a dev server with the same requests that caused the recycles in production with ANTS Memory Profiler attached and can't seem to find a culprit. We have also run it with a debugger attached in dev to check for uncaught exceptions in spawned threads that might cause the app to abort. My questions are these: How can I effectively monitor memory usage in shared hosting to tell how much my application is consuming prior to an application recycle? Why are the Application_[End/OnEnd/Error] handlers in global.asax not being called? How else can I determine what is causing these recycles? Thanks.

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• Running same powershell script multiple asynchronous times with separate runspace

  - by teqnomad

  Hi, I have a powershell script which is called by a batch script which is called by Trap Receiver (which also passes environment variables) (running on windows 2008). The traps are flushed out at times in sets of 2-4 trap events, and the batch script will echo the trap details for each message to a logfile, but the powershell script on the next line of the batch script will only appear to process the first trap message (the powershell script writes to the same logfile). My interpetation is that the defaultrunspace is common to all iterations of the script running and this is why the others appear to be ignored. I've tried adding "-sta" when I invoke the powershell script using "powershell.exe -command", but this didn't help. I've researched and found a method using C# but I don't know this language, and busy enough learning powershell, so hoping to find a more direct solution especially as interleaving a "wrapper" between batch and powershell will involve passing the environment variables. http://www.codeproject.com/KB/threads/AsyncPowerShell.aspx I've hunted through stackoverflow, and again the only question of similar vein was using C#. Any suggestions welcome. Some script background: The powershell script is actually a modification of a great script found at gregorystrike website - cant post the link as I'm limited to one link but its the one for Lefthand arrays. Lots of mods so it can do multiple targets from one .ini file, taking in the environment variables, and options to run portions of the script interactively with winform. But you can see the gist of the original script. The batch script is pretty basic. The keys things are I'm trying to filter out trap noise using the :~ operator, and I tried -sta option to see if this would compartmentalise the powershell script. set debug=off set CMD_LINE_ARGS="%*" set LHIPAddress="%2" set VARBIND8="%8" shift shift shift shift shift shift shift set CHASSIS="%9" echo %DATE% %TIME% "Trap Received: %LHIPAddress% %CHASSIS% %VARBIND8%" >> C:\Logs\trap_out.txt set ACTION="%VARBIND8:~39,18%" echo %DATE% %TIME% "Action substring is %ACTION%" 2>&1 >> C:\Logs\trap_out.txt if %ACTION%=="Remote Copy Volume" ( echo Prepostlefthand_env_v2.9 >> C:\Logs\trap_out.txt c:\Windows\System32\WindowsPowerShell\v1.0\PowerShell.exe -sta -executionpolicy unrestricted -command " & 'C:\Scripts\prepostlefthand_env_v2.9.ps1' Backupsettings.ini ALL" 2>&1 >> C:\Logs\trap_out.txt ) ELSE ( echo %DATE% %TIME% Action substring is %ACTION% so exiting" 2>&1 >> C:\Logs\trap.out.txt ) exit

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• mysql_connect() causes page to not display (WAMP)

  - by VOIDHand

  I currently have a website running MySQL and PHP in which this is all working. I've tried installing WAMPServer to be able to work on the site on my own computer, but I have been having issues trying to get the site to work correctly. HTML and PHP files work correctly (by going to http://localhost/index.php, etc.). But some of the pages display "This Webpage is not available" (in Chrome) or "Internet Explorer cannot display this webpage", which leads me to think there is an error is the server, as when the page doesn't exist, it typically dispays "Oops! This link appears to be broken" or IE's standard 404 page. Each page in my site has an include() call to set up an instance of a class to handle all database transactions. This class opens the connection to the database in its constructor. I have found commenting out the contents of the constructor will allow the page to load, although this understandably causes errors later in the page. This is the contents of the included file: class dbAccess { private $db; function __construct() { $this->db = mysql_connect("externalURL","user","password") or die ("Connection for database not found."); mysql_select_db("dbName", $this->db) or die ("Database not selected"); } ... } As a note for what's happening here. I'm attempting to use the database on my site, rather than the local machine. The actual values of externalURL, dbName, user, and password work when I plug them into my database software and the file fine of the site, so I don't think the issue is with those values themselves, but rather some setting with Apache or Wamp. The issue persists if I try a local database as well. This is an excerpt of my Apache error log for one attempt at logging into the site: [Wed Apr 14 15:32:54 2010] [notice] Parent: child process exited with status 255 -- Restarting. [Wed Apr 14 15:32:54 2010] [notice] Apache/2.2.11 (Win32) PHP/5.3.0 configured -- resuming normal operations [Wed Apr 14 15:32:54 2010] [notice] Server built: Dec 10 2008 00:10:06 [Wed Apr 14 15:32:54 2010] [notice] Parent: Created child process 1756 [Wed Apr 14 15:32:55 2010] [notice] Child 1756: Child process is running [Wed Apr 14 15:32:55 2010] [notice] Child 1756: Acquired the start mutex. [Wed Apr 14 15:32:55 2010] [notice] Child 1756: Starting 64 worker threads. [Wed Apr 14 15:32:55 2010] [notice] Child 1756: Starting thread to listen on port 80. For the first line, isLoggedIn (from the first line) is a method of the class above. Assuming that the connection works, this error should disappear. I've tried searching for solutions online, but haven't been able to find anything to help. If you need any further information to help solve this issue, feel free to ask for it. (One more note, I don't even have Skype on this computer, so I can't see it being an issue, as this conflict seems to be the default response for any Wamp issue.) [Edit: Removed entry from the error log as it was solved as an unrelated issue]

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• Is it too early to start designing for Task Parallel Library?

  - by Joe Erickson

  I have been following the development of the .NET Task Parallel Library (TPL) with great interest since Microsoft first announced it. There is no doubt in my mind that we will eventually take advantage of TPL. What I am questioning is whether it makes sense to start taking advantage of TPL when Visual Studio 2010 and .NET 4.0 are released, or whether it makes sense to wait a while longer. Why Start Now? The .NET 4.0 Task Parallel Library appears to be well designed and some relatively simple tests demonstrate that it works well on today's multi-core CPUs. I have been very interested in the potential advantages of using multiple lightweight threads to speed up our software since buying my first quad processor Dell Poweredge 6400 about seven years ago. Experiments at that time indicated that it was not worth the effort, which I attributed largely to the overhead of moving data between each CPU's cache (there was no shared cache back then) and RAM. Competitive advantage - some of our customers can never get enough performance and there is no doubt that we can build a faster product using TPL today. It sounds fun. Yes, I realize that some developers would rather poke themselves in the eye with a sharp stick, but we really enjoy maximizing performance. Why Wait? Are today's Intel Nehalem CPUs representative of where we are going as multi-core support matures? You can purchase a Nehalem CPU with 4 cores which share a single level 3 cache today, and most likely a 6 core CPU sharing a single level 3 cache by the time Visual Studio 2010 / .NET 4.0 are released. Obviously, the number of cores will go up over time, but what about the architecture? As the number of cores goes up, will they still share a cache? One issue with Nehalem is the fact that, even though there is a very fast interconnect between the cores, they have non-uniform memory access (NUMA) which can lead to lower performance and less predictable results. Will future multi-core architectures be able to do away with NUMA? Similarly, will the .NET Task Parallel Library change as it matures, requiring modifications to code to fully take advantage of it? Limitations Our core engine is 100% C# and has to run without full trust, so we are limited to using .NET APIs.

