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• Simple continuously running XMPP client in python

  - by tom

  I'm using python-xmpp to send jabber messages. Everything works fine except that every time I want to send messages (every 15 minutes) I need to reconnect to the jabber server, and in the meantime the sending client is offline and cannot receive messages. So I want to write a really simple, indefinitely running xmpp client, that is online the whole time and can send (and receive) messages when required. My trivial (non-working) approach: import time import xmpp class Jabber(object): def __init__(self): server = 'example.com' username = 'bot' passwd = 'password' self.client = xmpp.Client(server) self.client.connect(server=(server, 5222)) self.client.auth(username, passwd, 'bot') self.client.sendInitPresence() self.sleep() def sleep(self): self.awake = False delay = 1 while not self.awake: time.sleep(delay) def wake(self): self.awake = True def auth(self, jid): self.client.getRoster().Authorize(jid) self.sleep() def send(self, jid, msg): message = xmpp.Message(jid, msg) message.setAttr('type', 'chat') self.client.send(message) self.sleep() if __name__ == '__main__': j = Jabber() time.sleep(3) j.wake() j.send('[email protected]', 'hello world') time.sleep(30) The problem here seems to be that I cannot wake it up. My best guess is that I need some kind of concurrency. Is that true, and if so how would I best go about that? EDIT: After looking into all the options concerning concurrency, I decided to go with twisted and wokkel. If I could, I would delete this post.

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• Unhandled Exception error message

  - by Joshua Green

  Does anyone know why including a term such as: t = PL_new_term_ref(); would cause an Unhandled Exception error message: 0xC0000005: Access violation reading location 0x0000000c. (Visual Studio 2008) I have a header file: class UserTaskProlog : public ArAction { public: UserTaskProlog( const char* name = " sth " ); ~UserTaskProlog( ); AREXPORT virtual ArActionDesired *fire( ArActionDesired currentDesired ); private: term_t t; }; and a cpp file: UserTaskProlog::UserTaskProlog( const char* name ) : ArAction( name, " sth " ) { char** argv; argv[ 0 ] = "libpl.dll"; PL_initialise( 1, argv ); PlCall( "consult( 'myProg.pl' )" ); } UserTaskProlog::~UserTaskProlog( ) { } ArActionDesired *UserTaskProlog::fire( ArActionDesired currentDesired ) { cout << " something " << endl; t = PL_new_term_ref( ); } Without t=PL_new_term_ref() everything works fine, but when I start adding my Prolog code (declarations first, such as t=PL_new_term_ref), I get this Access Violation error message. I'd appreciate any help. Thanks,

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• How to use db4o IObjectContainer in a web application ? (Container lifetime ?)

  - by driis

  I am evaluating db4o for persistence for a ASP .NET MVC project. I am wondering how I should use the IObjectContainer in a web context with regards to object lifetime. As I see it, I can do one of the following: Create the IObjectContainer at application startup and keep the same instance for the entire application lifetime. Create one IObjectContainer per request. Start a server, and get a client IObjectContainer for each database interaction. What are the implications of these options, in terms of performance and concurrency ? Since the database is locked when an IObjectContainer is opened, I am pretty sure that option 2) would get me some problems with concurrency - would this also be the case for option 1 ? As I understand it, if I retrieve an object from an IObjectContainer, it must be saved by the same IObjectContainer instance - in order for db4o to identify it as being the same object. Therefore, If I choose option 3), I would have to retrieve the original object, make the necessary changes (copy data from a modified object), and then store it using the same IObjectContainer. Is this true ?

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• Noise with multi-threaded raytracer

  - by herber88

  This is my first multi-threaded implementation, so it's probably a beginners mistake. The threads handle the rendering of every second row of pixels (so all rendering is handled within each thread). The problem persists if the threads render the upper and lower parts of the screen respectively. Both threads read from the same variables, can this cause any problems? From what I've understood only writing can cause concurrency problems... Can calling the same functions cause any concurrency problems? And again, from what I've understood this shouldn't be a problem... The only time both threads write to the same variable is when saving the calculated pixel color. This is stored in an array, but they never write to the same indices in that array. Can this cause a problem? Multi-threaded rendered image (Spam prevention stops me from posting images directly..) Ps. I use the exactly same implementation in both cases, the ONLY difference is a single vs. two threads created for the rendering.

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• Implicit linking vs. explicit linking of DLL in Delphi

  - by Tom

  I'm having trouble getting my dll to work when using explicit linking. Using implicit linking it works fine. Would someone google me a solution? :) No, just kidding, here's my code: This code works fine: function CountChars(_s: Pchar): integer; StdCall; external 'sample_dll.dll'; procedure TForm1.Button1Click(Sender: TObject); begin ShowMessage(IntToStr(CountChars('Hello world'))); end; This code doesn't work (I get an access violation): procedure TForm1.Button1Click(Sender: TObject); var LibHandle: HMODULE; CountChars: function(_s: PChar): integer; begin LibHandle := LoadLibrary('sample_dll.dll'); ShowMessage(IntToStr(CountChars('Hello world'))); // Access violation FreeLibrary(LibHandle); end; This is the DLL code: library sample_dll; uses FastMM4, FastMM4Messages, SysUtils, Classes; {$R *.res} function CountChars(_s: PChar): integer; stdcall; begin Result := Length(_s); end; exports CountChars; begin end.

