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• How do I unit test a finalizer?

  - by GraemeF

  I have the following class which is a decorator for an IDisposable object (I have omitted the stuff it adds) which itself implements IDisposable using a common pattern: public class DisposableDecorator : IDisposable { private readonly IDisposable _innerDisposable; public DisposableDecorator(IDisposable innerDisposable) { _innerDisposable = innerDisposable; } #region IDisposable Members public void Dispose() { Dispose(true); GC.SuppressFinalize(this); } #endregion ~DisposableDecorator() { Dispose(false); } protected virtual void Dispose(bool disposing) { if (disposing) _innerDisposable.Dispose(); } } I can easily test that innerDisposable is disposed when Dispose() is called: [Test] public void Dispose__DisposesInnerDisposable() { var mockInnerDisposable = new Mock<IDisposable>(); new DisposableDecorator(mockInnerDisposable.Object).Dispose(); mockInnerDisposable.Verify(x => x.Dispose()); } But how do I write a test to make sure innerDisposable does not get disposed by the finalizer? I want to write something like this but it fails, presumably because the finalizer hasn't been called by the GC thread: [Test] public void Finalizer__DoesNotDisposeInnerDisposable() { var mockInnerDisposable = new Mock<IDisposable>(); new DisposableDecorator(mockInnerDisposable.Object); GC.Collect(); mockInnerDisposable.Verify(x => x.Dispose(), Times.Never()); }

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• c# finalizer throwing exception?

  - by sjhuk

  Quote from MSDN: If Finalize or an override of Finalize throws an exception, the runtime ignores the exception, terminates that Finalize method, and continues the finalization process. Yet if I have: ~Person() { throw new Exception("meh"); } then it results in a runtime exception? p.s. I know that this should never happen, however I'm just curious around this behaviour. One of our clients had an empty try catch around all of their finalizers.. it didn't even log when things went wrong or reserect the object :/

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• .Net Finalizer Order / Semantics in Esent and Ravendb

  - by mattcodes

  Help me understand. I've read that "The time and order of execution of finalizers cannot be predicted or pre-determined" Correct? However looking at RavenDB source code TransactionStorage.cs I see this ~TransactionalStorage() { try { Trace.WriteLine( "Disposing esent resources from finalizer! You should call TransactionalStorage.Dispose() instead!"); Api.JetTerm2(instance, TermGrbit.Abrupt); } catch (Exception exception) { try { Trace.WriteLine("Failed to dispose esent instance from finalizer because: " + exception); } catch { } } } The API class (which belongs to Managed Esent) which presumable takes handles on native resources presumably using a SafeHandle? So if I understand correctly the native handles SafeHandle can be finalized before TransactionStorage which could have undesired effects, perhaps why Ayende has added an catch all clause around this? Actually diving into Esent code, it does not use SafeHandles. According to CLR via C# this is dangerous? internal static class SomeType { [DllImport("Kernel32", CharSet=CharSet.Unicode, EntryPoint="CreateEvent")] // This prototype is not robust private static extern IntPtr CreateEventBad( IntPtr pSecurityAttributes, Boolean manualReset, Boolean initialState, String name); // This prototype is robust [DllImport("Kernel32", CharSet=CharSet.Unicode, EntryPoint="CreateEvent")] private static extern SafeWaitHandle CreateEventGood( IntPtr pSecurityAttributes, Boolean manualReset, Boolean initialState, String name) public static void SomeMethod() { IntPtr handle = CreateEventBad(IntPtr.Zero, false, false, null); SafeWaitHandle swh = CreateEventGood(IntPtr.Zero, false, false, null); } } Managed Esent (NativeMEthods.cs) looks like this (using Ints vs IntPtrs?): [DllImport(EsentDll, CharSet = EsentCharSet, ExactSpelling = true)] public static extern int JetCreateDatabase(IntPtr sesid, string szFilename, string szConnect, out uint dbid, uint grbit); Is Managed Esent handling finalization/dispoal the correct way, and second is RavenDB handling finalizer the corret way or compensating for Managed Esent?

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• How do I handle all the exceptions in a C# class where both ctor and finalizer throw exceptions?

  - by Frank

  How can I handle all exceptions for a class similar to the following under certain circumstances? class Test : IDisposable { public Test() { throw new Exception("Exception in ctor"); } public void Dispose() { throw new Exception("Exception in Dispose()"); } ~Test() { this.Dispose(); } } I tried this but it doesn't work: static void Main() { Test t = null; try { t = new Test(); } catch (Exception ex) { Console.Error.WriteLine(ex.Message); } // t is still null } I have also tried to use "using" but it does not handle the exception thrown from ~Test(); static void Main() { try { using (Test t = new Test()) { } } catch (Exception ex) { Console.Error.WriteLine(ex.Message); } } Any ideas how can I work around?