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• Understanding VS2010 C# parallel profiling results

  - by Haggai

  I have a program with many independent computations so I decided to parallelize it. I use Parallel.For/Each. The results were okay for a dual-core machine - CPU utilization of about 80%-90% most of the time. However, with a dual Xeon machine (i.e. 8 cores) I get only about 30%-40% CPU utilization, although the program spends quite a lot of time (sometimes more than 10 seconds) on the parallel sections, and I see it employs about 20-30 more threads in those sections compared to serial sections. Each thread takes more than 1 second to complete, so I see no reason for them to work in parallel - unless there is a synchronization problem. I used the built-in profiler of VS2010, and the results are strange. Even though I use locks only in one place, the profiler reports that about 85% of the program's time is spent on synchronization (also 5-7% sleep, 5-7% execution, under 1% IO). The locked code is only a cache (a dictionary) get/add: bool esn_found; lock (lock_load_esn) esn_found = cache.TryGetValue(st, out esn); if(!esn_found) { esn = pData.esa_inv_idx.esa[term_idx]; esn.populate(pData.esa_inv_idx.datafile); lock (lock_load_esn) { if (!cache.ContainsKey(st)) cache.Add(st, esn); } } lock_load_esn is a static member of the class of type Object. esn.populate reads from a file using a separate StreamReader for each thread. However, when I press the Synchronization button to see what causes the most delay, I see that the profiler reports lines which are function entrance lines, and doesn't report the locked sections themselves. It doesn't even report the function that contains the above code (reminder - the only lock in the program) as part of the blocking profile with noise level 2%. With noise level at 0% it reports all the functions of the program, which I don't understand why they count as blocking synchronizations. So my question is - what is going on here? How can it be that 85% of the time is spent on synchronization? How do I find out what really is the problem with the parallel sections of my program? Thanks.

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• State machines in C#

  - by Sir Psycho

  Hi, I'm trying to work out what's going on with this code. I have two threads iterating over the range and I'm trying to understand what is happening when the second thread calls GetEnumerator(). This line in particular (T current = start;), seems to spawn a new 'instance' in this method by the second thread. Seeing that there is only one instance of the DateRange class, I'm trying to understand why this works. Thanks in advance. class Program { static void Main(string[] args) { var daterange = new DateRange(DateTime.Now, DateTime.Now.AddDays(10), new TimeSpan(24, 0, 0)); var ts1 = new ThreadStart(delegate { foreach (var date in daterange) { Console.WriteLine("Thread " + Thread.CurrentThread.ManagedThreadId + " " + date); } }); var ts2 = new ThreadStart(delegate { foreach (var date in daterange) { Console.WriteLine("Thread " + Thread.CurrentThread.ManagedThreadId + " " + date); } }); Thread t1 = new Thread(ts1); Thread t2 = new Thread(ts2); t1.Start(); Thread.Sleep(4000); t2.Start(); Console.Read(); } } public class DateRange : Range<DateTime> { public DateTime Start { get; private set; } public DateTime End { get; private set; } public TimeSpan SkipValue { get; private set; } public DateRange(DateTime start, DateTime end, TimeSpan skip) : base(start, end) { SkipValue = skip; } public override DateTime GetNextElement(DateTime current) { return current.Add(SkipValue); } } public abstract class Range<T> : IEnumerable<T> where T : IComparable<T> { readonly T start; readonly T end; public Range(T start, T end) { if (start.CompareTo(end) > 0) throw new ArgumentException("Start value greater than end value"); this.start = start; this.end = end; } public abstract T GetNextElement(T currentElement); public IEnumerator<T> GetEnumerator() { T current = start; do { Thread.Sleep(1000); yield return current; current = GetNextElement(current); } while (current.CompareTo(end) < 1); } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return GetEnumerator(); } }

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• Arguments for moving from LINQtoSQL to Nhibernate?

  - by sah302

  Backstory: Hi all, I just spent a lot of time reading many of the LINQ vs Nhibernate threads here and on other sites. I work in a small development team of 4 people and we don't even have really any super experienced developers. We work for a small company that has a lot of technical needs but not enough developers to implement them (and hiring more is out of the question right now). Typically our projects (which individually are fairly small) have been coded separately and weren't really layered in anyway, code wasn't re-used, no class libraries, and we just use the LINQtoSQL .dbml files for our pojects, we really don't even use objects but pass around values and stuff, the only time we use objects is when inserting to a database (heck not even querying since you don't need to assign it to a type and can just bind to gridview). Despite all this as I said our company has a lot of technical needs, no one could come to us for a year and we would have plenty of work to implement requested features. Well I have decided to change that a bit first by creating class libraries and actually adding layers to our applications. I am trying to meet these guys halfway by still using LINQtoSQL as the ORM yet and still use VB as the language. However I am finding it a b***h of a time dealing with so many thing in LINQtoSQL that I found easy in Nhibernate (automatic handling of the session, criteria creation easier than expression trees, generic an dynamic querying easier etc.) So... Question: How can I convince my lead developers and other senior programmers that switching to Nhibernate is a good thing? That being in control of our domain objects is a good thing? That being able to implement interfaces is a good? I've tried exlpaining the advantages of this before but it's not understood by them because they've never programmed in a true OO & layered way. Also one of the counter arguments to this I can see is sqlMetal generates those classes automatically and therefore it saves a lot of time. I can't really counter that other than saying spending more time on infrastructure to make it more scalable and flexible is good, but they can't see how. Again, I know the features and advantages (somewhat enough I believe) of each, but I need arguments applicable to my context, hence why I provided the context. I just am not a very good arguer I guess. (Caveat: For all the LINQtoSQL lovers, I may just not be super proficient as LINQ, but I find it very cumbersome that you are required to download some extra library for dynamic queries which don't by default support guid comparisons, and I also find the way of updating entitites to be cumbersome as well in terms of data context managing, so it could just be that I suck hehe.)