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• [C]Dynamic allocation memory of structure, related to GTK

  - by MakeItWork

  Hello, I have following structure: typedef struct { GtkWidget* PoziomaLinijka; GtkWidget* PionowaLinijka; GtkWidget* Label1; GtkWidget* Label2; gint x,y; } StrukturaDrawing; And i need to allocate it on the heap because later I have functions which uses that structure and I don't want to use global variables. So I allocate it like this: StrukturaDrawing* Wsk; Wsk = (StrukturaDrawing*)malloc(sizeof(StrukturaDrawing)); if (!Wsk) { printf("Error\n"); } And it doesn't returning error and also works great with other functions, it works the way I wanted it to work so finally i wanted to free that memory and here is problem because in Debug Mode compilator bitches: First-chance exception at 0x102d12b4 in GTK.exe: 0xC0000005: Access violation reading location 0xfffffffc. Unhandled exception at 0x102d12b4 in GTK.exe: 0xC0000005: Access violation reading location 0xfffffffc. I connect callback to my function, like that: g_signal_connect(G_OBJECT(Okno), "destroy", G_CALLBACK(Wyjscie), Wsk); Function which is suppose to free memory and close program: void Wyjscie(GtkWindow* window, GdkEvent* event, StrukturaDrawing* data) { gtk_main_quit(); free(data); data = NULL; } Any help really appreciated.

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• Postgresql has broken apt-get on Ubuntu

  - by Raphie Palefsky-Smith

  On ubuntu 12.04, whenever I try to install a package using apt-get I'm greeted by: The following packages have unmet dependencies: postgresql-9.1 : Depends: postgresql-client-9.1 but it is not going to be instal led E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a so lution). apt-get install postgresql-client-9.1 generates: The following packages have unmet dependencies: postgresql-client-9.1 : Breaks: postgresql-9.1 (< 9.1.6-0ubuntu12.04.1) but 9.1.3-2 is to be installed apt-get -f install and apt-get remove postgresql-9.1 both give: Removing postgresql-9.1 ... * Stopping PostgreSQL 9.1 database server * Error: /var/lib/postgresql/9.1/main is not accessible or does not exist ...fail! invoke-rc.d: initscript postgresql, action "stop" failed. dpkg: error processing postgresql-9.1 (--remove): subprocess installed pre-removal script returned error exit status 1 Errors were encountered while processing: postgresql-9.1 E: Sub-process /usr/bin/dpkg returned an error code (1) So, apt-get is crippled, and I can't find a way out. Is there any way to resolve this without a re-install? EDIT: apt-cache show postgresql-9.1 returns: Package: postgresql-9.1 Priority: optional Section: database Installed-Size: 11164 Maintainer: Ubuntu Developers <[email protected]> Original-Maintainer: Martin Pitt <[email protected]> Architecture: amd64 Version: 9.1.6-0ubuntu12.04.1 Replaces: postgresql-contrib-9.1 (<< 9.1~beta1-3~), postgresql-plpython-9.1 (<< 9.1.6-0ubuntu12.04.1) Depends: libc6 (>= 2.15), libcomerr2 (>= 1.01), libgssapi-krb5-2 (>= 1.8+dfsg), libkrb5-3 (>= 1.6.dfsg.2), libldap-2.4-2 (>= 2.4.7), libpam0g (>= 0.99.7.1), libpq5 (>= 9.1~), libssl1.0.0 (>= 1.0.0), libxml2 (>= 2.7.4), postgresql-client-9.1, postgresql-common (>= 115~), tzdata, ssl-cert, locales Suggests: oidentd | ident-server, locales-all Conflicts: postgresql (<< 7.5) Breaks: postgresql-plpython-9.1 (<< 9.1.6-0ubuntu12.04.1) Filename: pool/main/p/postgresql-9.1/postgresql-9.1_9.1.6-0ubuntu12.04.1_amd64.deb Size: 4298270 MD5sum: 9ee2ab5f25f949121f736ad80d735d57 SHA1: 5eac1cca8d00c4aec4fb55c46fc2a013bc401642 SHA256: 4e6c24c251a01f1b6a340c96d24fdbb92b5e2f8a2f4a8b6b08a0df0fe4cf62ab Description-en: object-relational SQL database, version 9.1 server PostgreSQL is a fully featured object-relational database management system. It supports a large part of the SQL standard and is designed to be extensible by users in many aspects. Some of the features are: ACID transactions, foreign keys, views, sequences, subqueries, triggers, user-defined types and functions, outer joins, multiversion concurrency control. Graphical user interfaces and bindings for many programming languages are available as well. . This package provides the database server for PostgreSQL 9.1. Servers for other major release versions can be installed simultaneously and are coordinated by