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• Is there a JSON library that can serialize Proxy objects?

  - by gmoore

  Using ActiveObjects as my ORM and Gson as my JSON processor. Ran into a problem going toJson from persisted objects. The problem is that my persisted class is actually an Interface and AO is proxying that object under the hood. Here's some sample code: Venue venue = manager.get(Venue.class, id); gson.toJson(venue); Comes up with this exception: java.lang.UnsupportedOperationException: Expecting parameterized type, got interface java.lang.reflect.InvocationHandler. Are you missing the use of TypeToken idiom? See http://sites.google.com/site/gson/gson-user-guide#TOC-Serializing-and... Because venue.getClass().getName() gives: $Proxy228 I've tried a few solutions in various combinations: gsonBuilder.registerTypeAdapter(Venue.class, newVenueSerializer()); Type listType = new TypeToken<Venue>() {}.getType(); Nothing has worked so far and I'm using a wonky field-by-field workaround. Any suggestions? I'm not married to Gson, so if there's an alternative library that can do this I'd be happy to use it.

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• ObjC internals. Why my duck typing attempt failed?

  - by Piotr Czapla

  I've tried to use id to create duck typing in objective-c. The concept looks fine in theory but failed in practice. I was unable to use any parameters in my methods. The methods were called but parameters were wrong. I was getting BAD_ACESS for objects and random values for primitives. I've attached a simple example below. The question: Does any one knows why the methods parameters are wrong? What is happening under the hood of the objective-c? Note: I'm interest in the details. I know how to make the example below work. An example: I've created a simple class Test that is passed to an other class using property id test. @implementation Test - (void) aSampleMethodWithFloat:(float) f andInt: (int) i { NSLog(@"Parameters: %f, %i\n", f, i); } @end Then in the class the following loop is executed: for (float f=0.0f; f < 100.0f ; f += 0.3f) { [self.test aSampleMethodWithOneFloatParameter: f]; // warning: no method found. } Here is the output that I'm getting. As you can see the method was called but the parameters were wrong. Parameters: 0.000000, 0 Parameters: -0.000000, 1069128089 Parameters: -0.000000, 1070176665 Parameters: 2.000000, 1070805811 Parameters: -0.000000, 1071225241 Parameters: 0.000000, 1071644672 Parameters: 2.000000, 1071854387 Parameters: 36893488147419103232.000000, 1072064102 Parameters: -0.000000, 1072273817 Parameters: -36893488147419103232.000000, 1072483532

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• Why is BorderLayout calling setSize() and setBounds()?

  - by ags

  I'm trying to get my head around proper use of the different LayoutManagers to make my GUI design skills more efficient and effective. For me, that usually requires a detailed understanding of what is going on under the hood. I've found some good discussion of the interaction and consequences of a Container using BorderLayout containing a Container using FlowLayout. I understand it for the most part, but wanted to confirm my mental model and to do so I am looking at the code for BorderLayout. In the code snippet below taken from BorderLayout.layoutContainer(), note the calls to the child Component's setSize() method followed by setBounds(). Looking at the source for these methods of Component, setSize() actually calls setBounds() with the current values for Component.x and Component.y. Why is this done (and not entirely redudant?) Doesn't the setBounds() call completely overwrite the results of the setSize() call? if ((c=getChild(NORTH,ltr)) != null) { c.setSize(right - left, c.height); Dimension d = c.getPreferredSize(); c.setBounds(left, top, right - left, d.height); top += d.height + vgap; } I'm also tring to understand where/when the child Component's size is initially set (before the LayoutManager.layoutContainer() method is called). Finally, this post itself raises a "meta-question": in a situation like this, where the source is available elsewhere, is the accepteed protocol to include the entire method? Or some other way to make it easier for folks to participate in the thread? Thanks.

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• How to properly load HTML data from third party website using MVC+AJAX?

  - by Dmitry

  I'm building ASP.NET MVC2 website that lets users store and analyze data about goods found on various online trade sites. When user is filling a form to create or edit an item, he should have a button "Import data" that automatically fills some fields based on data from third party website. The question is: what should this button do under the hood? I see at least 2 possible solutions. First. Do the import on client side using AJAX+jQuery load method. I tried it in IE8 and received browser warning popup about insecure script actions. Of course, it is completely unacceptable. Second. Add method ImportData(string URL) to ItemController class. It is called via AJAX, does the import + data processing server-side and returns JSON-d result to client. I tried it and received server exception (503) Server unavailable when loading HTML data into XMLDocument. Also I have a feeling that dealing with not well-formed HTML (missing closing tags, etc.) will be a huge pain. Any ideas how to parse such HTML documents?

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• What happens when we say "listen to a port" ?

  - by smwikipedia

  Hi, When we start a server application, we always need to speicify the port number it listens to. But how is this "listening mechanism" implemented under the hood? My current imagination is like this: The operating system associate the port number with some buffer. The server application's responsibiligy is to monitor this buffer. If there's no data in this buffer, the server application's listen operation will just block the application. When some data arrives from the wire, the operating system will know that check the data and see if it is targed at this port number. And then it will fill the buffer. And then OS will notify the blocked server application and the server application will get the data and continue to run. Question is: If the above scenario is correct, how could the opearting system know there's data arriving from wire? It cannot be a busy pooling. Is it some kind of interrupt-based mechanism? If there's too much data arriving and the buffer is not big enough, will there be data loss? Is the "listen to a port" operation really a blocking operation? Many thanks.

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• How to hold a queue of messages and have a group of working threads without polling?