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• Accidental Complexity in OpenSSL HMAC functions

  - by Hassan Syed

  SSL Documentation Analaysis This question is pertaining the usage of the HMAC routines in OpenSSL. Since Openssl documentation is a tad on the weak side in certain areas, profiling has revealed that using the: unsigned char *HMAC(const EVP_MD *evp_md, const void *key, int key_len, const unsigned char *d, int n, unsigned char *md, unsigned int *md_len); From here, shows 40% of my library runtime is devoted to creating and taking down **HMAC_CTX's behind the scenes. There are also two additional function to create and destroy a HMAC_CTX explicetly: HMAC_CTX_init() initialises a HMAC_CTX before first use. It must be called. HMAC_CTX_cleanup() erases the key and other data from the HMAC_CTX and releases any associated resources. It must be called when an HMAC_CTX is no longer required. These two function calls are prefixed with: The following functions may be used if the message is not completely stored in memory My data fits entirely in memory, so I choose the HMAC function -- the one whose signature is shown above. The context, as described by the man page, is made use of by using the following two functions: HMAC_Update() can be called repeatedly with chunks of the message to be authenticated (len bytes at data). HMAC_Final() places the message authentication code in md, which must have space for the hash function output. The Scope of the Application My application generates a authentic (HMAC, which is also used a nonce), CBC-BF encrypted protocol buffer string. The code will be interfaced with various web-servers and frameworks Windows / Linux as OS, nginx, Apache and IIS as webservers and Python / .NET and C++ web-server filters. The description above should clarify that the library needs to be thread safe, and potentially have resumeable processing state -- i.e., lightweight threads sharing a OS thread (which might leave thread local memory out of the picture). The Question How do I get rid of the 40% overhead on each invocation in a (1) thread-safe / (2) resume-able state way ? (2) is optional since I have all of the source-data present in one go, and can make sure a digest is created in place without relinquishing control of the thread mid-digest-creation. So, (1) can probably be done using thread local memory -- but how do I resuse the CTX's ? does the HMAC_final() call make the CTX reusable ?. (2) optional: in this case I would have to create a pool of CTX's. (3) how does the HMAC function do this ? does it create a CTX in the scope of the function call and destroy it ? Psuedocode and commentary will be useful.

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• COMException Problem

  - by Jack Harvin

  Wondering if anyone could help with my problem. Below is the code, and after the code an explination of where the exception is thrown. using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.Web; using WatiN.Core; using System.Threading; using System.IO; namespace WindowsFormsApplication1 { public partial class Form1 : System.Windows.Forms.Form { public Form1() { InitializeComponent(); } private void Form1_Load(object sender, EventArgs e) { } private void button1_Click(object sender, EventArgs e) { Thread t = new Thread(createApplications); Settings.AutoStartDialogWatcher = false; t.SetApartmentState(System.Threading.ApartmentState.STA); t.Start(); } private void createApplications() { createApp("username", "password", "Test App", "This is just a test description", "http:/mysite.com"); } private void createApp(String username, String password, String appName, String description, String appUrl) { var currentBrowser = new IE("http://mysite.com/login/php"); currentBrowser.TextField(Find.ById("username")).TypeText(username); currentBrowser.TextField(Find.ById("password")).TypeText(password); currentBrowser.Button(Find.ById("submit")).Click(); currentBrowser.GoTo("http://mysite.com/createmusicapp.php"); currentBrowser.TextField(Find.ById("application_name")).TypeText(appName); currentBrowser.TextField(Find.ById("application_description")).TypeText(description); currentBrowser.TextField(Find.ById("application_url")).TypeText(appUrl); currentBrowser.RadioButton(Find.ById("client_application_desktop_1")).Click(); currentBrowser.RadioButton(Find.ById("client_application_is_writable_1")).Click(); WatiN.Core.Image captchaImage = currentBrowser.Div(Find.ById("recaptcha_image")).Image(Find.ByStyle("display", "block")); Form2 captcha = new Form2(captchaImage.Src); captcha.ShowDialog(); } } } The exception is thrown on this line: currentBrowser.TextField(Find.ById("username")).TypeText(username); BUT, it's thrown when it gets to this line: captcha.ShowDialog(); It logs in, and fills in the app details and Form2 loads fine, but once loaded, after around 2-3 seconds the exception happens. I am wondering if it's anything to do with the threads? But I wouldn't know how to solve it if it was. The complete exception thrown is: The object invoked has disconnected from its clients. (Exception from HRESULT: 0x80010108 (RPC_E_DISCONNECTED))

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• JBOSS 7 encoding not working as expected

  - by Fofole

  I had problems with my listgrids not showing diacritcs corectly and I found out that when I inserted from java into the db the values where already bugged. A post here helped and I changed my project properties - Text encoding - other - UTF-8 and this fixed my problem. Thing is this only fixes my problem locally. What I need to do is on my Jboss server also set the encoding somehow. This is what I put in my configuration file: <?xml version='1.0' encoding='UTF-8'?> <server name="vali-ubuntu" xmlns="urn:jboss:domain:1.0"> extensions> extension module="org.jboss.as.clustering.infinispan"/> extension module="org.jboss.as.connector"/> extension module="org.jboss.as.deployment-scanner"/> extension module="org.jboss.as.ee"/> extension module="org.jboss.as.ejb3"/> extension module="org.jboss.as.jaxrs"/> extension module="org.jboss.as.jmx"/> extension module="org.jboss.as.logging"/> extension module="org.jboss.as.naming"/> extension module="org.jboss.as.osgi"/> extension module="org.jboss.as.remoting"/> extension module="org.jboss.as.sar"/> extension module="org.jboss.as.security"/> extension module="org.jboss.as.threads"/> extension module="org.jboss.as.transactions"/> extension module="org.jboss.as.web"/> extension module="org.jboss.as.weld"/> /extensions> system-properties> property name="org.apache.catalina.connector.URI_ENCODING" value="UTF-8"/> property name="org.apache.catalina.connector.USE_BODY_ENCODING_FOR_QUERY_STRING" value="tru e"/> /system-properties> //..... This doesn't work so maybe I need to add something else. I tried everything I could find with no succes so any help is appreciated. Thanks. EDIT:From what I read, this will work only in jboss 7.1.0 beta 1 or highier. (URIEncoding) and I use JBoss 7.0.2 so I need a replacement for 7.0.2

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• Python multiprocessing global variable updates not returned to parent