the postgresql-common package. A package providing ident-server is needed if you want to authenticate remote connections with identd. Homepage: http://www.postgresql.org/ Description-md5: c487fe4e86f0eac09ed9847282436059 Bugs: https://bugs.launchpad.net/ubuntu/+filebug Origin: Ubuntu Supported: 5y Task: postgresql-server Package: postgresql-9.1 Priority: optional Section: database Installed-Size: 11164 Maintainer: Ubuntu Developers <[email protected]> Original-Maintainer: Martin Pitt <[email protected]> Architecture: amd64 Version: 9.1.5-0ubuntu12.04 Replaces: postgresql-contrib-9.1 (<< 9.1~beta1-3~), postgresql-plpython-9.1 (<< 9.1.5-0ubuntu12.04) Depends: libc6 (>= 2.15), libcomerr2 (>= 1.01), libgssapi-krb5-2 (>= 1.8+dfsg), libkrb5-3 (>= 1.6.dfsg.2), libldap-2.4-2 (>= 2.4.7), libpam0g (>= 0.99.7.1), libpq5 (>= 9.1~), libssl1.0.0 (>= 1.0.0), libxml2 (>= 2.7.4), postgresql-client-9.1, postgresql-common (>= 115~), tzdata, ssl-cert, locales Suggests: oidentd | ident-server, locales-all Conflicts: postgresql (<< 7.5) Breaks: postgresql-plpython-9.1 (<< 9.1.5-0ubuntu12.04) Filename: pool/main/p/postgresql-9.1/postgresql-9.1_9.1.5-0ubuntu12.04_amd64.deb Size: 4298028 MD5sum: 3797b030ca8558a67b58e62cc0a22646 SHA1: ad340a9693341621b82b7f91725fda781781c0fb SHA256: 99aa892971976b85bcf6fb2e1bb8bf3e3fb860190679a225e7ceeb8f33f0e84b Description-en: object-relational SQL database, version 9.1 server PostgreSQL is a fully featured object-relational database management system. It supports a large part of the SQL standard and is designed to be extensible by users in many aspects. Some of the features are: ACID transactions, foreign keys, views, sequences, subqueries, triggers, user-defined types and functions, outer joins, multiversion concurrency control. Graphical user interfaces and bindings for many programming languages are available as well. . This package provides the database server for PostgreSQL 9.1. Servers for other major release versions can be installed simultaneously and are coordinated by the postgresql-common package. A package providing ident-server is needed if you want to authenticate remote connections with identd. Homepage: http://www.postgresql.org/ Description-md5: c487fe4e86f0eac09ed9847282436059 Bugs: https://bugs.launchpad.net/ubuntu/+filebug Origin: Ubuntu Supported: 5y Task: postgresql-server Package: postgresql-9.1 Priority: optional Section: database Installed-Size: 11220 Maintainer: Martin Pitt <[email protected]> Original-Maintainer: Martin Pitt <[email protected]> Architecture: amd64 Version: 9.1.3-2 Replaces: postgresql-contrib-9.1 (<< 9.1~beta1-3~), postgresql-plpython-9.1 (<< 9.1.3-2) Depends: libc6 (>= 2.15), libcomerr2 (>= 1.01), libgssapi-krb5-2 (>= 1.8+dfsg), libkrb5-3 (>= 1.6.dfsg.2), libldap-2.4-2 (>= 2.4.7), libpam0g (>= 0.99.7.1), libpq5 (>= 9.1~), libssl1.0.0 (>= 1.0.0), libxml2 (>= 2.7.4), postgresql-client-9.1, postgresql-common (>= 115~), tzdata, ssl-cert, locales Suggests: oidentd | ident-server, locales-all Conflicts: postgresql (<< 7.5) Breaks: postgresql-plpython-9.1 (<< 9.1.3-2) Filename: pool/main/p/postgresql-9.1/postgresql-9.1_9.1.3-2_amd64.deb Size: 4284744 MD5sum: bad9aac349051fe86fd1c1f628797122 SHA1: a3f5d6583cc6e2372a077d7c2fc7adfcfa0d504d SHA256: e885c32950f09db7498c90e12c4d1df0525038d6feb2f83e2e50f563fdde404a Description-en: object-relational SQL database, version 9.1 server PostgreSQL is a fully featured object-relational database management system. It supports a large part of the SQL standard and is designed to be extensible by users in many aspects. Some of the features are: ACID transactions, foreign keys, views, sequences, subqueries, triggers, user-defined types and functions, outer joins, multiversion concurrency control. Graphical user interfaces and bindings for many programming languages are available as well. . This package provides the database server for PostgreSQL 9.1. Servers for other major release versions can be installed simultaneously and are coordinated by the postgresql-common package. A package providing ident-server is needed if you want to authenticate remote connections with identd. Homepage: http://www.postgresql.org/ Description-md5: c487fe4e86f0eac09ed9847282436059 Bugs: https://bugs.launchpad.net/ubuntu/+filebug Origin: Ubuntu Supported: 5y Task: postgresql-server