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• Disposing a Bitmap through its Finalizer

  - by devoured elysium

  I have a complex program in which I have to first create, then use wrappers around bitmaps and send them across a lot of different classes. The problem in the end is deciding which classes should dispose the bitmaps. Most of the time the end classes don't know if they can indeed dispose the bitmap as the same bitmap can be used in several places. Also, I can't just copy the bitmaps because this is a kind of resource intensive algorithm and doing it would be dead slow. I looked up on reflector for Image/Bitmap's implementations and they seem to use the Dispose Pattern. So, even if I don't call Dispose(), the CLR will eventually call it some other time. Is it too bad if I just let the bitmaps be as they are, and let the finalizer take care of them?

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• Disposing underlying object from finalizer in an immutable object

  - by Juan Luis Soldi

  I'm trying to wrap around Awesomium and make it look to the rest of my code as close as possible to NET's WebBrowser since this is for an existing application that already uses the WebBrowser. In this library, there is a class called JSObject which represents a javascript object. You can get one of this, for instance, by calling the ExecuteJavascriptWithResult method of the WebView class. If you'd call it like myWebView.ExecuteJavascriptWithResult("document", string.Empty).ToObject(), then you'd get a JSObject that represents the document. I'm writing an immutable class (it's only field is a readonly JSObject object) called JSObjectWrap that wraps around JSObject which I want to use as base class for other classes that would emulate .NET classes such as HtmlElement and HtmlDocument. Now, these classes don't implement Dispose, but JSObject does. What I first thought was to call the underlying JSObject's Dispose method in my JSObjectWrap's finalizer (instead of having JSObjectWrap implement Dispose) so that the rest of my code can stay the way it is (instead of having to add using's everywhere and make sure every JSObjectWrap is being properly disposed). But I just realized if more than two JSObjectWrap's have the same underlying JSObject and one of them gets finalized this will mess up the other JSObjectWrap. So now I'm thinking maybe I should keep a static Dictionary of JSObjects and keep count of how many of each of them are being referenced by a JSObjectWrap but this sounds messy and I think could cause major performance issues. Since this sounds to me like a common pattern I wonder if anyone else has a better idea.

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• Are finalizers ever allowed to call other managed classes' methods?

  - by romkyns

  I used to be pretty sure the answer is "no", as explained in Overriding the Finalize method and Object.Finalize documentation. However, while randomly browsing through FileStream in Reflector, I found that it can actually call just such a method from a finalizer: private SafeFileHandle _handle; ~FileStream() { if (this._handle != null) { this.Dispose(false); } } protected override void Dispose(bool disposing) { try { ... } finally { if ((this._handle != null) && !this._handle.IsClosed) // <=== HERE { this._handle.Dispose(); // <=== AND HERE } [...] } } I started wondering whether this will always work due to the exact way in which it's written, and hence whether the "do not touch managed classes from finalizers" is just a guideline that can be broken given a good reason and the necessary knowledge to do it right. I dug a bit deeper and found out that the worst that can happen when the "rule" is broken is that the managed object being accessed had already been finalized, or may be getting finalized in parallel on a separate thread. So if the SafeFileHandle's finalizer didn't do anything that would cause a subsequent call to Dispose fail then the above should be fine... right? Question: so there might after all be situations in which a method on another managed class may be called reliably from a finalizer? I've always believed this to be false, but this code suggests that it's possible and that there can be good enough reasons to do it. Bonus: Observe that the SafeFileHandle will not even know it's being called from a finalizer, since this is just a normal call to Dispose(). The base class, SafeHandle, actually has two private methods, InternalDispose and InternalFinalize, and in this case InternalDispose will be called. Isn't this a problem? Why not?...

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• Why "Finalize method should not reference any other objects" ?

  - by mishal153

  I have been pondering why it is recommended that we should not release managed resources inside finalize. If you see the code example at http://msdn.microsoft.com/en-us/library/system.gc.suppressfinalize.aspx , and search for string "Dispose(bool disposing) executes in two distinct scenarios" and read that comment, you will understand what I mean. Only possibility I can think of is that it probably has something to do with the fact that it is not possible to predict when finalizer will get called. Does anyone know the right answer ? thanks, mishal

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• Performance implications of finalizers on JVM

  - by Alexey Romanov

  According to this post, in .Net, Finalizers are actually even worse than that. Besides that they run late (which is indeed a serious problem for many kinds of resources), they are also less powerful because they can only perform a subset of the operations allowed in a destructor (e.g., a finalizer cannot reliably use other objects, whereas a destructor can), and even when writing in that subset finalizers are extremely difficult to write correctly. And collecting finalizable objects is expensive: Each finalizable object, and the potentially huge graph of objects reachable from it, is promoted to the next GC generation, which makes it more expensive to collect by some large multiple. Does this also apply to JVMs in general and to HotSpot in particular?