  - by user1459256

  I am trying to return values from subprocesses but these values are unfortunately unpicklable. So I used global variables in threads module with success but have not been able to retrieve updates done in subprocesses when using multiprocessing module. I hope I'm missing something. The results printed at the end are always the same as initial values given the vars dataDV03 and dataDV04. The subprocesses are updating these global variables but these global variables remain unchanged in the parent. import multiprocessing # NOT ABLE to get python to return values in passed variables. ants = ['DV03', 'DV04'] dataDV03 = ['', ''] dataDV04 = {'driver': '', 'status': ''} def getDV03CclDrivers(lib): # call global variable global dataDV03 dataDV03[1] = 1 dataDV03[0] = 0 # eval( 'CCL.' + lib + '.' + lib + '( "DV03" )' ) these are unpicklable instantiations def getDV04CclDrivers(lib, dataDV04): # pass global variable dataDV04['driver'] = 0 # eval( 'CCL.' + lib + '.' + lib + '( "DV04" )' ) if __name__ == "__main__": jobs = [] if 'DV03' in ants: j = multiprocessing.Process(target=getDV03CclDrivers, args=('LORR',)) jobs.append(j) if 'DV04' in ants: j = multiprocessing.Process(target=getDV04CclDrivers, args=('LORR', dataDV04)) jobs.append(j) for j in jobs: j.start() for j in jobs: j.join() print 'Results:\n' print 'DV03', dataDV03 print 'DV04', dataDV04 I cannot post to my question so will try to edit the original. Here is the object that is not picklable: In [1]: from CCL import LORR In [2]: lorr=LORR.LORR('DV20', None) In [3]: lorr Out[3]: <CCL.LORR.LORR instance at 0x94b188c> This is the error returned when I use a multiprocessing.Pool to return the instance back to the parent: Thread getCcl (('DV20', 'LORR'),) Process PoolWorker-1: Traceback (most recent call last): File "/alma/ACS-10.1/casa/lib/python2.6/multiprocessing/process.py", line 232, in _bootstrap self.run() File "/alma/ACS-10.1/casa/lib/python2.6/multiprocessing/process.py", line 88, in run self._target(*self._args, **self._kwargs) File "/alma/ACS-10.1/casa/lib/python2.6/multiprocessing/pool.py", line 71, in worker put((job, i, result)) File "/alma/ACS-10.1/casa/lib/python2.6/multiprocessing/queues.py", line 366, in put return send(obj) UnpickleableError: Cannot pickle <type 'thread.lock'> objects In [5]: dir(lorr) Out[5]: ['GET_AMBIENT_TEMPERATURE', 'GET_CAN_ERROR', 'GET_CAN_ERROR_COUNT', 'GET_CHANNEL_NUMBER', 'GET_COUNT_PER_C_OP', 'GET_COUNT_REMAINING_OP', 'GET_DCM_LOCKED', 'GET_EFC_125_MHZ', 'GET_EFC_COMB_LINE_PLL', 'GET_ERROR_CODE_LAST_CAN_ERROR', 'GET_INTERNAL_SLAVE_ERROR_CODE', 'GET_MAGNITUDE_CELSIUS_OP', 'GET_MAJOR_REV_LEVEL', 'GET_MINOR_REV_LEVEL', 'GET_MODULE_CODES_CDAY', 'GET_MODULE_CODES_CMONTH', 'GET_MODULE_CODES_DIG1', 'GET_MODULE_CODES_DIG2', 'GET_MODULE_CODES_DIG4', 'GET_MODULE_CODES_DIG6', 'GET_MODULE_CODES_SERIAL', 'GET_MODULE_CODES_VERSION_MAJOR', 'GET_MODULE_CODES_VERSION_MINOR', 'GET_MODULE_CODES_YEAR', 'GET_NODE_ADDRESS', 'GET_OPTICAL_POWER_OFF', 'GET_OUTPUT_125MHZ_LOCKED', 'GET_OUTPUT_2GHZ_LOCKED', 'GET_PATCH_LEVEL', 'GET_POWER_SUPPLY_12V_NOT_OK', 'GET_POWER_SUPPLY_15V_NOT_OK', 'GET_PROTOCOL_MAJOR_REV_LEVEL', 'GET_PROTOCOL_MINOR_REV_LEVEL', 'GET_PROTOCOL_PATCH_LEVEL', 'GET_PROTOCOL_REV_LEVEL', 'GET_PWR_125_MHZ', 'GET_PWR_25_MHZ', 'GET_PWR_2_GHZ', 'GET_READ_MODULE_CODES', 'GET_RX_OPT_PWR', 'GET_SERIAL_NUMBER', 'GET_SIGN_OP', 'GET_STATUS', 'GET_SW_REV_LEVEL', 'GET_TE_LENGTH', 'GET_TE_LONG_FLAG_SET', 'GET_TE_OFFSET_COUNTER', 'GET_TE_SHORT_FLAG_SET', 'GET_TRANS_NUM', 'GET_VDC_12', 'GET_VDC_15', 'GET_VDC_7', 'GET_VDC_MINUS_7', 'SET_CLEAR_FLAGS', 'SET_FPGA_LOGIC_RESET', 'SET_RESET_AMBSI', 'SET_RESET_DEVICE', 'SET_RESYNC_TE', 'STATUS', '_HardwareDevice__componentName', '_HardwareDevice__hw', '_HardwareDevice__stickyFlag', '_LORRBase__logger', '__del__', '__doc__', '__init__', '__module__', '_devices', 'clearDeviceCommunicationErrorAlarm', 'getControlList', 'getDeviceCommunicationErrorCounter', 'getErrorMessage', 'getHwState', 'getInternalSlaveCanErrorMsg', 'getLastCanErrorMsg', 'getMonitorList', 'hwConfigure', 'hwDiagnostic', 'hwInitialize', 'hwOperational', 'hwSimulation', 'hwStart', 'hwStop', 'inErrorState', 'isMonitoring', 'isSimulated'] In [6]:

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• feeling insufficient while looking for a programming job ...