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• How do you find what process is holding a file open in Windows?

  - by cletus

  One thing that annoys me no end about Windows is the old "sharing violation" error. Often you can't identify what's holding it open. Usually it's just an editor or explorer just pointing to a relevant directory but sometimes I've had to resort to rebooting my machine. Any suggestions on how to find the culprit?

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• What is the right tool to detect VMT or heap corruption in Delphi ?

  - by Roland Bengtsson

  I'm a member in a team that use Delphi 2007 for a larger application and we suspect heap corruption because sometimes there are strange bugs that have no other explanation. I believe that the Rangechecking option for the compiler is only for arrays. I want a tool that give an exception or log when there is a write on a memory address that is not allocated by the application. Regards EDIT: The error is of type: Error: Access violation at address 00404E78 in module 'BoatLogisticsAMCAttracsServer.exe'. Read of address FFFFFFDD EDIT2: Thanks for all suggestions. Unfortunately I think that the solution is deeper than that. We use a patched version of Bold for Delphi as we own the source. Probably there are some errors introduced in the Bold framwork. Yes we have a log with callstacks that are handled by JCL and also trace messages. So a callstack with the exception can lock like this: 20091210 16:02:29 (2356) [EXCEPTION] Raised EBold: Failed to derive ServerSession.mayDropSession: Boolean OCL expression: not active and not idle and timeout and (ApplicationKernel.allinstances->first.CurrentSession <> self) Error: Access violation at address 00404E78 in module 'BoatLogisticsAMCAttracsServer.exe'. Read of address FFFFFFDD. At Location BoldSystem.TBoldMember.CalculateDerivedMemberWithExpression (BoldSystem.pas:4016) Inner Exception Raised EBold: Failed to derive ServerSession.mayDropSession: Boolean OCL expression: not active and not idle and timeout and (ApplicationKernel.allinstances->first.CurrentSession <> self) Error: Access violation at address 00404E78 in module 'BoatLogisticsAMCAttracsServer.exe'. Read of address FFFFFFDD. At Location BoldSystem.TBoldMember.CalculateDerivedMemberWithExpression (BoldSystem.pas:4016) Inner Exception Call Stack: [00] System.TObject.InheritsFrom (sys\system.pas:9237) Call Stack: [00] BoldSystem.TBoldMember.CalculateDerivedMemberWithExpression (BoldSystem.pas:4016) [01] BoldSystem.TBoldMember.DeriveMember (BoldSystem.pas:3846) [02] BoldSystem.TBoldMemberDeriver.DoDeriveAndSubscribe (BoldSystem.pas:7491) [03] BoldDeriver.TBoldAbstractDeriver.DeriveAndSubscribe (BoldDeriver.pas:180) [04] BoldDeriver.TBoldAbstractDeriver.SetDeriverState (BoldDeriver.pas:262) [05] BoldDeriver.TBoldAbstractDeriver.Derive (BoldDeriver.pas:117) [06] BoldDeriver.TBoldAbstractDeriver.EnsureCurrent (BoldDeriver.pas:196) [07] BoldSystem.TBoldMember.EnsureContentsCurrent (BoldSystem.pas:4245) [08] BoldSystem.TBoldAttribute.EnsureNotNull (BoldSystem.pas:4813) [09] BoldAttributes.TBABoolean.GetAsBoolean (BoldAttributes.pas:3069) [10] BusinessClasses.TLogonSession._GetMayDropSession (code\BusinessClasses.pas:31854) [11] DMAttracsTimers.TAttracsTimerDataModule.RemoveDanglingLogonSessions (code\DMAttracsTimers.pas:237) [12] DMAttracsTimers.TAttracsTimerDataModule.UpdateServerTimeOnTimerTrig (code\DMAttracsTimers.pas:482) [13] DMAttracsTimers.TAttracsTimerDataModule.TimerKernelWork (code\DMAttracsTimers.pas:551) [14] DMAttracsTimers.TAttracsTimerDataModule.AttracsTimerTimer (code\DMAttracsTimers.pas:600) [15] ExtCtrls.TTimer.Timer (ExtCtrls.pas:2281) [16] Classes.StdWndProc (common\Classes.pas:11583) The inner exception part is the callstack at the moment an exception is reraised. EDIT3: The theory right now is that the Virtual Memory Table (VMT) is somehow broken. When this happen there is no indication of it. Only when a method is called an exception is raised (ALWAYS on address FFFFFFDD, -35 decimal) but then it is too late. You don't know the real cause for the error. Any hint of how to catch a bug like this is really appreciated!!! We have tried with SafeMM, but the problem is that the memory consumption is too high even when the 3 GB flag is used. So now I try to give a bounty to the SO community :) EDIT4: One hint is that according the log there is often (or even always) another exception before this. It can be for example optimistic locking in the database. We have tried to raise exceptions by force but in test environment it just works fine. EDIT5: Story continues... I did a search on the logs for the last 30 days now. The result: "Read of address FFFFFFDB" 0 "Read of address FFFFFFDC" 24 "Read of address FFFFFFDD" 270 "Read of address FFFFFFDE" 22 "Read of address FFFFFFDF" 7 "Read of address FFFFFFE0" 20 "Read of address FFFFFFE1" 0 So the current theory is that an enum (there is a lots in Bold) overwrite a pointer. I got 5 hits with different address above. It could mean that the enum holds 5 values where the second one is most used. If there is an exception a rollback should occur for the database and Boldobjects should be destroyed. Maybe there is a chance that not everything is destroyed and a enum still can write to an address location. If this is true maybe it is possible to search the code by a regexpr for an enum with 5 values ? EDIT6: To summarize, no there is no solution to the problem yet. I realize that I may mislead you a bit with the callstack. Yes there are a timer in that but there are other callstacks without a timer. Sorry for that. But there are 2 common factors. An exception with Read of address FFFFFFxx. Top of callstack is System.TObject.InheritsFrom (sys\system.pas:9237) This convince me that VilleK best describe the problem. I'm also convinced that the problem is somewhere in the Bold framework. But the BIG question is, how can problems like this be solved ? It is not enough to have an Assert like VilleK suggest as the damage has already happened and the callstack is gone at that moment. So to describe my view of what may cause the error: Somewhere a pointer is assigned a bad value 1, but it can be also 0, 2, 3 etc. An object is assigned to that pointer. There is method call in the objects baseclass. This cause method TObject.InheritsForm to be called and an exception appear on address FFFFFFDD. Those 3 events can be together in the code but they may also be used much later. I think this is true for the last method call. EDIT7: We work closely with the the author of Bold Jan Norden and he recently found a bug in the OCL-evaluator in Bold framework. When this was fixed these kinds of exceptions decreased a lot but they still occasionally come. But it is a big relief that this is almost solved.

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• Parallelism in .NET – Part 13, Introducing the Task class