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• Measuring the time to create and destroy a simple object

  - by portoalet

  From Effective Java 2nd Edition Item 7: Avoid Finalizers "Oh, and one more thing: there is a severe performance penalty for using finalizers. On my machine, the time to create and destroy a simple object is about 5.6 ns. Adding a finalizer increases the time to 2,400 ns. In other words, it is about 430 times slower to create and destroy objects with finalizers." How can one measure the time to create and destroy an object? Do you just do: long start = System.nanoTime(); SimpleObject simpleObj = new SimpleObject(); simpleObj.finalize(); long end = System.nanoTime(); long time = end - start;

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• Can I detect whether an object has called GC.SuppressFinalize?

  - by Joe White

  Is there a way to detect whether or not an object has called GC.SuppressFinalize? I have an object that looks something like this (full-blown Dispose pattern elided for clarity): public class ResourceWrapper { private readonly bool _ownsResource; private readonly UnmanagedResource _resource; public ResourceWrapper(UnmanagedResource resource, bool ownsResource) { _resource = resource; _ownsResource = ownsResource; if (!ownsResource) GC.SuppressFinalize(this); } ~ResourceWrapper() { if (_ownsResource) // clean up the unmanaged resource } } If the ownsResource constructor parameter is false, then the finalizer will have nothing to do -- so it seems reasonable (if a bit quirky) to call GC.SuppressFinalize right from the constructor. However, because this behavior is quirky, I'm very tempted to note it in an XML doc comment... and if I'm tempted to comment it, then I ought to write a unit test for it. But while System.GC has methods to set an object's finalizability (SuppressFinalize, ReRegisterForFinalize), I don't see any methods to get an object's finalizability. Is there any way to query whether GC.SuppressFinalize has been called on a given instance, short of buying Typemock or writing my own CLR host?

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• Release Excel Object In My Destructor

  - by Murat

  Hi all, I'm writing a Excel class using Microsoft.Interropt.Excel DLL. I finish all function but I have an error in my Destructor. I Want to save all changes to my file and I want to release all source. I want to all of them in my destructor. But In my destructor, Excel.ApplicationClass, Workbook and Worksheet objects are fill by an Exception which have message "COM object that has been separated from its underlying RCW cannot be used." So I can't save nothing, close nothing because i can't access workbook or worksheet object. Can't I access the class private members in Destructor?

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• Why do finalizers have a "severe performance penalty"?

  - by kunjaan

  Effective Java says : There is a severe performance penalty for using finalizers. Why is it slower to destroy an object using the finalizers?

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• MySQL Throws NullReferenceException in Finalize... How are you coping with this?

  - by Cyril Gupta

  I am using MySQL with the .Net connector on 64 bit Windows. For some reason Mysql is throwing a NullReferenceException in Finalize. This is the problem here and it seems that its due to a bug described here. This bug was reported in 6.22, but I am getting the issue with 6.23 too so apparently it is not fixed. I am using MySQL both with the helper classes, and by instantiating the connection and the Mysqlcommand object. Does anybody have any idea what part of my code do I need to change to fix this issue? Cause even though this is a bug in Mysql this is not universal because I am not getting the problem in my other projects. MySQL bug report has no details on how to reproduce it either. Any suggestions?

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• What happens if an exception is thrown during finalize()

  - by Psykocyber

  What would happen if an exception is thrown during the execution of finalize()? Is the stack unwind like normally? Does it continue finalize() and ignore the exception? Does it stop finalize() and continue GC the object? Or something else? I'm not looking for guidelines of using finalize() there are plently of pages explaining that.

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• What happens if an exception is thrown in finalize()

  - by Psykocyber

  What would happen if an exception is thrown during the execution of finalize()? Is the stack unwind like normally? Does it continue finalize() and ignore the exception? Does it stop finalize() and continue GC the object? Or something else? I'm not looking for guidelines of using finalize() there are plently of pages explaining that.

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• C# Finalize/Dispose pattern

  - by robUK

  Hello, C# 2008 I have been working on this for a while now. And I am still confused about some issues. My questions below 1) I know that you only need a finalizer if you are disposing of unmanaged resources. However, if you are using managed resources that make calls to unmanaged resources. Would you still need to implement a finalizer? 2) However, if you develop a class that doesn't use any unmanged resources directly or indirectly and you implement the IDisposable so that clients of your class can use the 'using statement'. Would it be acceptable to implement the IDisposable just so that clients of your class can use the using statement? using(myClass objClass = new myClass()) { // Do stuff here } 3) I have developed this simple code below to demostrate the Finalize/dispose pattern: public class NoGateway : IDisposable { private WebClient wc = null; public NoGateway() { wc = new WebClient(); wc.DownloadStringCompleted += wc_DownloadStringCompleted; } // Start the Async call to find if NoGateway is true or false public void NoGatewayStatus() { // Start the Async's download // Do other work here wc.DownloadStringAsync(new Uri(www.xxxx.xxx)); } private void wc_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e) { // Do work here } // Dispose of the NoGateway object public void Dispose() { wc.DownloadStringCompleted -= wc_DownloadStringCompleted; wc.Dispose(); GC.SuppressFinalize(this); } } Question about the source code: 1) Here I have not added the finalizer. And normally the finalizer will be called by the GC, and the finalizer will call the Dispose. As I don't have the finalizer, when do I call the Dispose method? Is it the client of the class that has to call it? So my class in the example is called NoGateway and the client could use and dispose of the class like this: Would the Dispose method be automatically called when execution reaches the end of the using block? using(NoGateway objNoGateway = new NoGateway()) { // Do stuff here } Or does the client have to manually call the dispose method i.e.? NoGateway objNoGateway = new NoGateway(); // Do stuff with object objNoGateway.Dispose(); // finished with it Many thanks for helping with all these questions, 2) I am using the webclient class in my 'NoGateway' class. Because the webclient implements the IDisposable interface. Does this mean that the webclient indirectly uses unmanaged resources? Is there any hard and fast rule to follow about this. How do I know that a class uses unmanaged resources?