  - by user325661

  Hello everybody It's really dream to be programmer for me.So i always wanted to be .I had so small knowledges from commodore basic which i couldn't figure out anything in it .Then i tried to learn Visual basic 6 by myself and result wasn't good as i expected because i even didn't understand classes.Then i left to learning programming and to dream to be programmer. But challenge hadn't finished yet . After all of these i started to learn c# and i did chess engine which i hadn't believe that i can create one.I sometimes feel that i understand many thing about programming like knowing classes ,inheritance,abstract class and methods why exist , interfaces ,extension methods ,static classes ,threads. but i am not expert all in it . i just know that as i need . i don't know still i will learn many thing about these.i have also learned html, css2 , php and database concepts a little sql ,tables relations between primary keys etc but i haven't used them in praticaly . i just did some samples so i feel i am lack of knowledges. As a result still i can't evaluate my skills and can't decide what is my level.I just feel myself one step ahead of junior sometimes :) . Still can't decide that it is time to job seeking. While searching job on web i have never seen a junior advertisement. All looking for a good experiencing one.Nobody care about juniors. When found job advertisement which i feel sufficient myself a little then i start to feel that i think i can't do what they want from me and loosing job after have it in short time would leave many crap feelings into my low self-confidence. Please advise me something ... Also i want to ask some of concentrate questions. 1) If i enter a job which i can't provide their expectations should be in employers responsibility to test me while apply the job ? 2) If i answer "yes , i can " questions which is abstract(for example: can u do something like this) would be my responsibility ? Because such abstract questions is not clear and can't know before start it what i really can or not . 3) i have no professional experiences in this job so i even don't know how teams working on projects but a friend of me said that programmers only write method bodies while seniors create all project.So it looks what i can do really easy but i feel that small companies doesn't work like this so it is better work in a big company for starting who has seniors? 4)last applied job was looking for c# . net developer but then i learn that they need .net web developer.Does it take long time to learn specific sides of web programming while knowing c# desktop programming ? Thanks for all answers since now.

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• Calling 32 bit unmanaged dlls from C# randomly failing

  - by Bert

  Hi, I'm having an issue when calling 32 bit delphi dll's from c# web site. The code generally runs fine, but occasionally I get an error Unable to load DLL '': The specified module could not be found. (Exception from HRESULT: 0x8007007E). This issue persists until I recycle the app pool for the site, and then it works fine again. On the same server, there is also a web service that is calling the same set of dlls. This web service doesn't seem to have the same issue that the web site has. Both applications are using .net framework 3.5, separate app pools on IIS. Here is the code I'm using to wrap the dlls: public sealed class Mapper { static Mapper instance = null; [DllImport("kernel32.dll")] private static extern bool SetDllDirectory(string lpPathName); private Mapper() { SetDllDirectory(ConfigManager.Path); } public static Mapper Instance { get { if (instance == null) { instance = new Mapper(); } return instance; } } public int Foo(string bar, ref double val) { return Loader.Foo(bar, ref val); } } public static class Loader { [DllImport("some.dll", CallingConvention = CallingConvention.StdCall, CharSet = CharSet.Unicode, EntryPoint = "foo")] public static extern int Foo(string bar, ref double val); } Then I call it like this: double val = 0.0; Mapper.Instance.Foo("bar", ref val); Any ideas as to why it would "randomly" Unable to load DLL '': The specified module could not be found. (Exception from HRESULT: 0x8007007E). The other problem is that I haven't been able to replicate the issue in the development environment. I thought that due to 2 applications calling the same dlls, that there could be some locks occurring. To replicate this, I created an app that spawned multiple threads and repeatedly called the 32bit dlls, and then used the web site to call these same dlls. I still couldn't replicate the issue. Some possible fixes that I can think of: Wrap the 32 bit dlls in web service (because the webservice doesn't seem to suffer from the same problem). But this may be worthless if it turns out that the web service also fails. Set up state server for the session state and periodically recycle the app pool for the site.This isn't fixing the problem, only avoiding it. Wrap the dll's in exe, and call that exe. Then I shouldn't get the same issue. But this also seems like a hacky solution. Implement the mapper class differently ? But how else should I be doing the call? The other draw back is that other applications are using this mapper, so I'd need to change there code too. Thanks

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• Unlocking a mutex from a different thread (C++)

  - by dan

  I'm using the C++ boost::thread library, which in my case means I'm using pthreads. Officially, a mutex must be unlocked from the same thread which locks it, and I want the effect of being able to lock in one thread and then unlock in another. There are many ways to accomplish this. One possibility would be to write a new mutex class which allows this behavior. For example: class inter_thread_mutex{ bool locked; boost::mutex mx; boost::condition_variable cv; public: void lock(){ boost::unique_lock<boost::mutex> lck(mx); while(locked) cv.wait(lck); locked=true; } void unlock(){ { boost::lock_guard<boost::mutex> lck(mx); if(!locked) error(); locked=false; } cv.notify_one(); } // bool try_lock(); void error(); etc. } I should point out that the above code doesn't guarantee FIFO access, since if one thread calls lock() while another calls unlock(), this first thread may acquire the lock ahead of other threads which are waiting. (Come to think of it, the boost::thread documentation doesn't appear to make any explicit scheduling guarantees for either mutexes or condition variables). But let's just ignore that (and any other bugs) for now. My question is, if I decide to go this route, would I be able to use such a mutex as a model for the boost Lockable concept. For example, would anything go wrong if I use a boost::unique_lock< inter_thread_mutex for RAII-style access, and then pass this lock to boost::condition_variable_any.wait(), etc. On one hand I don't see why not. On the other hand, "I don't see why not" is usually a very bad way of determining whether something will work. The reason I ask is that if it turns out that I have to write wrapper classes for RAII locks and condition variables and whatever else, then I'd rather just find some other way to achieve the same effect.

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• AlarmManager triggers PendingIntent too soon

  - by Wezelkrozum

  I've searched for 3 days now but didn't find a solution or similar problem/question anywhere else. Here is the deal: Trigger in 1 hour - works correct Trigger in 2 hours - Goes of in 1:23 Trigger in 1 day - Goes of in ~11:00 So why is the AlarmManager so unpredictable and always too soon? Or what am I doing wrong? And is there another way so that it could work correctly? This is the way I register my PendingIntent in the AlarmManager (stripped down): AlarmManager alarmManager = (AlarmManager)parent.getSystemService(ALARM_SERVICE); Intent myIntent = new Intent(parent, UpdateKlasRoostersService.class); PendingIntent pendingIntent = PendingIntent.getService(parent, 0, myIntent, PendingIntent.FLAG_UPDATE_CURRENT); //Set startdate of PendingIntent so it triggers in 10 minutes Calendar start = Calendar.getInstance(); start.setTimeInMillis(SystemClock.elapsedRealtime()); start.add(Calendar.MINUTE, 10); //Set interval of PendingIntent so it triggers every day Integer interval = 1*24*60*60*1000; //Cancel any similar instances of this PendingIntent if already scheduled alarmManager.cancel(pendingIntent); //Schedule PendingIntent alarmManager.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP, start.getTimeInMillis(), interval, pendingIntent); //Old way I used to schedule a PendingIntent, didn't seem to work either //alarmManager.set(AlarmManager.RTC_WAKEUP, start.getTimeInMillis(), pendingIntent); It would be awesome if anyone has a solution. Thanks for any help! Update: 2 hours ago it worked to trigger it with an interval of 2 hours, but after that it triggered after 1:20 hours. It's getting really weird. I'll track the triggers down with a logfile and post it here tomorrow. Update: The PendingIntent is scheduled to run every 3 hours. From the log's second line it seems like an old scheduled PendingIntent is still running: [2012-5-3 2:15:42 519] Updating Klasroosters [2012-5-3 4:15:15 562] Updating Klasroosters [2012-5-3 5:15:42 749] Updating Klasroosters [2012-5-3 8:15:42 754] Updating Klasroosters [2012-5-3 11:15:42 522] Updating Klasroosters But, I'm sure I cancelled the scheduled PendingIntent's before I schedule a new one. And every PendingIntent isn't recreated in the same way, so it should be exactly the same. If not , this threads question isn't relevant anymore.