  - by Mark

  I have a workflow that I want to looks something like this: / Worker 1 \ =Request Channel= - [Holding Queue|||] - Worker 2 - =Response Channel= \ Worker 3 / That is: Requests come in and they enter a FIFO queue Identical workers then pick up tasks from the queue At any given time any worker may work only one task When a worker is free and the holding queue is non-empty the worker should immediately pick up another task When tasks are complete, a worker places the result on the Response Channel I know there are QueueChannels in Spring Integration, but these channels require polling (which seems suboptimal). In particular, if a worker can be busy, I'd like the worker to be busy. Also, I've considered avoiding the queue altogether and simply letting tasks round-robin to all workers, but it's preferable to have a single waiting line as some tasks may be accomplished faster than others. Furthermore, I'd like insight into how many jobs are remaining (which I can get from the queue) and the ability to cancel all or particular jobs. How can I implement this message queuing/work distribution pattern while avoiding a polling? Edit: It appears I'm looking for the Message Dispatcher pattern -- how can I implement this using Spring/Spring Integration?

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• I'm graduating with a Computer Science degree but I don't feel like I know how to program.

  - by Wendy Peters

  I'm graduating with a Computer Science degree but I see websites like Stackoverflow and search engines like Google and don't know where I'd even begin to write something like that. During one summer I worked as a iPhone developer, but I felt like I was mostly gluing together libraries that other people had written with little understanding of what's happening underneath the hood. I'm trying to improve my knowledge by studying algorithms, but it is a long and painful process. I find algorithms difficult and at the rate I am working through my book it will a decade will have passed before I will finish. Given my current situation, I've spent a month looking for work but my skills (C, Python, Objective-C) are not so desirable in the local market, where C#, Java, and web development are much higher in demand. My GPA is ok (3.0) but it's not high enough to apply to the large companies or return for graduate studies and I don't have a good network of friends. Basically I'm graduating with a Computer Science degree but I don't feel like I know how to program. I thought that joining a company and programming full-time would give me a chance to develop my skills and learn from those more experienced than myself, but I'm struggling to find work and am starting to get really frustrated. I am going to cast my net wider and look beyond the city I've grown up in, but what have other people in similar situation tried to do?

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• Importing external .jar file to Android project

  - by robintw

  I've read various answers to similar questions on StackOverflow, so I apologise if I'm repeating another question, but I can't seem to get this to work. I have a standard java project in which I've written code to parse some BBC Radio XML data from the internet. The project is called BBCSchedules and the class I'm interested in is called BBCChannel. I'm now trying to use the BBCChannel class in an android application. How should I go about doing this? I've tried various things, following various bits of advice on the internet, and the place I've got to at the moment is compiling my BBCSchedules project to a .jar file, and importing that to the Android project using the Build Path/Library/Add External Jar option. However, Eclispe still doesn't recognise the BBCChannel class, and won't let me run the application because of this. I guess I've done something silly wrong, but what is it? Cheers, Robin UPDATE: I've tried the steps listed in http://stackoverflow.com/questions/1334802/how-can-i-use-external-jars-in-an-android-project and various other StackOverflow questions I can find that seem to be related to this, but absolutely nothing seems to work. Any other ideas? UPDATE: The discussions I've had with the author of the first answer below suggest that it is something to do with how I am using Eclipse to attach the .jar file. The project he sent me with the .jar file already attached didn't work. Any other ideas anyone?

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• Javascript XMLHttpRequest Post method

  - by user535617

  Hey So I have a question about posting using an XMLHttpRequest. In theory, if I am to post a username and password to an https domain (which I have yet to get working, unfortunately) would the responseText then change to the next website, or should the text fields become filled in? What normally happens is you navigate to this page via browser, enter a username and password, and it uses a POST method when the submit button is clicked, doing some authentication under the hood and returning a different page. I feel like maybe the responseText should even stay exactly the same (which is what happens now), but I don't know as I have no experience with this kind of thing. this.requests[1].open("POST", "https://" + this.address, true); var query = "target=%2Fcgi-bin%2FStatusConfig.cgi%3FPage%3Dindex&userfile=&username=user&password=pass&log+in=Log+in"; this.requests[1].setRequestHeader("Content-Type", "application/x-www-form-urlencoded"); this.requests[1].setRequestHeader("Content-length", query.length); this.requests[1].setRequestHeader("Keep-Alive", 115); this.requests[1].setRequestHeader("Connection", "keep-alive"); this.requests[1].setRequestHeader("Host", this.address); this.requests[1].send(query); this.requests[1].onreadystatechange = onReadyStateChange1; Then basically onReadyStateChange1 displays the responseText when ready. Any light that could be shed on what SHOULD be happening with the post and responseText would be very appreciated. As would any advice in getting the new, logged into page. For further clarification, what I'm trying to do is log in and then return the new page, because the login page displays only log in information/functionality and the page after logging in has a lot of relevant information. I'm not trying to check the credentials as much as I'm trying to get it (the script) to log in so it can access the next page. Granted, the credentials will have to be valid for that. Thanks all.

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• Best (Java) book for understanding 'under the bonnet' for programming?

  - by Ben

  What would you say is the best book to buy to understand exactly how programming works under the hood in order to increase performance? I've coded in assembly at university, I studied computer architecture and I obviously did high level programming, but what I really dont understand is things like: -what is happening when I perform a cast -whats the difference in performance if I declare something global as opposed to local? -How does the memory layout for an ArrayList compare with a Vector or LinkedList? -Whats the overhead with pointers? -Are locks more efficient than using synchronized? -Would creating my own array using int[] be faster than using ArrayList -Advantages/disadvantages of declaring a variable volatile I have got a copy of Java Performance Tuning but it doesnt go down very low and it contains rather obvious things like suggesting a hashmap instead of using an ArrayList as you can map the keys to memory addresses etc. I want something a bit more Computer Sciencey, linking the programming language to what happens with the assembler/hardware. The reason im asking is that I have an interview coming up for a job in High Frequency Trading and everything has to be as efficient as possible, yet I cant remember every single possible efficiency saving so i'd just like to learn the fundamentals. Thanks in advance

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• JPA - Can an @JoinColumn be an @Id as well? SerializationException occurs.