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• Thread.Interrupt Is Evil

  - by Alois Kraus

  Recently I have found an interesting issue with Thread.Interrupt during application shutdown. Some application was crashing once a week and we had not really a clue what was the issue. Since it happened not very often it was left as is until we have got some memory dumps during the crash. A memory dump usually means WindDbg which I really like to use (I know I am one of the very few fans of it).  After a quick analysis I did find that the main thread already had exited and the thread with the crash was stuck in a Monitor.Wait. Strange Indeed. Running the application a few thousand times under the debugger would potentially not have shown me what the reason was so I decided to what I call constructive debugging. I did create a simple Console application project and try to simulate the exact circumstances when the crash did happen from the information I have via memory dump and source code reading. The thread that was  crashing was actually MS code from an old version of the Microsoft Caching Application Block. From reading the code I could conclude that the main thread did call the Dispose method on the CacheManger class which did call Thread.Interrupt on the cache scavenger thread which was just waiting for work to do. My first version of the repro looked like this   static void Main(string[] args) { Thread t = new Thread(ThreadFunc) { IsBackground = true, Name = "Test Thread" }; t.Start(); Console.WriteLine("Interrupt Thread"); t.Interrupt(); } static void ThreadFunc() { while (true) { object value = Dequeue(); // block until unblocked or awaken via ThreadInterruptedException } } static object WaitObject = new object(); static object Dequeue() { object lret = "got value"; try { lock (WaitObject) { } } catch (ThreadInterruptedException) { Console.WriteLine("Got ThreadInterruptException"); lret = null; } return lret; } I do start a background thread and call Thread.Interrupt on it and then directly let the application terminate. The thread in the meantime does plenty of Monitor.Enter/Leave calls to simulate work on it. This first version did not crash. So I need to dig deeper. From the memory dump I did know that the finalizer thread was doing just some critical finalizers which were closing file handles. Ok lets add some long running finalizers to the sample. class FinalizableObject : CriticalFinalizerObject { ~FinalizableObject() { Console.WriteLine("Hi we are waiting to finalize now and block the finalizer thread for 5s."); Thread.Sleep(5000); } } class Program { static void Main(string[] args) { FinalizableObject fin = new FinalizableObject(); Thread t = new Thread(ThreadFunc) { IsBackground = true, Name = "Test Thread" }; t.Start(); Console.WriteLine("Interrupt Thread"); t.Interrupt(); GC.KeepAlive(fin); // prevent finalizing it too early // After leaving main the other thread is woken up via Thread.Abort // while we are finalizing. This causes a stackoverflow in the CLR ThreadAbortException handling at this time. } With this changed Main method and a blocking critical finalizer I did get my crash just like the real application. The funny thing is that this is actually a CLR bug. When the main method is left the CLR does suspend all threads except the finalizer thread and declares all objects as garbage. After the normal finalizers were called the critical finalizers are executed to e.g. free OS handles (usually). Remember that I did call Thread.Interrupt as one of the last methods in the Main method. The Interrupt method is actually asynchronous and does wake a thread up and throws a ThreadInterruptedException only once unlike Thread.Abort which does rethrow the exception when an exception handling clause is left. It seems that the CLR does not expect that a frozen thread does wake up again while the critical finalizers are executed. While trying to raise a ThreadInterrupedException the CLR goes down with an stack overflow. Ups not so nice. Why has this nobody noticed for years is my next question. As it turned out this error does only happen on the CLR for .NET 4.0 (x86 and x64). It does not show up in earlier or later versions of the CLR. I have reported this issue on connect here but so far it was not confirmed as a CLR bug. But I would be surprised if my console application was to blame for a stack overflow in my test thread in a Monitor.Wait call. What is the moral of this story? Thread.Abort is evil but Thread.Interrupt is too. It is so evil that even the CLR of .NET 4.0 contains a race condition during the CLR shutdown. When the CLR gurus can get it wrong the chances are high that you get it wrong too when you use this constructs. If you do not believe me see what Patrick Smacchia does blog about Thread.Abort and List.Sort. Not only the CLR creators can get it wrong. The BCL writers do sometimes have a hard time with correct exception handling as well. If you do tell me that you use Thread.Abort frequently and never had problems with it I do suspect that you do not have looked deep enough into your application to find such sporadic errors.