  - by Reed

  Once we’ve used a task-based decomposition to decompose a problem, we need a clean abstraction usable to implement the resulting decomposition.  Given that task decomposition is founded upon defining discrete tasks, .NET 4 has introduced a new API for dealing with task related issues, the aptly named Task class. The Task class is a wrapper for a delegate representing a single, discrete task within your decomposition.  We will go into various methods of construction for tasks later, but, when reduced to its fundamentals, an instance of a Task is nothing more than a wrapper around a delegate with some utility functionality added.  In order to fully understand the Task class within the new Task Parallel Library, it is important to realize that a task really is just a delegate – nothing more.  In particular, note that I never mentioned threading or parallelism in my description of a Task.  Although the Task class exists in the new System.Threading.Tasks namespace: Tasks are not directly related to threads or multithreading. Of course, Task instances will typically be used in our implementation of concurrency within an application, but the Task class itself does not provide the concurrency used.  The Task API supports using Tasks in an entirely single threaded, synchronous manner. Tasks are very much like standard delegates.  You can execute a task synchronously via Task.RunSynchronously(), or you can use Task.Start() to schedule a task to run, typically asynchronously.  This is very similar to using delegate.Invoke to execute a delegate synchronously, or using delegate.BeginInvoke to execute it asynchronously. The Task class adds some nice functionality on top of a standard delegate which improves usability in both synchronous and multithreaded environments. The first addition provided by Task is a means of handling cancellation via the new unified cancellation mechanism of .NET 4.  If the wrapped delegate within a Task raises an OperationCanceledException during it’s operation, which is typically generated via calling ThrowIfCancellationRequested on a CancellationToken, or if the CancellationToken used to construct a Task instance is flagged as canceled, the Task’s IsCanceled property will be set to true automatically.  This provides a clean way to determine whether a Task has been canceled, often without requiring specific exception handling. Tasks also provide a clean API which can be used for waiting on a task.  Although the Task class explicitly implements IAsyncResult, Tasks provide a nicer usage model than the traditional .NET Asynchronous Programming Model.  Instead of needing to track an IAsyncResult handle, you can just directly call Task.Wait() to block until a Task has completed.  Overloads exist for providing a timeout, a CancellationToken, or both to prevent waiting indefinitely.  In addition, the Task class provides static methods for waiting on multiple tasks – Task.WaitAll and Task.WaitAny, again with overloads providing time out options.  This provides a very simple, clean API for waiting on single or multiple tasks. Finally, Tasks provide a much nicer model for Exception handling.  If the delegate wrapped within a Task raises an exception, the exception will automatically get wrapped into an AggregateException and exposed via the Task.Exception property.  This exception is stored with the Task directly, and does not tear down the application.  Later, when Task.Wait() (or Task.WaitAll or Task.WaitAny) is called on this task, an AggregateException will be raised at that point if any of the tasks raised an exception.  For example, suppose we have the following code: Task taskOne = new Task( () => { throw new ApplicationException("Random Exception!"); }); Task taskTwo = new Task( () => { throw new ArgumentException("Different exception here"); }); // Start the tasks taskOne.Start(); taskTwo.Start(); try { Task.WaitAll(new[] { taskOne, taskTwo }); } catch (AggregateException e) { Console.WriteLine(e.InnerExceptions.Count); foreach (var inner in e.InnerExceptions) Console.WriteLine(inner.Message); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Here, our routine will print: 2 Different exception here Random Exception! Note that we had two separate tasks, each of which raised two distinctly different types of exceptions.  We can handle this cleanly, with very little code, in a much nicer manner than the Asynchronous Programming API.  We no longer need to handle TargetInvocationException or worry about implementing the Event-based Asynchronous Pattern properly by setting the AsyncCompletedEventArgs.Error property.  Instead, we just raise our exception as normal, and handle AggregateException in a single location in our calling code.

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• New on the Java Channel: Low-Latency Applications, JavaFX on Raspberry PI, and more

  - by terrencebarr

  If you haven’t checked out the Java YouTube channel lately … here is some of the stuff you’re missing: Understanding the JVM and Low Latency Applications (picture) JavaFX on the Raspberry Pi 55 New Java 7 Features: Part 3 – Concurrency Properties and Binding with JavaFX 2 Intro And something fun & cool: Java @ Maker Faire 2012 Much more on the Java Channel. Enjoy! Cheers, – Terrence Filed under: Mobile & Embedded Tagged: Embedded Java, Java 7, Java Channel, Java Embedded, JavaFX, Maker Faire, Raspberry Pi, video, webcast, YouTube

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• Google I/O 2010 - Go Programming

  Google I/O 2010 - Go Programming Google I/O 2010 - Go Programming Tech Talks Rob Pike, Russ Cox The Go Programming Language was released as an open source project in late 2009. This session will illustrate how programming in Go differs from other languages through a set of examples demonstrating features particular to Go. These include concurrency, embedded types, methods on any type, and program construction using interfaces. Very little time will be spent waiting for compilation. For all I/O 2010 sessions, please go to code.google.com From: GoogleDevelopers Views: 12 0 ratings Time: 56:11 More in Science & Technology

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• Getting around US law

  - by Anne Nonimus

  Hello. Let's suppose that someone is interested in starting a website that might be in violation of some US laws (such as copyright, gambling, pornography, etc.). I know this question isn't in the best taste, so I can understand if it is closed or deleted. Please consider, however, that not everything against US law is considered immoral or unethical to some people. I was reading how many online poker services are based in the Cayman Islands to get around US law. Are there other countries with good hosting services to avoid prosecution by US law? Many laws enforceable in the US are also enforceable in many other jurisdictions (copyright for one), so it would be interesting to know if there are safe havens for sensitive websites.

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• Windows Azure Use Case: Hybrid Applications