  - by Shivago

  Hi everyone, I am trying to use an @JoinColumn as an @Id using JPA and I am getting SerializationExceptions, "Could not serialize." UserRole.java: @Entity @Table(name = "authorities") public class UserRole implements Serializable { @Column(name = "authority") private String role; @Id @ManyToOne @JoinColumn(name = "username") private User owner; ... } User.java: @Entity @Table(name = "users") public class User implements Serializable { @Id @GeneratedValue protected Long id; @Column(name = "username") protected String email; @OneToMany(mappedBy = "owner", fetch = FetchType.LAZY, cascade = CascadeType.ALL) protected Set<UserRole> roles = new HashSet<UserRole>(); .... } "username" is set up as a unique index in my Users table but not as the primary key. Is there any way to make "username" act as the ID for UserRole? I don't want to introduce a numeric key in UserRole. Have I totally lost the plot here? I am using MySQL and Hibernate under the hood.

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• How do software events work internally?

  - by Duddle

  Hello! I am a student of Computer Science and have learned many of the basic concepts of what is going on "under the hood" while a computer program is running. But recently I realized that I do not understand how software events work efficiently. In hardware, this is easy: instead of the processor "busy waiting" to see if something happened, the component sends an interrupt request. But how does this work in, for example, a mouse-over event? My guess is as follows: if the mouse sends a signal ("moved"), the operating system calculates its new position p, then checks what program is being drawn on the screen, tells that program position p, then the program itself checks what object is at p, checks if any event handlers are associated with said object and finally fires them. That sounds terribly inefficient to me, since a tiny mouse movement equates to a lot of cpu context switches (which I learned are relatively expensive). And then there are dozens of background applications that may want to do stuff of their own as well. Where is my intuition failing me? I realize that even "slow" 500MHz processors do 500 million operations per second, but still it seems too much work for such a simple event. Thanks in advance!

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• XSL(like) declarative language as MVC view over strongtyped model?

  - by Martin Kool

  As a huge XSL fan, I am very happy to use xsl as the view in our proprietary MVC framework on ASP.NET. Objects in the model are serialized under the hood using .NET's xml serializer, and we use quite atomic xsl templates to declare how each object or property should transform. For example: <xsl:template match="/Article"> <html> <body> <div class="article"> <xsl:apply-templates /> </div> </body> </html> </xsl:template> <xsl:template match="Article/Title"> <h1> <xsl:apply-templates /> </h1> </xsl:template> <xsl:template match="@*|text()"> <xsl:copy /> </xsl:template> This mechanism allows us to quickly override default matching templates, like having a template matching on the last item in a list, or the selected one, etc. Also, xsl extension objects in .NET allow us just the bit of extra grip that we need. Common shared templates can be split up and included. However Even though I can ignore the verbosity downside of xsl (because Visual Studio schema intellisense + snippets really is slick, praise to the VS-team), the downside of not having intellisense over strongtyped objects in the model is really something that's bugging me. I've seen ASP.NET MVC + user controls in action and really starting to love it, but I wonder; Is there a way of getting some sort of intellisense over XML that we're iterating over, or do you know of a language that offers the freedom and declarativeness of XSL but has the strongtype/intellisense benefits of say webforms/usercontrols/asp.net.mvc-view? (I probably know the answer: "no", and I'll find myself using Phil Haack's utterly cool mvc shizzle soon...)

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• How do I call C++/CLI (.NET) DLLs from standard, unmanaged non-.NET applications?

  - by tronjohnson

  In the unmanaged world, I was able to write a __declspec(dllexport) or, alternatively, use a .DEF file to expose a function to be able to call a DLL. (Because of name mangling in C++ for the __stdcall, I put aliases into the .DEF file so certain applications could re-use certain exported DLL functions.) Now, I am interested in being able to expose a single entry-point function from a .NET assembly, in unmanaged-fashion, but have it enter into .NET-style functions within the DLL. Is this possible, in a simple and straight-forward fashion? What I have is a third-party program that I have extended through DLLs (plugins) that implement some complex mathematics. However, the third-party program has no means for me to visualize the calculations. I want to somehow take these pre-written math functions, compile them into a separate DLL (but using C++/CLI in .NET), but then add hooks to the functions so I can render what's going on under the hood in a .NET user control. I'm not sure how to blend the .NET stuff with the unmanaged stuff, or what to Google to accomplish this task. Specific suggestions with regard to the managed/unmanaged bridge, or alternative methods to accomplish the rendering in the manner I have described would be helpful. Thank you.

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• In C# should I reuse a function / property parameter to compute cleaner temporary value or create a

  - by Hamish Grubijan

  The example below may not be problematic as is, but it should be enough to illustrate a point. Imagine that there is a lot more work than trimming going on. public string Thingy { set { // I guess we can throw a null reference exception here on null. value = value.Trim(); // Well, imagine that there is so much processing to do this.thingy = value; // That this.thingy = value.Trim() would not fit on one line ... So, if the assignment has to take two lines, then I either have to abusereuse the parameter, or create a temporary variable. I am not a big fan of temporary variables. On the other hand, I am not a fan of convoluted code. I did not include an example where a function is involved, but I am sure you can imagine it. One concern I have is if a function accepted a string and the parameter was "abused", and then someone changed the signature to ref in both places - this ought to mess things up, but ... who would knowingly make such a change if it already worked without a ref? Seems like it is their responsibility in this case. If I mess with the value of value, am I doing something non-trivial under the hood? If you think that both approaches are acceptable, then which do you prefer and why? Thanks.