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• StackOverFlowError while creating Mac object on AS400/Java

  - by Prasanna K Rao

  Hello all, I am a newbie to AS400-Java programming. I am trying to create my first program to test the implementation of Message Authentication Code (MAC). I am trying to use the HMACSHA1 hash function. My (Java 1.4) program runs fine on a dev box (V5R4).But fails terribly on the QA box (V5R3). My program is as below: ===================================================== import java.security.InvalidKeyException; import java.security.NoSuchAlgorithmException; import java.security.Security; import java.security.Provider; import javax.crypto.Mac; import javax.crypto.spec.SecretKeySpec; import javax.crypto.SecretKey; public class Test01 { private static final String HMAC_SHA1_ALGORITHM = "HmacSHA1"; public static void main (String [] arguments) { byte[] key = { 1,2,3,4,5,6,7,8}; SecretKeySpec SHA1key = new SecretKeySpec(key, "HmacSHA1"); Mac hmac; String strFinalRslt = ""; try { hmac = Mac.getInstance("HmacSHA1"); hmac.init(SHA1key); byte[] result = hmac.doFinal(); strFinalRslt = toHexString(result); }catch (NoSuchAlgorithmException e) { // TODO Auto-generated catch block e.printStackTrace(); }catch (InvalidKeyException e) { // TODO Auto-generated catch block e.printStackTrace(); }catch(StackOverflowError e){ e.printStackTrace(); } System.out.println(strFinalRslt); System.out.println("All done!!!"); } public static byte[] fromHexString ( String s ) { int stringLength = s.length(); if ( (stringLength & 0x1) != 0 ) { throw new IllegalArgumentException ( "fromHexString requires an even number of hex characters" ); } byte[] b = new byte[stringLength / 2]; for ( int i=0,j=0; i 4] ); //look up low nibble char sb.append( hexChar [b[i] & 0x0f] ); } return sb.toString(); } static char[] hexChar = { '0' , '1' , '2' , '3' , '4' , '5' , '6' , '7' , '8' , '9' , 'a' , 'b' , 'c' , 'd' , 'e' , 'f'}; } This program compiles fine and gets the correct response on my win-xp client and also my dev box. But, fails with the following error on the QA box: java.lang.StackOverflowError at java.lang.Throwable.(Throwable.java:180) at java.lang.Error.(Error.java:37) at java.lang.StackOverflowError.(StackOverflowError.java:24) at java.io.Os400FileSystem.list(Native method) at java.io.File.list(File.java:922) at javax.crypto.b.e(Unknown source) at javax.crypto.b.a(Unknown source) at javax.crypto.b.c(Unknown source) at javax.crypto.b£0.run(Unknown source) at javax.crypto.b.(Unknown source) at javax.crypto.Mac.getInstance(Unknown source) I have verified the java.security file and entry corresponding to the jce files are all ok. The DMPJVM command gives me the following response: Thu Jun 03 12:25:34 E Java Virtual Machine Information 016822/QPGMR/11111 ........................................................................ . Classpath . ........................................................................ java.version=1.4 sun.boot.class.path=/QIBM/ProdData/OS400/Java400/jdk/lib/jdkptf14.zip:/QIBM /ProdData/OS400/Java400/ext/ibmjssefw.jar:/QIBM/ProdData/CAP/ibmjsseprovide r.jar:/QIBM/ProdData/OS400/Java400/ext/ibmjsseprovider2.jar:/QIBM/ProdData/ OS400/Java400/ext/ibmpkcs11impl.jar:/QIBM/ProdData/CAP/ibmjssefips.jar:/QIB M/ProdData/OS400/Java400/jdk/lib/IBMiSeriesJSSE.jar:/QIBM/ProdData/OS400/Ja va400/jdk/lib/jce.jar:/QIBM/ProdData/OS400/Java400/jdk/lib/jaas.jar:/QIBM/P rodData/OS400/Java400/jdk/lib/ibmcertpathfw.jar:/QIBM/ProdData/OS400/Java40 0/jdk/lib/ibmcertpathprovider.jar:/QIBM/ProdData/OS400/Java400/ext/ibmpkcs. jar:/QIBM/ProdData/OS400/Java400/jdk/lib/ibmjgssfw.jar:/QIBM/ProdData/OS400 /Java400/jdk/lib/ibmjgssprovider.jar:/QIBM/ProdData/OS400/Java400/jdk/lib/s