  - by BuckWoody

  This is one in a series of posts on when and where to use a distributed architecture design in your organization's computing needs. You can find the main post here: http://blogs.msdn.com/b/buckwoody/archive/2011/01/18/windows-azure-and-sql-azure-use-cases.aspx  Description: Organizations see the need for computing infrastructures that they can “rent” or pay for only when they need them. They also understand the benefits of distributed computing, but do not want to create this infrastructure themselves. However, they may have considerations that prevent them from moving all of their current IT investment to a distributed environment: Private data (do not want to send or store sensitive data off-site) High dollar investment in current infrastructure Applications currently running well, but may need additional periodic capacity Current applications not designed in a stateless fashion In these situations, a “hybrid” approach works best. In fact, with Windows Azure, a hybrid approach is an optimal way to implement distributed computing even when the stipulations above do not apply. Keeping a majority of the computing function in an organization local while exploring and expanding that footprint into Windows and SQL Azure is a good migration or expansion strategy. A “hybrid” architecture merely means that part of a computing cycle is shared between two architectures. For instance, some level of computing might be done in a Windows Azure web-based application, while the data is stored locally at the organization. Implementation: There are multiple methods for implementing a hybrid architecture, in a spectrum from very little interaction from the local infrastructure to Windows or SQL Azure. The patterns fall into two broad schemas, and even these can be mixed. 1. Client-Centric Hybrid Patterns In this pattern, programs are coded such that the client system sends queries or compute requests to multiple systems. The “client” in this case might be a web-based codeset actually stored on another system (which acts as a client, the user’s device serving as the presentation layer) or a compiled program. In either case, the code on the client requestor carries the burden of defining the layout of the requests. While this pattern is often the easiest to code, it’s the most brittle. Any change in the architecture must be reflected on each client, but this can be mitigated by using a centralized system as the client such as in the web scenario. 2. System-Centric Hybrid Patterns Another approach is to create a distributed architecture by turning on-site systems into “services” that can be called from Windows Azure using the service Bus or the Access Control Services (ACS) capabilities. Code calls from a series of in-process client application. In this pattern you move the “client” interface into the server application logic. If you do not wish to change the application itself, you can “layer” the results of the code return using a product (such as Microsoft BizTalk) that exposes a Web Services Definition Language (WSDL) endpoint to Windows Azure using the Application Fabric. In effect, this is similar to creating a Service Oriented Architecture (SOA) environment, and has the advantage of de-coupling your computing architecture. If each system offers a “service” of the results of some software processing, the operating system or platform becomes immaterial, assuming it adheres to a service contract. There are important considerations when you federate a system, whether to Windows or SQL Azure or any other distributed architecture. While these considerations are consistent with coding any application for distributed computing, they are especially important for a hybrid application. Connection resiliency - Applications on-premise normally have low-latency and good connection properties, something you’re not always guaranteed in a distributed and hybrid application. Whether a centralized client or a distributed one, the code should be able to handle extended retry logic. Authorization and Access - In a single authorization environment like a Active Directory domain, security is handled at a user-password level. In a distributed computing environment, you have more options. You can mitigate this with  using The Windows Azure Application Fabric feature of ACS to make the Azure application aware of the App Fabric as an ADFS provider. However, a claims-based authentication structure is often a superior choice.  Consistency and Concurrency - When you have a Relational Database Management System (RDBMS), Consistency and Concurrency are part of the design. In a Service Architecture, you need to plan for sequential message handling and lifecycle. Resources: How to Build a Hybrid On-Premise/In Cloud Application: http://blogs.msdn.com/b/ignitionshowcase/archive/2010/11/09/how-to-build-a-hybrid-on-premise-in-cloud-application.aspx  General Architecture guidance: http://blogs.msdn.com/b/buckwoody/archive/2010/12/21/windows-azure-learning-plan-architecture.aspx   

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• Oracle demande 211 millions de dollars de plus à SAP au titre des intérêts des 1,3 milliards du verdict de l'affaire TomorrowNow

  Oracle demande 211 millions de dollars supplémentaires à SAP Au titre des intérêts des 1,3 milliards du verdict de l'affaire TomorrowNow Mise à jour du 13/12/10 Chez Oracle, un sou est un sou. SAP le savait déjà, mais l'éditeur Allemand en a aujourd'hui la confirmation. Condamné à verser la somme record de 1,3 milliards de dollars à Oracle dans l'affaire TomorrowNow, sur fond de violation de copyright, d'espionnage industriel et de démarchage illégal de clientèle (lire ci-avant), SAP risque de devoir remettre la main à son porte-monnaie. Oracle lui réclame en effet 211 millions supplémentaires au titre des intérêts des 1,3 mil...

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• The way I think about Diagnostic tools

  - by Daniel Moth

  Every software has issues, or as we like to call them "bugs". That is not a discussion point, just a mere fact. It follows that an important skill for developers is to be able to diagnose issues in their code. Of course we need to advance our tools and techniques so we can prevent bugs getting into the code (e.g. unit testing), but beyond designing great software, diagnosing bugs is an equally important skill. To diagnose issues, the most important assets are good techniques, skill, experience, and maybe talent. What also helps is having good diagnostic tools and what helps further is knowing all the features that they offer and how to use them. The following classification is how I like to think of diagnostics. Note that like with any attempt to bucketize anything, you run into overlapping areas and blurry lines. Nevertheless, I will continue sharing my generalizations ;-) It is important to identify at the outset if you are dealing with a performance or a correctness issue. If you have a performance issue, use a profiler. I hear people saying "I am using the debugger to debug a performance issue", and that is fine, but do know that a dedicated profiler is the tool for that job. Just because you don't need them all the time and typically they cost more plus you are not as familiar with them as you are with the debugger, doesn't mean you shouldn't invest in one and instead try to exclusively use the wrong tool for the job. Visual Studio has a profiler and a concurrency visualizer (for profiling multi-threaded apps). If you have a correctness issue, then you have several options - that's next :-) This is how I think of identifying a correctness issue Do you want a tool to find the issue for you at design time? The compiler is such a tool - it gives you an exact list of errors. Compilers now also offer warnings, which is their way of saying "this may be an error, but I am not smart enough to know for sure". There are also static analysis tools, which go a step further than the compiler in identifying issues in your code, sometimes with the aid of code annotations and other times just by pointing them at your raw source. An example is FxCop and much more in Visual Studio 11 Code Analysis. Do you want a tool to find the issue for you with code execution? Just like static tools, there are also dynamic analysis tools that instead of statically analyzing your code, they analyze what your code does dynamically at runtime. Whether you have to setup some unit tests to invoke your code at runtime, or have to manually run your app (and interact with it) under the tool, or have to use a script to execute your binary under the tool… that varies. The result is still a list of issues for you to address after the analysis is complete or a pause of the execution when the first issue is encountered. If a code path was not taken, no analysis for it will exist, obviously. An example is the GPU Race detection tool that I'll be talking about on the C++ AMP team blog. Another example is the MSR concurrency CHESS tool. Do you want you to find the issue at design time using a tool? Perform a code walkthrough on your own or with colleagues. There are code review tools that go beyond just diffing sources, and they help you with that aspect too. For example, there is a new one in Visual Studio 11 and searching with my favorite search engine yielded this article based on the Developer Preview. Do you want you to find the issue with code execution? Use a debugger - let’s break this down further next. This is how I think of debugging: There is post mortem debugging. That means your code has executed and you did something in order to examine what happened during its execution. This can vary from manual printf and other tracing statements to trace events (e.g. ETW) to taking dumps. In all cases, you are left with some artifact that you examine after the fact (after code execution) to discern what took place hoping it will help you find the bug. Learn how to debug dump files in Visual Studio. There is live debugging. I will elaborate on this in a separate post, but this is where you inspect the state of your program during its execution, and try to find what the problem is. More from me in a separate post on live debugging. There is a hybrid of live plus post-mortem debugging. This is for example what tools like IntelliTrace offer. If you are a tools vendor interested in the diagnostics space, it helps to understand where in the above classification your tool excels, where its primary strength is, so you can market it as such. Then it helps to see which of the other areas above your tool touches on, and how you can make it even better there. Finally, see what areas your tool doesn't help at all with, and evaluate whether it should or continue to stay clear. Even though the classification helps us think about this space, the reality is that the best tools are either extremely excellent in only one of this areas, or more often very good across a number of them. Another approach is to offer a toolset covering all areas, with appropriate integration and hand off points from one to the other. Anyway, with that brain dump out of the way, in follow-up posts I will dive into live debugging, and specifically live debugging in Visual Studio - stay tuned if that interests you. Comments about this post by Daniel Moth welcome at the original blog.