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• Correct way to initialize dynamic Array in C++

  - by mef

  Hey guys, I'm currently working on a C++ project, where dynamic arrays often appear. I was wondering, what could be the correct way to initialize a dynamic array using the new-operator? A colleague of mine told me that it's a no-no to use new within the constructor, since a constructor is a construct that shouldn't be prone to errors or shouldn't fail at all, respectively. Now let's consider the following example: We have two classes, a more or less complex class State and a class StateContainer, which should be self-explained. class State { private: unsigned smth; public: State(); State( unsigned s ); }; class StateContainer { private: unsigned long nStates; State *states; public: StateContainer(); StateContainer( unsigned long n ); virtual ~StateContainer(); }; StateContainer::StateContainer() { nStates = SOME_DEFINE_N_STATES; states = new State[nStates]; if ( !states ) { // Error handling } } StateContainer::StateContainer( unsigned long n ) { nStates = n; try { states = new State[nStates] } catch ( std::bad_alloc &e ) { // Error handling } } StateContainer::~StateContainer() { if ( states ) { delete[] states; states = 0; } } Now actually, I have two questions: 1.) Is it ok, to call new within a constructor, or is it better to create an extra init()-Method for the State-Array and why? 2.) Whats the best way to check if new succeeded: if (!ptr) std::cerr << "new failed." or try { /*new*/ } catch (std::bad_alloc) { /*handling*/ } 3.) Ok its three questions ;o) Under the hood, new does some sort of ptr = (Struct *)malloc(N*sizeof(Struct)); And then call the constructor, right?

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• Varnish configuration to only cache for non-logged in users

  - by davidsmalley

  I have a Ruby on Rails application fronted by varnish+nginx. As most of the sites content is static unless you are a logged in user, I want to cache the site heavily with varnish when a user is logged out but only to cache static assets when they are logged in. When a user is logged in they will have the cookie 'user_credentials' present in their Cookie: header, in addition I need to skip caching on /login and /sessions in order that a user can get their 'user_credentials' cookie in the first place. Rails by default does not set a cache friendly Cache-control header, but my application sets a "public,s-max-age=60" header when a user is not logged in. Nginx is set to return 'far future' expires headers for all static assets. The configuration I have at the moment is totally bypassing the cache for everything when logged in, including static assets — and is returning cache MISS for everything when logged out. I've spent hours going around in circles and here is my current default.vcl director rails_director round-robin { { .backend = { .host = "xxx.xxx.xxx.xxx"; .port = "http"; .probe = { .url = "/lbcheck/lbuptest"; .timeout = 0.3 s; .window = 8; .threshold = 3; } } } } sub vcl_recv { if (req.url ~ "^/login") { pipe; } if (req.url ~ "^/sessions") { pipe; } # The regex used here matches the standard rails cache buster urls # e.g. /images/an-image.png?1234567 if (req.url ~ "\.(css|js|jpg|jpeg|gif|ico|png)\??\d*$") { unset req.http.cookie; lookup; } else { if (req.http.cookie ~ "user_credentials") { pipe; } } # Only cache GET and HEAD requests if (req.request != "GET" && req.request != "HEAD") { pipe; } } sub vcl_fetch { if (req.url ~ "^/login") { pass; } if (req.url ~ "^/sessions") { pass; } if (req.http.cookie ~ "user_credentials") { pass; } else { unset req.http.Set-Cookie; } # cache CSS and JS files if (req.url ~ "\.(css|js|jpg|jpeg|gif|ico|png)\??\d*$") { unset req.http.Set-Cookie; } if (obj.status >=400 && obj.status <500) { error 404 "File not found"; } if (obj.status >=500 && obj.status <600) { error 503 "File is Temporarily Unavailable"; } } sub vcl_deliver { if (obj.hits > 0) { set resp.http.X-Cache = "HIT"; } else { set resp.http.X-Cache = "MISS"; } }

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• Benchmark MySQL Cluster using flexAsynch: No free node id found for mysqld(API)?

  - by quanta

  I am going to benchmark MySQL Cluster using flexAsynch follow this guide, details as below: mkdir /usr/local/mysqlc732/ cd /usr/local/src/mysql-cluster-gpl-7.3.2 cmake . -DCMAKE_INSTALL_PREFIX=/usr/local/mysqlc732/ -DWITH_NDB_TEST=ON make make install Everything works fine until this step: # /usr/local/mysqlc732/bin/flexAsynch -t 1 -p 80 -l 2 -o 100 -c 100 -n FLEXASYNCH - Starting normal mode Perform benchmark of insert, update and delete transactions 1 number of concurrent threads 80 number of parallel operation per thread 100 transaction(s) per round 2 iterations Load Factor is 80% 25 attributes per table 1 is the number of 32 bit words per attribute Tables are with logging Transactions are executed with hint provided No force send is used, adaptive algorithm used Key Errors are disallowed Temporary Resource Errors are allowed Insufficient Space Errors are disallowed Node Recovery Errors are allowed Overload Errors are allowed Timeout Errors are allowed Internal NDB Errors are allowed User logic reported Errors are allowed Application Errors are disallowed Using table name TAB0 NDBT_ProgramExit: 1 - Failed ndb_cluster.log: WARNING -- Failed to allocate nodeid for API at 127.0.0.1. Returned eror: 'No free node id found for mysqld(API).' I also have recompiled with -DWITH_DEBUG=1 -DWITH_NDB_DEBUG=1. How can I run flexAsynch in the debug mode? # /usr/local/mysqlc732/bin/flexAsynch -h FLEXASYNCH Perform benchmark of insert, update and delete transactions Arguments: -t Number of threads to start, default 1 -p Number of parallel transactions per thread, default 32 -o Number of transactions per loop, default 500 -l Number of loops to run, default 1, 0=infinite -load_factor Number Load factor in index in percent (40 -> 99) -a Number of attributes, default 25 -c Number of operations per transaction -s Size of each attribute, default 1 (PK is always of size 1, independent of this value) -simple Use simple read to read from database -dirty Use dirty read to read from database -write Use writeTuple in insert and update -n Use standard table names -no_table_create Don't create tables in db -temp Create table(s) without logging -no_hint Don't give hint on where to execute transaction coordinator -adaptive Use adaptive send algorithm (default) -force Force send when communicating -non_adaptive Send at a 10 millisecond interval -local 1 = each thread its own node, 2 = round robin on node per parallel trans 3 = random node per parallel trans -ndbrecord Use NDB Record -r Number of extra loops -insert Only run inserts on standard table -read Only run reads on standard table -update Only run updates on standard table -delete Only run deletes on standard table -create_table Only run Create Table of standard table -drop_table Only run Drop Table on standard table -warmup_time Warmup Time before measurement starts -execution_time Execution Time where measurement is done -cooldown_time Cooldown time after measurement completed -table Number of standard table, default 0