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• JPanel components paint-time problem

  - by Tom Brito

  I'm having a problem that when my frame is shown (after a login dialog) the buttons are not on correct position, then in some miliseconds they go to the right position (the center of the panel with border layout). When I make a SSCCE, it works correct, but when I run my whole code I have this fast-miliseconds delay to the buttons to go to the correct place. Unfortunately, I can't post the whole code, but the method that shows the frame is: public void login(JComponent userView) { centerPanel.removeAll(); centerPanel.add(userView); centerPanel.revalidate(); centerPanel.repaint(); frame.setVisible(true); } What would cause this delay to the panel layout? (I'm running everything in the EDT) -- update In my machine, this SSCCE shows the layout problem in 2 of 10 times I run it: import java.awt.BorderLayout; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.SwingUtilities; public class TEST { public static void main(String[] args) throws Exception { SwingUtilities.invokeAndWait(new Runnable() { @Override public void run() { System.out.println("Debug test..."); JPanel btnPnl = new JPanel(); btnPnl.add(new JButton("TEST")); JFrame f = new JFrame("TEST"); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); f.getContentPane().setLayout(new BorderLayout()); f.getContentPane().add(btnPnl); f.pack(); f.setSize(800, 600); f.setVisible(true); System.out.println("End debug test!"); } }); } } The button first appers in the up-left, and then it goes to the center. Please, note that I'm understand, not just correct. Is it a java bug? --update OK, so the SSCCE don't show the problem with you that tried till now. Maybe it's my computer performance problem. But this don't answer the question, I still think Java Swing is creating new threads for make the layout behind the scenes.

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• Issues with LINQ (to Entity) [adding records]

  - by Mario

  I am using LINQ to Entity in a project, where I pull a bunch of data (from the database) and organize it into a bunch of objects and save those to the database. I have not had problems writing to the db before using LINQ to Entity, but I have run into a snag with this particular one. Here's the error I get (this is the "InnerException", the exception itself is useless!): New transaction is not allowed because there are other threads running in the session. I have seen that before, when I was trying to save my changes inside a loop. In this case, the loop finishes, and it tries to make that call, only to give me the exception. Here's the current code: try { //finalResult is a list of the keys to match on for the records being pulled foreach (int i in finalResult) { var queryEff = (from eff in dbMRI.MemberEligibility where eff.Member_Key == i && eff.EffDate >= DateTime.Now select eff.EffDate).Min(); if (queryEff != null) { //Add a record to the Process table Process prRecord = new Process(); prRecord.GroupData = qa; prRecord.Member_Key = i; prRecord.ProcessDate = DateTime.Now; prRecord.RecordType = "F"; prRecord.UsernameMarkedBy = "Autocard"; prRecord.GroupsId = qa.GroupsID; prRecord.Quantity = 2; prRecord.EffectiveDate = queryEff; dbMRI.AddObject("Process", prRecord); } } dbMRI.SaveChanges(); //<-- Crashes here foreach (int i in finalResult) { var queryProc = from pro in dbMRI.Process where pro.Member_Key == i && pro.UsernameMarkedBy == "Autocard" select pro; foreach (var qp in queryProc) { Audit aud = new Audit(); aud.Member_Key = i; aud.ProcessId = qp.ProcessId; aud.MarkDate = DateTime.Now; aud.MarkedByUsername = "Autocard"; aud.GroupData = qa; dbMRI.AddObject("Audit", aud); } } dbMRI.SaveChanges(); //<-- AND here (if the first one is commented out) } catch (Exception e) { //Do Something here } Basically, I need it to insert a record, get the identity for that inserted record and insert a record into another table with the identity from the first record. Given some other constraints, it is not possible to create a FK relationship between the two (I've tried, but some other parts of the app won't allow it, AND my DBA team for whatever reason hates FK's, but that's for a different topic :)) Any ideas what might be causing this? Thank!

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• java concurrency: many writers, one reader

  - by Janning

  I need to gather some statistics in my software and i am trying to make it fast and correct, which is not easy (for me!) first my code so far with two classes, a StatsService and a StatsHarvester public class StatsService { private Map<String, Long> stats = new HashMap<String, Long>(1000); public void notify ( String key ) { Long value = 1l; synchronized (stats) { if (stats.containsKey(key)) { value = stats.get(key) + 1; } stats.put(key, value); } } public Map<String, Long> getStats ( ) { Map<String, Long> copy; synchronized (stats) { copy = new HashMap<String, Long>(stats); stats.clear(); } return copy; } } this is my second class, a harvester which collects the stats from time to time and writes them to a database. public class StatsHarvester implements Runnable { private StatsService statsService; private Thread t; public void init ( ) { t = new Thread(this); t.start(); } public synchronized void run ( ) { while (true) { try { wait(5 * 60 * 1000); // 5 minutes collectAndSave(); } catch (InterruptedException e) { e.printStackTrace(); } } } private void collectAndSave ( ) { Map<String, Long> stats = statsService.getStats(); // do something like: // saveRecords(stats); } } At runtime it will have about 30 concurrent running threads each calling notify(key) about 100 times. Only one StatsHarvester is calling statsService.getStats() So i have many writers and only one reader. it would be nice to have accurate stats but i don't care if some records are lost on high concurrency. The reader should run every 5 Minutes or whatever is reasonable. Writing should be as fast as possible. Reading should be fast but if it locks for about 300ms every 5 minutes, its fine. I've read many docs (Java concurrency in practice, effective java and so on), but i have the strong feeling that i need your advice to get it right. I hope i stated my problem clear and short enough to get valuable help.