ecurity.jar:/QIBM/ProdData/OS400/Java400/jdk/lib/charsets.jar:/QIBM/ProdDat a/OS400/Java400/jdk/lib/resources.jar:/QIBM/ProdData/OS400/Java400/jdk/lib/ rt.jar:/QIBM/ProdData/OS400/Java400/jdk/lib/sunrsasign.jar:/QIBM/ProdData/O S400/Java400/ext/IBMmisc.jar:/QIBM/ProdData/Java400/ java.class.path=/myhome/lib/commons-codec-1.3.jar:/myhome/lib/commons-httpc lient-3.1.jar:/myhome/lib/commons-logging-1.1.jar:/myhome/lib/log4j-1.2.15.jar:/myhome/lib/log4j-core.jar ; java.ext.dirs=/QIBM/ProdData/OS400/Java400/jdk/lib/ext:/QIBM/UserData/Java4 00/ext:/QIBM/ProdData/Java400/jdk14/lib/ext java.library.path=/QSYS.LIB/ROBOTLIB.LIB:/QSYS.LIB/QTEMP.LIB:/QSYS.LIB/ODIP GM.LIB:/QSYS.LIB/QGPL.LIB ........................................................................ . Garbage Collection . ........................................................................ Garbage collector parameters Initial size: 16384 K Max size: 240000000 K Current values Heap size: 437952 K Garbage collections: 58 Additional values JIT heap size: 53824 K JVM heap size: 55752 K Last GC cycle time: 1333 ms ........................................................................ . Thread information . ........................................................................ Information for 4 thread(s) of 4 thread(s) processed Thread: 00000004 Thread-0 TDE: B00380000BAA0000 Thread priority: 5 Thread status: Running Thread group: main Runnable: java/lang/Thread Stack: java/io/Os400FileSystem.list(Ljava/io/File;)[Ljava/lang/String;+0 (Os400FileSystem.java:0) java/io/File.list()[Ljava/lang/String;+19 (File.java:922) javax/crypto/b.e()[B+127 (:0) javax/crypto/b.a(Ljava/security/cert/X509Certificate;)V+7 (:0) javax/crypto/b.access$500(Ljava/security/cert/X509Certificate;)V+1 (:0) javax/crypto/b$0.run()Ljava/lang/Object;+98 (:0) javax/crypto/b.()V+507 (:0) javax/crypto/Mac.getInstance(Ljava/lang/String;)Ljavax/crypto/Mac;+10 (:0) Locks: None Thread: 00000007 jitcompilethread TDE: B00380000BD58000 Thread priority: 5 Thread status: Java wait Thread group: system Runnable: java/lang/Thread Stack: None Locks: None Thread: 00000005 Reference Handler TDE: B00380000BAAC000 Thread priority: 10 Thread status: Waiting Wait object: java/lang/ref/Reference$Lock Thread group: system Runnable: java/lang/ref/Reference$ReferenceHandler Stack: java/lang/Object.wait()V+1 (Object.java:452) java/lang/ref/Reference$ReferenceHandler.run()V+47 (Reference.java:169) Locks: None Thread: 00000006 Finalizer TDE: B00380000BAB3000 Thread priority: 8 Thread status: Waiting Wait object: java/lang/ref/ReferenceQueue$Lock Thread group: system Runnable: java/lang/ref/Finalizer$FinalizerThread Stack: java/lang/ref/ReferenceQueue.remove(J)Ljava/lang/ref/Reference;+43 (ReferenceQueue.java:111) java/lang/ref/ReferenceQueue.remove()Ljava/lang/ref/Reference;+1 (ReferenceQueue.java:127) java/lang/ref/Finalizer$FinalizerThread.run()V+3 (Finalizer.java:171) Locks: None ........................................................................ . Class loader information . ........................................................................ 0 Default class loader 1 sun/reflect/DelegatingClassLoader 2 sun/misc/Launcher$ExtClassLoader ........................................................................ . GC heap information . ........................................................................ Loader Objects Class name ------ ------- ---------- 0 1493 [C 0 2122181 java/lang/String 0 47 [Ljava/util/Hashtable$Entry; 0 68 [Ljava/lang/Object; 0 1016 java/lang/Class 0 31 java/util/HashMap 0 37 java/util/Hashtable 0 2 java/lang/ThreadGroup 0 2 java/lang/RuntimePermission 0 2 java/lang/ref/ReferenceQueue$Null 0 5 java/lang/ref/ReferenceQueue 0 50 java/util/Vector 0 4 java/util/Stack 0 3 sun/misc/SoftCache 0 1 [Ljava/lang/ThreadGroup; 0 5 [Ljava/io/ObjectStreamField; 0 1 sun/reflect/ReflectionFactory 0 7 java/lang/ref/ReferenceQueue$Lock 0 10 java/lang/Object 0 1 java/lang/String$CaseInsensitiveComparator 0 1 java/util/Hashtable$EmptyEnumerator 0 1 java/util/Hashtable$EmptyIterator 0 33 [Ljava/util/HashMap$Entry; 0 19210 [J 0 1 sun/nio/cs/StandardCharsets 0 5 java/util/TreeMap 0 1075 java/util/TreeMap$Entry 0 469 [Ljava/lang/String; 0 1 java/lang/StringBuffer 0 2 java/io/FileInputStream 0 2 java/io/FileOutputStream 0 2 java/io/BufferedOutputStream 0 1 java/lang/reflect/ReflectPermission 0 1 [[Ljava/lang/ref/SoftReference; 0 2 [Ljava/lang/ref/SoftReference; 0 2 sun/nio/cs/Surrogate$Parser 0 3 sun/misc/Signal 0 1 [Ljava/io/File; 0 6 java/io/File 0 1 java/util/BitSet 0 17 sun/reflect/NativeConstructorAccessorImpl 0 2 java/net/URLClassLoader$ClassFinder 0 12 java/util/ArrayList 0 32 java/io/RandomAccessFile 0 16 java/lang/Thread 0 1 java/lang/ref/Reference$ReferenceHandler 0 1 java/lang/ref/Finalizer$FinalizerThread 0 266 [B 0 2 java/util/Properties 0 71 java/lang/ref/Finalizer 0 2 com/ibm/nio/cs/DirectEncoder 0 38 java/lang/reflect/Constructor 0 33 java/util/jar/JarFile 0 19200 java/lang/StackOverflowError 0 5 java/security/AccessControlContext 0 2 [Ljava/lang/Thread; 0 4 java/lang/OutOfMemoryError 0 1065 java/util/Hashtable$Entry 0 1 java/io/BufferedInputStream 0 2 java/io/PrintStream 0 2 java/io/OutputStreamWriter 0 428 [I 0 3 java/lang/ClassLoader$NativeLibrary 0 25 java/util/Locale 0 3 sun/misc/URLClassPath 0 30 java/util/zip/Inflater 0 612 java/util/HashMap$Entry 0 2 java/io/FilePermission 0 10 java/io/ObjectStreamField 0 1 java/security/BasicPermissionCollection 0 2 java/security/ProtectionDomain 0 1 java/lang/Integer$1 0 1 java/lang/ref/Reference$Lock 0 1 java/lang/Shutdown$Lock 0 1 java/lang/Runtime 0 36 java/io/FileDescriptor 0 1 java/lang/Long$1 0 202 java/lang/Long 0 3 java/lang/ThreadLocal 0 3 java/nio/charset/CodingErrorAction 0 2 java/nio/charset/CoderResult 0 1 java/nio/charset/CoderResult$1 0 1 java/nio/charset/CoderResult$2 0 1 sun/misc/Unsafe 0 2 java/nio/ByteOrder 0 1 java/io/Os400FileSystem 0 3 java/lang/Boolean 0 1 java/lang/Terminator$1 0 23 java/lang/Integer 0 2 sun/misc/NativeSignalHandler 0 1 sun/misc/Launcher$Factory 0 1 sun/misc/Launcher 0 53 [Ljava/lang/Class; 0 1 java/lang/reflect/ReflectAccess 0 18 sun/reflect/DelegatingConstructorAccessorImpl 0 1 sun/net/www/protocol/file/Handler 0 3 java/util/HashSet 0 3 sun/net/www/protocol/jar/Handler 0 1 java/util/jar/JavaUtilJarAccessImpl 0 1 java/net/UnknownContentHandler 0 2 [Ljava/security/Principal; 0 10 [Ljava/security/cert/Certificate; 0 2 sun/misc/AtomicLongCSImpl 0 3 sun/reflect/DelegatingMethodAccessorImpl 0 1 sun/security/util/ByteArrayLexOrder 0 1 sun/security/util/ByteArrayTagOrder 0 7 sun/security/x509/CertificateVersion 0 7 sun/security/x509/CertificateSerialNumber 0 7 sun/security/x509/SerialNumber 0 7 sun/security/x509/CertificateAlgorithmId 0 7 sun/security/x509/CertificateIssuerName 0 60 sun/security/x509/RDN 0 60 [Lsun/security/x509/AVA; 0 67 sun/security/util/DerInputStream 0 3 [Ljava/math/BigInteger; 0 2 com/ibm/nio/cs/Converter 0 2 sun/nio/cs/StreamEncoder$CharsetSE 0 35 java/lang/ref/SoftReference 0 2 java/nio/HeapByteBuffer 0 2 java/io/BufferedWriter 0 33 sun/misc/URLClassPath$JarLoader 0 4 java/lang/ThreadLocal$ThreadLocalMap$Entry 0 76 java/net/URL 0 1 sun/misc/Launcher$ExtClassLoader 0 1 sun/misc/Launcher$AppClassLoader 0 4 java/lang/Throwable 0 7 java/lang/reflect/Method 0 2 sun/misc/URLClassPath$FileLoader 0 2 java/security/CodeSource 0 2 java/security/Permissions 0 2 java/io/FilePermissionCollection 0 1 