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• $PATH is driving me nuts

  - by Chris4d

  OK, apologies if this is something dumb, but I'm running out of ideas. Goal: prepend /usr/local/bin to $PATH Problem: $PATH won't do what I want or expect How I got here: I want to start learning to program, so I'm getting comfortable messing around under the hood, but don't have a lot of experience. I installed the fish shell (because it's friendly!) using homebrew and set it as my default shell (under system prefs>users & groups>advanced). At some point, I ran brew doctor to see if my installs were all kosher, and it suggested I move /usr/local/bin to the front of $PATH so that I could use my installation of git rather than the system copy. Fine - but between path_helper and fish, something was happening to $PATH that was out of my control, and I could never get the paths arranged in the right way. Environment: OSX 10.8.2, upgraded from 10.7ish, with xcode and devtools installed, plus x11, homebrew, and fish More info: I've set my user's default shell back to bash, and tried a variety of shells thru terminal.app - bash, fish, sh. I moved /usr/local/bin to the top of /etc/paths but it didn't change anything. I looked thru the various config.fish files and commented out stuff that might mess with $PATH, didn't help. I have the following files in /etc/paths.d/: ./10-homebrew containing /usr/local/bin ./20-fish containing /usr/local/Cellar/fish/1.23.1/bin ./40-XQuartz containing /opt/X11/bin I added set +x to my profile and when I start terminal.app I get: Last login: Mon Oct 1 13:31:06 on ttys000 + '[' -x /usr/libexec/path_helper ']' + eval '/usr/libexec/path_helper -s' ++ /usr/libexec/path_helper -s PATH="/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/Cellar/fish/1.23.1/bin:/opt/X11/bin"; export PATH; + '[' /bin/bash '!=' no ']' + '[' -r /etc/bashrc ']' + . /etc/bashrc ++ '[' -z '\s-\v\$ ' ']' ++ PS1='\h:\W \u\$ ' ++ shopt -s checkwinsize ++ '[' Apple_Terminal == Apple_Terminal ']' ++ '[' -z '' ']' ++ PROMPT_COMMAND='update_terminal_cwd; ' ++ update_terminal_cwd ++ local 'SEARCH= ' ++ local REPLACE=%20 ++ local PWD_URL=file://Chriss-iMac.local/Users/c4 ++ printf '\e]7;%s\a' file://Chriss-iMac.local/Users/c4 Chriss-iMac:~ c4$ So it looks like path_helper runs, but then running echo $PATH nets me /usr/bin:/bin:/usr/sbin:/sbin. So, it looks like path_helper isn't even doing what it's supposed to anymore? I'm sure there is some well-defined behavior here that I don't understand, or I borked something while trying to fix it. Please help!

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• High CPU usage - symptoms moving from server to server after bouncing

  - by grt3kl

  First off, I apologize if I didn't include enough information to properly troubleshoot this issue. This sort of thing isn't my specialty, so it is a learning process. If there's something I need to provide, please let me know and I'll be happy to do what I can. The images associated with my question are at the bottom of this post. We are dealing with a clustered environment of four WebLogic 9.2 Java application servers. The cluster utilizes a round-robin load algorithm. Other details include: Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_12-b04) BEA JRockit(R) (build R27.4.0-90_CR352234-91983-1.5.0_12-20071115-1605-linux-x86_64, compiled mode) Basically, I started looking at the servers' performance because our customers are seeing lots of lag at various times of the day. Our servers should easily handle the loads they are given, so it's not clear what's going on. Using HP Performance Manager, I generated some graphs that indicate that the CPU usage is completely out of whack. It seems that, at any given point, one or more of the servers has a CPU utilization of over 50%. I know this isn't particularly high, but I would say it is a red flag based on the CPU utilization of the other servers in the WebLogic cluster. Interesting things to note: The high CPU utilization was occurring only on server02 for several weeks. The server crashed (extremely rare; we are not sure if it's related to this) and upon starting it back up, the CPU utilization was normal on all 4 servers. We restarted all 4 managed servers and the application server (on server01) yesterday, on 2/28. As you can see, server03 and server04 picked up the behavior that was seen on server02 before. The CPU utilization is a Java process owned by the application user (appown). The number of transactions is consistent across all servers. It doesn't seem like any one server is actually handling more than another. If anyone has any ideas or can at least point me in the right direction, that would be great. Again, please let me know if there is any additional information I should post. Thanks!