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• Google I/O 2011: Large-scale Data Analysis Using the App Engine Pipeline API

  Google I/O 2011: Large-scale Data Analysis Using the App Engine Pipeline API Brett Slatkin The Pipeline API makes it easy to analyze complex data using App Engine. This talk will cover how to build multi-phase Map Reduce workflows; how to merge multiple large data sources with "join" operations; and how to build reusable analysis components. It will also cover the API's concurrency model, how to debug in production, and built-in testing facilities. From: GoogleDevelopers Views: 3320 17 ratings Time: 51:39 More in Science & Technology

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• What is the meaning of the sentence "we wanted it to be compiled so it’s not burning CPU doing the wrong stuff."

  - by user2434

  I was reading this article. It has the following paragraph. And did Scala turn out to be fast? Well, what’s your definition of fast? About as fast as Java. It doesn’t have to be as fast as C or Assembly. Python is not significantly faster than Ruby. We wanted to do more with fewer machines, taking better advantage of concurrency; we wanted it to be compiled so it’s not burning CPU doing the wrong stuff. I am looking for the meaning of the last sentence. How will interpreted language make the CPU do "wrong" stuff ?

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• Am I allowed to display a small image on top of a Google Maps Static Api map?

  - by Fábio Santos

  I am the webmaster to my company's website. I was asked to make the Google Map on this page smaller, but the interactive map doesn't work well at all at 300x200. I was asked to place a screenshot there but since that seems to be a violation of Google's terms I decided to use the Static Maps API. As you can see, on the page, I have a custom pointer icon. I don't want to lose it, so I intend to use HTML and CSS to place the pointer over the map, thus replacing the original pointer on the client side. Am I allowed to do that?

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• MySQL Connect Only 10 Days Away - Focus on InnoDB Sessions

  - by Bertrand Matthelié

  Time flies and MySQL Connect is only 10 days away! You can check out the full program here as well as in the September edition of the MySQL newsletter. Mat recently blogged about the MySQL Cluster sessions you’ll have the opportunity to attend, and below are those focused on InnoDB. Remember you can plan your schedule with Schedule Builder. Saturday, 1.00 pm, Room Golden Gate 3: 10 Things You Should Know About InnoDB—Calvin Sun, Oracle InnoDB is the default storage engine for Oracle’s MySQL as of MySQL Release 5.5. It provides the standard ACID-compliant transactions, row-level locking, multiversion concurrency control, and referential integrity. InnoDB also implements several innovative technologies to improve its performance and reliability. This presentation gives a brief history of InnoDB; its main features; and some recent enhancements for better performance, scalability, and availability. Saturday, 5.30 pm, Room Golden Gate 4: Demystified MySQL/InnoDB Performance Tuning—Dimitri Kravtchuk, Oracle This session covers performance tuning with MySQL and the InnoDB storage engine for MySQL and explains the main improvements made in MySQL Release 5.5 and Release 5.6. Which setting for which workload? Which value will be better for my system? How can I avoid potential bottlenecks from the beginning? Do I need a purge thread? Is it true that InnoDB doesn't need thread concurrency anymore? These and many other questions are asked by DBAs and developers. Things are changing quickly and constantly, and there is no “silver bullet.” But understanding the configuration setting’s impact is already a huge step in performance improvement. Bring your ideas and problems to share them with others—the discussion is open, just moderated by a speaker. Sunday, 10.15 am, Room Golden Gate 4: Better Availability with InnoDB Online Operations—Calvin Sun, Oracle Many top Web properties rely on Oracle’s MySQL as a critical piece of infrastructure for serving millions of users. Database availability has become increasingly important. One way to enhance availability is to give users full access to the database during data definition language (DDL) operations. The online DDL operations in recent MySQL releases offer users the flexibility to perform schema changes while having full access to the database—that is, with minimal delay of operations on a table and without rebuilding the entire table. These enhancements provide better responsiveness and availability in busy production environments. This session covers these improvements in the InnoDB storage engine for MySQL for online DDL operations such as add index, drop foreign key, and rename column. Sunday, 11.45 am, Room Golden Gate 7: Developing High-Throughput Services with NoSQL APIs to InnoDB and MySQL Cluster—Andrew Morgan and John Duncan, Oracle Ever-increasing performance demands of Web-based services have generated significant interest in providing NoSQL access methods to MySQL (MySQL Cluster and the InnoDB storage engine of MySQL), enabling users to maintain all the advantages of their existing relational databases while providing blazing-fast performance for simple queries. Get the best of both worlds: persistence; consistency; rich SQL queries; high availability; scalability; and simple, flexible APIs and schemas for agile development. This session describes the memcached connectors and examines some use cases for how MySQL and memcached fit together in application architectures. It does the same for the newest MySQL Cluster native connector, an easy-to-use, fully asynchronous connector for Node.js. Sunday, 1.15 pm, Room Golden Gate 4: InnoDB Performance Tuning—Inaam Rana, Oracle The InnoDB storage engine has always been highly efficient and includes many unique architectural elements to ensure high performance and scalability. In MySQL 5.5 and MySQL 5.6, InnoDB includes many new features that take better advantage of recent advances in operating systems and hardware platforms than previous releases did. This session describes unique InnoDB architectural elements for performance, new features, and how to tune InnoDB to achieve better performance. Sunday, 4.15 pm, Room Golden Gate 3: InnoDB Compression for OLTP—Nizameddin Ordulu, Facebook and Inaam Rana, Oracle Data compression is an important capability of the InnoDB storage engine for Oracle’s MySQL. Compressed tables reduce the size of the database on disk, resulting in fewer reads and writes and better throughput by reducing the I/O workload. Facebook pushes the limit of InnoDB compression and has made several enhancements to InnoDB, making this technology ready for online transaction processing (OLTP). In this session, you will learn the fundamentals of InnoDB compression. You will also learn the enhancements the Facebook team has made to improve InnoDB compression, such as reducing compression failures, not logging compressed page images, and allowing changes of compression level. Not registered yet? You can still save US$ 300 over the on-site fee – Register Now!