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• java.util.zip - ZipInputStream v.s. ZipFile

  - by lucho

  Hello, community! I have some general questions regarding the java.util.zip library. What we basically do is an import and an export of many small components. Previously these components were imported and exported using a single big file, e.g.: <component-type-a id="1"/> <component-type-a id="2"/> <component-type-a id="N"/> <component-type-b id="1"/> <component-type-b id="2"/> <component-type-b id="N"/> Please note that the order of the components during import is relevant. Now every component should occupy its own file which should be externally versioned, QA-ed, bla, bla. We decided that the output of our export should be a zip file (with all these files in) and the input of our import should be a similar zip file. We do not want to explode the zip in our system. We do not want opening separate streams for each of the small files. My current questions: Q1. May the ZipInputStream guarantee that the zip entries (the little files) will be read in the same order in which they were inserted by our export that uses ZipOutputStream? I assume reading is something like: ZipInputStream zis = new ZipInputStream(new BufferedInputStream(fis)); ZipEntry entry; while((entry = zis.getNextEntry()) != null) { //read from zis until available } I know that the central zip directory is put at the end of the zip file but nevertheless the file entries inside have sequential order. I also know that relying on the order is an ugly idea but I just want to have all the facts in mind. Q2. If I use ZipFile (which I prefer) what is the performance impact of calling getInputStream() hundreds of times? Will it be much slower than the ZipInputStream solution? The zip is opened only once and ZipFile is backed by RandomAccessFile - is this correct? I assume reading is something like: ZipFile zipfile = new ZipFile(argv[0]); Enumeration e = zipfile.entries();//TODO: assure the order of the entries while(e.hasMoreElements()) { entry = (ZipEntry) e.nextElement(); is = zipfile.getInputStream(entry)); } Q3. Are the input streams retrieved from the same ZipFile thread safe (e.g. may I read different entries in different threads simultaneously)? Any performance penalties? Thanks for your answers!

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• Flash Buttons Don't Work: TypeError: Error #1009: Cannot access a property or method of a null objec

  - by goldenfeelings

  I've read through several threads about this error, but haven't been able to apply it to figure out my situation... My flash file is an approx 5 second animation. Then, the last keyframe of each layer (frame #133) has a button in it. My flash file should stop on this last key frame, and you should be able to click on any of the 6 buttons to navigate to another html page in my website. Here is the Action Script that I have applied to the frame in which the buttons exist (on a separate layer, see screenshot at: http://www.footprintsfamilyphoto.com/wp-content/themes/Footprints/images/flash_buttonissue.jpg stop (); function babieschildren(event:MouseEvent):void { trace("babies children method was called!!!"); var targetURL:URLRequest = new URLRequest("http://www.footprintsfamilyphoto.com/portfolio/babies-children"); navigateToURL(targetURL, "_self"); } bc_btn1.addEventListener(MouseEvent.CLICK, babieschildren); bc_btn2.addEventListener(MouseEvent.CLICK, babieschildren); function fams(event:MouseEvent):void { trace("families method was called!!!"); var targetURL:URLRequest = new URLRequest("http://www.footprintsfamilyphoto.com/portfolio/families"); navigateToURL(targetURL, "_self"); } f_btn1.addEventListener(MouseEvent.CLICK, fams); f_btn2.addEventListener(MouseEvent.CLICK, fams); function couplesweddings(event:MouseEvent):void { trace("couples weddings method was called!!!"); var targetURL:URLRequest = new URLRequest("http://www.footprintsfamilyphoto.com/portfolio/couples-weddings"); navigateToURL(targetURL, "_self"); } cw_btn1.addEventListener(MouseEvent.CLICK, couplesweddings); cw_btn2.addEventListener(MouseEvent.CLICK, couplesweddings); When I test the movie, I get this error in the output box: "TypeError: Error #1009: Cannot access a property or method of a null object reference." The test movie does stop on the appropriate frame, but the buttons don't do anything (no URL is opened, and the trace statements don't show up in the output box when the buttons are clicked on the test movie). You can view the .swf file here: www.footprintsfamilyphoto.com/portfolio I'm confident that all 6 buttons do exist in the appropriate frame (frame 133), so I don't think that's what's causing the 1009 error. I also tried deleting each of the three function/addEventListener sections one at a time and testing, and I still got the 1009 error every time. If I delete ALL of the action script except for the "stop ()" line, then I do NOT get the 1009 error. Any ideas?? I'm very new to Flash, so if I haven't clarified something that I need to, let me know!

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• How do you prevent IDisposable from spreading to all your classes?

  - by GrahamS

  Start with these simple classes... Let's say I have a simple set of classes like this: class Bus { Driver busDriver = new Driver(); } class Driver { Shoe[] shoes = { new Shoe(), new Shoe() }; } class Shoe { Shoelace lace = new Shoelace(); } class Shoelace { bool tied = false; } A Bus has a Driver, the Driver has two Shoes, each Shoe has a Shoelace. All very silly. Add an IDisposable object to Shoelace Later I decide that some operation on the Shoelace could be multi-threaded, so I add an EventWaitHandle for the threads to communicate with. So Shoelace now looks like this: class Shoelace { private AutoResetEvent waitHandle = new AutoResetEvent(false); bool tied = false; // ... other stuff .. } Implement IDisposable on Shoelace Buit now FxCop will complain: "Implement IDisposable on 'Shoelace' because it creates members of the following IDisposable types: 'EventWaitHandle'." Okay, I implement IDisposable on Shoelace and my neat little class becomes this horrible mess: class Shoelace : IDisposable { private AutoResetEvent waitHandle = new AutoResetEvent(false); bool tied = false; private bool disposed = false; public void Dispose() { Dispose(true); GC.SuppressFinalize(this); } ~Shoelace() { Dispose(false); } protected virtual void Dispose(bool disposing) { if (!this.disposed) { if (disposing) { if (waitHandle != null) { waitHandle.Close(); waitHandle = null; } } // No unmanaged resources to release otherwise they'd go here. } disposed = true; } } Or (as pointed out by commenters) since Shoelace itself has no unmanaged resources, I might use the simpler dispose implementation without needing the Dispose(bool) and Destructor: class Shoelace : IDisposable { private AutoResetEvent waitHandle = new AutoResetEvent(false); bool tied = false; public void Dispose() { if (waitHandle != null) { waitHandle.Close(); waitHandle = null; } GC.SuppressFinalize(this); } } Watch in horror as IDisposable spreads Right that's that fixed. But now FxCop will complain that Shoe creates a Shoelace, so Shoe must be IDisposable too. And Driver creates Shoe so Driver must be IDisposable. and Bus creates Driver so Bus must be IDisposable and so on. Suddenly my small change to Shoelace is causing me a lot of work and my boss is wondering why I need to checkout Bus to make a change to Shoelace. The Question How do you prevent this spread of IDisposable, but still ensure that your unmanaged objects are properly disposed?