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• How to tune system settings for mongoDB on Linux?

  - by jsh

  Trying to squeeze a lot out of one question here -- please bear with me. Although the MongoDB man pages make several useful recommendations about system settings like ulimit (http://docs.mongodb.org/manual/reference/ulimit/), and other production factors (http://docs.mongodb.org/manual/administration/production-notes/) they seem mysteriously silent on things like virtual memory and swap settings. The closest we get to a hint is that "...the operating system’s virtual memory subsystem manages MongoDB’s memory..." (http://docs.mongodb.org/manual/faq/fundamentals/#does-mongodb-require-a-lot-of-ram). Running the same job - high writes and high reads on about 10,000,000 records in a single collection -- on my 4-processor, 4GB RAM macbook and an 8-core ubuntu box with 64GB RAM I saw dramatically WORSE read performance on the linux box with factory settings, and could hear the disk constantly spinning, indicating high I/O and presumably swapping. Yes, other things were happening on the box, but there was plenty of free RAM, disk space, etc.; furthermore, I did not see evidence that Mongo was expanding to take advantage of all that free RAM as it is touted to do. Linux box default settings were as follows: vm.swappiness =60 vm.dirty_background_ratio = 10 vm.dirty_ratio = 20 vm.dirty_expire_centisecs =3000 vm.dirty_writeback_centisecs=500 I hazarded some guesses looking at docs and blogs for other types of databases (Oracle, MYSQL, etc.), experimented, and adjusted as below. vm.swappiness=10 vm.dirty_background_ratio=5 vm.dirty_ratio=5 vm.dirty_writeback_centisecs=250 vm.dirty_expire_centisecs=500 I saw some immediate apparent improvements in read time. However, when I ran my test jobs again, read performance continued to be painfully sluggish during heavy writes. Then, I REBUILT the collection from an available data source - and suddenly I can read at 1ms or less per record WHILE doing the write job! So the question is really two-fold: 1) What are appropriate VM settings for MongoDB on Linux? 2) (bonus) Does Mongo do some checking or optimization with the OS while data is being built? In other words, if I have built a large data set with suboptimal VM or I/O settings, does Mongo make assumptions during the memory-mapping process that will fail to take advantage of optimizations down the road? Obviously I don't fully grok memory mapping under the hood (I was hoping I wouldn't have to). Any help appreciated...thanks! -j

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• Migrating Split Access Database from one domain to another (not working, details in Q)

  - by Expo_Rob

  Some background: I'm a programmer, not a network administrator, who has been asked to migrate some accounting software (Integrated Office Accounting version 3.2) from an existing domain (OLD_NETWORK) to a new domain (NEW_NETWORK). No-body at the office knows how it works under the hood. It is a split Access 2000 database with the back-end shared and on a file server (which is also the DC) using mapped drives. The DC is NT Server 4 SP 6. The new server is server 2003. The two networks are running independently (ie: two computers on each desk). I have been able to get new computers set up on NEW_NETWORK and working with the IOA software just perfectly but for one problem: The company here uses other entirely separate databases which access the tables IOA maintains (specifically the 'customers' table) via links. To switch between these systems, you press F11 then File-Open the appropriate database and away you go (this is necessary to maintain the permissions that the IOA system uses to protect the customers table). The entire database is Access 2000, the links go to other Access databases, SQL-Server is not involved in any way, nor is a migration to SQL server likely. If I can't migrate anything over, everything will stay as it is, and the NEW_NETWORK computers will not be used. The problem: When I try and update these seperate databases (I shall call one "BANK_ACCOUNT", but the name does not matter), it says "this recordset cannot be updated". It also will sometimes not pull information out of the 'customers' table (ie: date_entered) when looking at a report of everyone who opened a bank account on a certain day (ie: today). I have tried: Giving 'everyone' full control via. shared directory permissions Giving 'everyone' full control on a file system level Checking the permissions within Access (everyone has full read/write on all tables) Copying the entire server contents from one file server to another (ie: xcopy everything) Copying the entire local client files from one computer to another, putting them in the exact same position in the file system, with the same permissons (or full control to 'everyone'). Running as an Administrator Taking one of the NEW_NETWORK computers, having it join OLD_NETWORK and run the software (direct copy from a working system with identical drive mappings), this did not work Weeping openly My Question: Is there anything else I can try? (sorry for this being so long)

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• MySQL 5.5 brings in new ways to authenticate users