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• PPL and TPL sessions on channel9

  - by Daniel Moth

  Back in June there was an internal conference in Redmond ("Engineering Forum") aimed at Microsoft engineers, and delivered by Microsoft engineers. I was asked to put together a track on Multi-Core development, so I picked 6 parallelism experts and we created 6 awesome sessions (we won the top spot in the Top 10 :-)). Two of the speakers kept the content fairly external-friendly, so we received permission to publish their recordings publicly. Enjoy (best to download the High Quality WMV): Don McCrady - Parallelism in C++ Using the Concurrency Runtime Stephen Toub - Implementing Parallel Patterns using .NET 4 To get notified on future videos on parallelism (or to browse the archive) stay tuned on this channel9 parallel computing feed. Comments about this post welcome at the original blog.

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• Links from UK TechDays 2010 sessions on Entity Framework, Parallel Programming and Azure

  - by Eric Nelson

  [I will do some longer posts around my sessions when I get back from holiday next week] Big thanks to all those who attended my 3 sessions at TechDays this week (April 13th and 14th, 2010). I really enjoyed both days and watched some great session – my personal fave being the Silverlight/Expression session by my friend and colleague Mike Taulty. The following links should help get you up and running on each of the technologies. Entity Framework 4 Entity Framework 4 Resources http://bit.ly/ef4resources Entity Framework Team Blog http://blogs.msdn.com/adonet Entity Framework Design Blog http://blogs.msdn.com/efdesign/ Parallel Programming Parallel Computing Developer Center http://msdn.com/concurrency Code samples http://code.msdn.microsoft.com/ParExtSamples Managed Team Blog http://blogs.msdn.com/pfxteam Tools Team Blog http://blogs.msdn.com/visualizeparallel My code samples http://gist.github.com/364522  And PDC 2009 session recordings to watch: Windows Azure Platform UK Site http://bit.ly/landazure UK Community http://bit.ly/ukazure (http://ukazure.ning.com ) Feedback www.mygreatwindowsazureidea.com Azure Diagnostics Manager - A client for Windows Azure Diagnostics Cloud Storage Studio - A client for Windows Azure Storage SQL Azure Migration Wizard http://sqlazuremw.codeplex.com

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• Android : Pourquoi Apple n'attaque-t-il pas directement Google ? Eric Schmidt étonné que la firme vise plutôt les constructeurs

  Android : Pourquoi Apple n'attaque-t-il pas directement Google ? Eric Schmidt étonné que la firme vise plutôt les constructeurs Dans un entretien accordé au magazine Wall Street Journal concernant les relations tendues entre Google et Apple, Eric Schmidt, Président du conseil d'administration de Google, exprime son étonnement au fait qu'Apple n'attaque pas directement Google en justice pour violation de brevets. La firme à la pomme croquée depuis plusieurs années est en conflit avec les constructeurs de terminaux Android, qu'elle accuse de violer dans leurs dispositifs ses propriétés intellectuelles. Dans sa dernière plainte contre Samsung, Apple s'attaque directement à l...

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• Links and code from session on Entity Framework 4, Parallel and C# 4.0 new features

  - by Eric Nelson

  Last week (12th May 2010) I did a session in the city on lot of the new .NET 4.0 Stuff. My demo code and links below. Code Parallel demos http://gist.github.com/364522  C# 4.0 new features http://gist.github.com/403826  EF4 Links Entity Framework 4 Resources http://bit.ly/ef4resources Entity Framework Team Blog http://blogs.msdn.com/adonet Entity Framework Design Blog http://blogs.msdn.com/efdesign/ Parallel Links Parallel Computing Dev Center http://msdn.com/concurrency Code samples http://code.msdn.microsoft.com/ParExtSamples Managed blog http://blogs.msdn.com/pfxteam Tools blog http://blogs.msdn.com/visualizeparallel C# 4.0 New features http://bit.ly/baq3aU  New in .NET 4.0 Coevolution http://bit.ly/axglst  New in C# 4.0 http://bit.ly/bG1U2Y

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• Web services, J2EE, Spring, DB integration project ideas - maybe data mining related?

  - by saral jain

  I am a graduate Computer Science student (Data Mining and Machine Learning) and have good exposure to core Java (3 years). I have read up on a bunch of stuff on the following topics: Design patterns, J2EE Web services (SOAP and REST), Spring, and Hibernate Java Concurrency - advanced features like Task and Executors. I would now like to do a project combining this stuff -- over my free time of course -- to get a better understanding of these things and to kind of make an end to end software (to learn the best design principles etc + SVN, maven). Any good project ideas would be really appreciated. I just want to build this stuff to learn, so I don't really mind re-inventing the wheel. Also, anything related to data mining would be an added bonus as it fits with my research but is absolutely not necessary since this project is more to learn to do large scale software development.

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