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• JAVA - Strange problem (probably thread problem) with JTable & Model

  - by Stefanos Kargas

  I am using 2 Tables (JTable) with their DefaultTableModels. The first table is already populated. The second table is populated for each row of the first table (using an SQL Query). My purpose is to export every line of the first table with it's respective lines of the second in an Excel File. I am doing it with a for (for each line of 1st table), in which I write a line of the 1st table in the Excel File, then I populate the 2nd table (for this line of 1st Table), I get every line from the Table (from it's Model actually) and put it in the Excel File under the current line of 1st table. This means that if I have n lines in first table I will clear and populate again the second table n times. All this code is called in a seperate thread. THE PROBLEM IS: Everything works perfectly fine ecxept that I am getting some exceptions. The strange thing is that I'm not getting anything false in my result. The Excel file is perfect. Some of the lines of the exceptions are: Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: 0 = 0 at java.util.Vector.elementAt(Vector.java:427) at javax.swing.table.DefaultTableModel.getValueAt(DefaultTableModel.java:632) at javax.swing.JComponent.paint(JComponent.java:1017) at javax.swing.RepaintManager.paint(RepaintManager.java:1220) at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:803) I am assuming that the problem lies in the fact that the second table needs some more time to be populated before I try to get any data from it. That's why I see RepaintManager and paintDirtyRegions in my exceptions. Another thing I did is that I ran my program in debug mode and I put a breakpoint after each population of the 2nd table. Then I pressed F5 to continue for each population of 2nd table and no exception appeared. The program came to it's end without any exceptions. This is another important fact that tells me that maybe in this case I gave the table enough time to be populated. Of course you will ask me: If your program works fine, why do you care about the exceptions? I care for avoiding any future problems and I care to have a better understanding of Java and Java GUI and threads. Why do you depend on a GUI component (and it's model) to get your information and why don't you recreate the resultset that populates your tables using an SQL Query and get your info from the resultset? That would be the best and the right way. The fact is that I have the tables code ready and it was easier for me to just get the info from them. But the right way would be to get everything direct from database. Anyway what I did brought out my question, and answering it would help me understand more things about java. So I posted it.

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• Reliable session faulting for unknown reason

  - by Scarfman007

  I am trying to achieve the following - one client-side proxy instance (kept open) accessed by multiple threads using a reliable session. What I have managed so far is to have either A) a reliable session with a client-side proxy which is created and disposed per call or B) what I aim for, but without a reliable session. When I enable reliable sessions on my binding however, the following behaviour is exhibited: Client-side Upon application startup everything appears to work fine until roughly 18 messages in to the WCF session. I firstly get the proxy.InnerChannel.Faulted event raised, then an exception is caught at the point where I am calling the method on the proxy. The exception is a System.TimeoutException, with message: "The request channel timed out while waiting for a reply after 00:00:59.9062512. Increase the timeout value passed to the call to Request or increase the SendTimeout value on the Binding. The time allotted to this operation may have been a portion of a longer timeout." The inner exception has a similar message: "The request operation did not complete within the allotted timeout of 00:01:00. The time allotted to this operation may have been a portion of a longer timeout." With the method at the top of the inner stack trace being: System.ServiceModel.Channels.ReliableRequestSessionChannel.SyncRequest.WaitForReply(TimeSpan timeout) I then call proxy.Close followed by proxy.Abort (catching and ignoring exceptions). If I utilize the default settings (i.e. have simply <reliableSession/>), then calling proxy. Close results in another System.Timeout exception (although this time the allotted timeout is 00:00:00), however if I override the defaults as specified above no exception is thrown. Service-side Utilizing WCF tracing I get a System.ServiceModel.CommunicationException, with message: "The sequence has been terminated by the remote endpoint. The session has stopped waiting for a particular reply. Because of this the reliable session cannot continue. The reliable session was faulted." And a stack trace ending at: System.ServiceModel.AsyncResult.End[TAsyncResult](IAsyncResult result) When remotely attaching to the server I get the same message, which occurs when code execution steps over the return statement of my service in the service call which causes the error. The puzzling thing to me is that the service is stable and runs with options A) or B) as decribed at the beginning of my post, and occurs after a varying number of messages (around 18). The former fact points to there being nothing wrong with the code (indeed I have checked that no exceptions are thrown), and the latter just serves to confuse me and is why I modified the settings on the reliable session binding. I am quite stuck on this. Can anyone suggest why the reliable session would fault in such a way?

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• C++ Virtual Constructor, without clone()

  - by Julien L.

  I want to perform "deep copies" of an STL container of pointers to polymorphic classes. I know about the Prototype design pattern, implemented by means of the Virtual Ctor Idiom, as explained in the C++ FAQ Lite, Item 20.8. It is simple and straightforward: struct ABC // Abstract Base Class { virtual ~ABC() {} virtual ABC * clone() = 0; }; struct D1 : public ABC { virtual D1 * clone() { return new D1( *this ); } // Covariant Return Type }; A deep copy is then: for( i = 0; i < oldVector.size(); ++i ) newVector.push_back( oldVector[i]->clone() ); Drawbacks As Andrei Alexandrescu states it: The clone() implementation must follow the same pattern in all derived classes; in spite of its repetitive structure, there is no reasonable way to automate defining the clone() member function (beyond macros, that is). Moreover, clients of ABC can possibly do something bad. (I mean, nothing prevents clients to do something bad, so, it will happen.) Better design? My question is: is there another way to make an abstract base class clonable without requiring derived classes to write clone-related code? (Helper class? Templates?) Following is my context. Hopefully, it will help understanding my question. I am designing a class hierarchy to perform operations on a class Image: struct ImgOp { virtual ~ImgOp() {} bool run( Image & ) = 0; }; Image operations are user-defined: clients of the class hierarchy will implement their own classes derived from ImgOp: struct CheckImageSize : public ImgOp { std::size_t w, h; bool run( Image &i ) { return w==i.width() && h==i.height(); } }; struct CheckImageResolution; struct RotateImage; ... Multiple operations can be performed sequentially on an image: bool do_operations( std::vector< ImgOp* > v, Image &i ) { std::for_each( v.begin(), v.end(), /* bind2nd(mem_fun(&ImgOp::run), i ...) don't remember syntax */ ); } int main( ... ) { std::vector< ImgOp* > v; v.push_back( new CheckImageSize ); v.push_back( new CheckImageResolution ); v.push_back( new RotateImage ); Image i; do_operations( v, i ); } If there are multiple images, the set can be split and shared over several threads. To ensure "thread-safety", each thread must have its own copy of all operation objects contained in v -- v becomes a prototype to be deep copied in each thread.

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