  - by Georgi Kodinov

  Ever wanted to use your server's OS for authenticating MySQL users ? Or the corporate LDAP repository ? Unfortunately options like the above are plentiful nowadays. And providing hard-coded support for protocol X or service Y is not the best possible idea. MySQL 5.5 has taken the step into the right direction by providing an infrastructure allowing one to make the server understand different authentication protocols by creating a set of simple plugins (one for the client and one for the server). So now you can easily extend MySQL to search for and authenticate users in your favorite user directory. In fact the API supplied is so versatile that we took the possibility to re-design the current "native" authentication mechanism into a built-in always-on plugin ! OK, let me give you an example: Imagine we have a bunch of users defined in your OS, e.g. we have a user joro with his respective password. And we have a MySQL instance running on the same computer. It would not be unexpected to need to let joro access and/or modify MySQL data. The first step is to define him as a MySQL user. And there's a problem right there : MySQL's CREATE USER joro@localhost IDENTIFIED BY 'joros_password' statement needs a password. And this is a password in no way related to the password that joro have set up in the OS. What's worse : if joro changes his OS password this will in no way be reflected in MySQL. So he'll need to change his MySQL password in a separate step. Not very convenient, specially when you have a lot of users. This is a laborious setup for joro's DBA as well : he'll have to disable his access in both MySQL and the OS should he decides that joro's out of the "nice" list. Now mysql 5.5 to the rescue: Imagine that the smart DBA has created a MySQL server plugin that will check if the name of the user logging in is a valid and enabled OS name and if the password supplied to the mysql client matches the OS and has called this plugin 'auth_os'. Now all that's left to do is to define joro as a MySQL user that will be authenticated externally. This is done by the following command : CREATE USER 'joro'@'localhost' IDENTIFIED WITH 'auth_os'; Now joro can login to MySQL using his current OS password. Note : joro is still a valid MySQL user, so you can grant privileges to him just like you would for all other users. What's better: you can have users that authenticate using different mechanisms in the same server. So you can e.g. safely experiment with external authentication for selected users while keeping your current user base operational. What happens under the hood when joro logs in ? The server will find out by the user definition that it needs to use a non-default authentication and will ask the client to "switch" to using the appropriate client-side plugin (if of course the client is not already using it). If the client can't do this (e.g. because it's an old client or doesn't have the necessary plugin available) the server will reject the login. Otherwise the server will let the server-side plugin decide (while possibly talking to the client side plugin and the OS user directory) if this is a valid login or not. If it is the login process will continue as usual, while if it's not the login will get rejected. There's a lot more that MySQL 5.5 can do for you than just the simple case above. Stay tuned for more advanced use cases like mapping groups of external users to a single MySQL user (so you won't have to have 1-to-1 mapping between your external user directory and your mysql user repository) or ways to control the process as a DBA. Or you can simply skip ahead and read the relevant topics from MySQL's excellent online documentation. Or take a look at the example plugins in plugin/auth. Or take a look at the test suite in mysql-test/t/plugin_auth.test. Changelog entry: http://dev.mysql.com/doc/refman/5.5/en/news-5-5-7.html Primary new sections: Pluggable authentication Proxy users Client plugin C API functions Revised sections: New PROXY privilege New proxies_priv grant table Passwords might be external New external_user and proxy_user system variables New --default-auth and --plugin-dir mysql options New MYSQL_DEFAULT_AUTH and MYSQL_PLUGIN_DIR options for mysql_options() CREATE USER has IDENTIFIED WITH clause to specify auth plugin GRANT has PROXY privilege, IDENTIFIED WITH clause to specify auth plugin The data structure for writing client plugins

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• What’s New for Oracle Commerce? Executive QA with John Andrews, VP Product Management, Oracle Commerce

  - by Katrina Gosek

  Oracle Commerce was for the fifth time positioned as a leader by Gartner in the Magic Quadrant for E-Commerce. This inspired me to sit down with Oracle Commerce VP of Product Management, John Andrews to get his perspective on what continues to make Oracle a leader in the industry and what’s new for Oracle Commerce in 2013. Q: Why do you believe Oracle Commerce continues to be a leader in the industry? John: Oracle has a great acquisition strategy – it brings best-of-breed technologies into the product fold and then continues to grow and innovate them. This is particularly true with products unified into the Oracle Commerce brand. Oracle acquired ATG in late 2010 – and then Endeca in late 2011. This means that under the hood of Oracle Commerce you have market-leading technologies for cross-channel commerce and customer experience, both designed and developed in direct response to the unique challenges online businesses face. And we continue to innovate on capabilities core to what our customers need to be successful – contextual and personalized experience delivery, merchant-inspired tools, and architecture for performance and scalability. Q: It’s not a slow moving industry. What are you doing to keep the pace of innovation at Oracle Commerce? John: Oracle owes our customers the most innovative commerce capabilities. By unifying the core components of ATG and Endeca we are delivering on this promise. Oracle Commerce is continuing to innovate and redefine how commerce is done and in a way that drive business results and keeps customers coming back for experiences tailored just for them. Our January and May 2013 releases not only marked the seventh significant releases for the solution since the acquisitions of ATG and Endeca, we also continue to demonstrate rapid and significant progress on the unification of commerce and customer experience capabilities of the two commerce technologies. Q: Can you tell us what was notable about these latest releases under the Oracle Commerce umbrella? John: Specifically, our latest product innovations give businesses selling online the ability to get to market faster with more personalized commerce experiences in the following ways: Mobile: the latest Commerce Reference Application in this release offers a wider range of examples for online businesses to leverage for iOS development and specifically new iPad reference capabilities. This release marks the first release of the iOS Universal application that serves both the iPhone and iPad devices from a single download or binary. Business users can now drive page content management and layout of search results and category pages, as well as create additional storefront elements such as categories, facets / dimensions, and breadcrumbs through Experience Manager tools. Cross-Channel Commerce: key commerce platform capabilities have been added to support cross-channel commerce, including an expanded inventory model to maintain inventory for stores, pickup in stores and Web-based returns. Online businesses with in-store operations can now offer advanced shipping options on the web and make returns and exchange logic easily available on the web. Multi-Site Capabilities: significant enhancements to the Commerce Platform multi-site architecture that allows business users to quickly launch and manage multiple sites on the same cluster and share data, carts, and other components. First introduced in 2010, with this latest release business users can now partition or share customer profiles, control users’ site-based access, and manage personalization assets using site groups. Internationalization: continued language support and enhancements for business user tools as well and search and navigation. Guided Search now supports 35 total languages with 11 new languages (including Danish, Arabic, Norwegian, Serbian Cyrillic) added in this release. Commerce Platform tools now include localized support for 17 locales with 4 new languages (Danish, Portuguese (European), Finnish, and Thai). No development or customization is required in order for business users to use the applications in any of these supported languages. Business Tool Experience: valuable new Commerce Merchandising features include a new workflow for making emergency changes quickly and increased visibility into promotions rules and qualifications in preview mode. Oracle Commerce business tools continue to become more and more feature rich to provide intuitive, easy- to-use (yet powerful) capabilities to allow business users to manage content and the shopping experience. Commerce & Experience Unification: demonstrable unification of commerce and customer experience capabilities include – productized cartridges that provide supported integration between the Commerce Platform and Experience Management tools, cross-channel returns, Oracle Service Cloud integration, and integrated iPad application. The mission guiding our product development is to deliver differentiated, personalized user experiences across any device in a contextual manner – and to give the business the best tools to tune and optimize those user experiences to meet their business objectives. We also need to do this in a way that makes it operationally efficient for the business, keeping the overall total cost of ownership low – yet also allows the business to expand, whether it be to new business models, geographies or brands. To learn more about the latest Oracle Commerce releases and mission, visit the links below: • Hear more from John about the Oracle Commerce mission • Hear from Oracle Commerce customers • Documentation on the new releases • Listen to the Oracle ATG Commerce 10.2 Webcast • Listen to the Oracle Endeca Commerce 3.1.2 Webcast

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• BizTalk host throttling &ndash; Singleton pattern and High database size

  - by S.E.R.

  Originally posted on: http://geekswithblogs.net/SERivas/archive/2013/06/30/biztalk-host-throttling-ndash-singleton-pattern-and-high-database-size.aspxI have worked for some days around the singleton pattern (for those unfamiliar with it, read this post by Victor Fehlberg) and have come across a few very interesting posts, among which one dealt with performance issues (here, also by Victor Fehlberg). Simply put: if you have an orchestration which implements the singleton pattern, then performances will continuously decrease as the orchestration receives and consumes messages, and that behavior is more obvious when the orchestration never ends (ie : it keeps looping and never terminates or completes). As I experienced the same kind of problem (actually I was alerted by SCOM, which told me that the host was being throttled because of High database size), I thought it would be a good idea to dig a little bit a see what happens deep inside BizTalk and thus understand the reasons for this behavior. NOTE: in this article, I will focus on this High database size throttling condition. I will try and work on the other conditions in some not too distant future… Test conditions The singleton orchestration For the purpose of this study, I have created the following orchestration, which is a very basic implementation of a singleton that piles up incoming messages, then does something else when a certain timeout has been reached without receiving another message: Throttling settings I have two distinct hosts : one that hosts the receive port (basic FILE port) : Ports_ReceiveHostone that hosts the orchestration : ProcessingHost In order to emphasize the throttling mechanism, I have modified the throttling settings for each of these hosts are as follows (all other parameters are set to the default value): [Throttling thresholds] Message count in database: 500 (default value : 50000) Evolution of performance counters when submitting messages Since we are investigating the High database size throttling condition, here are the performance counter that we should take a look at (all of them are in the BizTalk:Message Agent performance object): Database sizeHigh database sizeMessage delivery throttling stateMessage publishing throttling stateMessage delivery delay (ms)Message publishing delay (ms)Message delivery throttling state durationMessage publishing throttling state duration (If you are not used to Perfmon, I strongly recommend that you start using it right now: it is a wonderful tool that allows you to open the hood and see what is going on inside BizTalk – and other systems) Database size It is quite obvious that we will start by watching the database size and high database size counters, just to see when the first reaches the configured threshold (500) and when the second rings the alarm. NOTE : During this test I submitted 600 messages, one message at a time every 10ms to see the evolution of the counters we have previously selected. It might not show very well on this screenshot, but here is what happened: From 15:46:50 to 15:47:50, the database size for the Ports_ReceiveHost host (blue line) kept growing until it reached a maximum of 504.At 15:47:50, the high database size alert fires At first I was surprised by this result: why is it the database size of the receiving host that keeps growing since it is the processing host that piles up messages? Actually, it makes total sense. This counter measures the size of the database queue that is being filled by the host, not consumed. Therefore, the high database size alert is raised on the host that fills the queue: Ports_ReceiveHost. More information is available on the Public MPWiki page. Now, looking at the Message publishing throttling state for the receiving host (green line), we can see that a throttling condition has been reached at 15:47:50: We can also see that the Message publishing delay(ms) (blue line) has begun growing slowly from this point. All of this explains why performances keep decreasing when a singleton keeps processing new messages: the database size grows and when it has exceeded the Message count in database threshold, the host is throttled and the publishing delay keeps increasing. Digging further So, what happens to the database queue then? Is it flushed some day or does it keep growing and growing indefinitely? The real question being: will the host be throttled forever because of this singleton? To answer this question, I set the Message count in database threshold to 20 (this value is very low in order not to wait for too long, otherwise I certainly would have fallen asleep in front of my screen) and I submitted 30 messages. The test was started at 18:26. At 18:56 (ie : exactly 30min later) the throttling was stopped and the database size was divided by 2. 30 min later again, the database size had dropped to almost zero: I guess I’ll have to find some documentation and do some more testing before I sort this out! My guess is that some maintenance job is at work here, though I cannot tell which one Digging even further If we take a look at the Message delivery throttling state counter for the processing host, we can see that this host was also throttled during the submission of the 600 documents: The value for the counter was 1, meaning that Message delivery incoming rate for the host instance exceeds the Message delivery outgoing rate * the specified Rate overdrive factor (percent) value. We will see this another day… :) A last word Let’s end this article with a warning: DO NOT CHANGE THE THROTTLING SETTINGS LIGHTLY! The temptation can be great to just bypass throttling by setting very high values for each parameter (or zero in some cases, which simply disables throttling). Nevertheless, always keep in mind that this mechanism is here for a very good reason: prevent your BizTalk infrastructure from exploding!! So whatever you do with those settings, do a lot of testing and benchmarking!

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