java/lang/ThreadLocal$ThreadLocalMap 0 1 javax/crypto/spec/SecretKeySpec 0 17 java/util/jar/Attributes$Name 0 1 [Ljava/lang/ThreadLocal$ThreadLocalMap$Entry; 0 1 java/security/SecureRandom 0 2 sun/security/provider/Sun 0 1 java/util/jar/JarFile$JarFileEntry 0 1 java/util/jar/JarVerifier 0 3 sun/reflect/NativeMethodAccessorImpl 0 116 sun/security/util/ObjectIdentifier 0 1 java/lang/Package 0 2 [S 0 104 java/math/BigInteger 0 20 sun/security/x509/AlgorithmId 0 14 sun/security/x509/X500Name 0 14 [Lsun/security/x509/RDN; 0 60 sun/security/x509/AVA 0 67 sun/security/util/DerValue 0 67 sun/security/util/DerInputBuffer 0 21 sun/security/x509/AVAKeyword 0 6 sun/security/x509/X509CertImpl 0 7 sun/security/x509/X509CertInfo 0 1 [Lsun/security/util/ObjectIdentifier; 0 1 [[Ljava/lang/Byte; 0 3 [[B 0 7 sun/security/provider/DSAPublicKey 0 7 sun/security/x509/AuthorityKeyIdentifierExtension 0 12 [Ljava/lang/Byte; 0 14 java/lang/Byte 0 7 sun/security/x509/CertificateSubjectName 0 7 sun/security/x509/CertificateX509Key 0 14 sun/security/x509/KeyIdentifier 0 4 [Z 0 5 sun/text/Normalizer$Mode 0 7 sun/security/x509/CertificateValidity 0 14 java/util/Date 0 7 sun/security/provider/DSAParameters 0 7 sun/security/util/BitArray 0 7 sun/security/x509/CertificateExtensions 0 7 java/security/AlgorithmParameters 0 7 sun/security/x509/SubjectKeyIdentifierExtension 0 5 sun/security/x509/BasicConstraintsExtension 0 2 sun/security/x509/KeyUsageExtension 0 1 sun/text/CompactCharArray 0 1 sun/text/CompactByteArray 0 1 sun/net/www/protocol/jar/JarFileFactory 0 1 java/util/Collections$EmptySet 0 1 java/util/Collections$EmptyList 0 1 java/util/Collections$ReverseComparator 0 1 com/ibm/security/jgss/i18n/PropertyResource 0 1 javax/crypto/b$0 0 1 sun/security/provider/X509Factory 0 1 sun/reflect/BootstrapConstructorAccessorImpl 1 1 sun/reflect/GeneratedConstructorAccessor3202134454 2 1 com/ibm/crypto/provider/IBMJCE 0 6 java/util/ResourceBundle$LoaderReference 0 1 [Lsun/security/x509/NetscapeCertTypeExtension$MapEntry; 0 1 com/sun/rsajca/Provider 0 1 com/ibm/security/cert/IBMCertPath 0 1 com/ibm/as400/ibmonly/net/ssl/Provider 0 1 com/ibm/jsse/IBMJSSEProvider 0 1 com/ibm/security/jgss/IBMJGSSProvider 0 5 org/ietf/jgss/Oid 0 1 java/util/PropertyResourceBundle 0 7 java/util/ResourceBundle$ResourceCacheKey 0 2 sun/net/www/protocol/jar/URLJarFile 0 6 sun/misc/SoftCache$ValueCell 0 1 java/util/Random 0 1 java/util/Collections$EmptyMap 0 112 com/ibm/security/util/ObjectIdentifier 0 5 java/security/Security$ProviderProperty 0 1 java/security/cert/CertificateFactory 0 1 sun/security/provider/SecureRandom 0 2 java/security/MessageDigest$Delegate 0 2 sun/security/provider/SHA 0 1 sun/util/calendar/ZoneInfo 0 4 com/ibm/security/x509/X500Name 0 2 [Ljava/security/cert/X509Certificate; 0 1 sun/reflect/DelegatingClassLoader 0 1 sun/security/x509/NetscapeCertTypeExtension 0 7 sun/security/x509/NetscapeCertTypeExtension$MapEntry 0 3 [[Ljava/lang/String; 0 3 java/util/Arrays$ArrayList 0 7 com/ibm/security/x509/NetscapeCertTypeExtension$MapEntry 0 1 com/ibm/security/validator/EndEntityChecker 0 1 java/util/AbstractList$Itr 0 1 com/ibm/security/util/ByteArrayLexOrder 0 1 com/ibm/security/util/ByteArrayTagOrder 0 18 [Lcom/ibm/security/x509/AVA; 0 18 com/ibm/security/util/DerInputStream 0 5 com/ibm/security/util/text/Normalizer$Mode 0 1 com/ibm/security/validator/SimpleValidator 0 1 [Lcom/ibm/security/x509/NetscapeCertTypeExtension$MapEntry; 0 4 [Lcom/ibm/security/x509/RDN; 0 1 java/util/Hashtable$Enumerator 0 4 java/util/LinkedHashMap$Entry 0 1 sun/text/resources/LocaleElements 0 1 sun/text/resources/LocaleElements_en 0 22 com/ibm/security/x509/AVAKeyword 0 4 javax/security/auth/x500/X500Principal 0 18 com/ibm/security/x509/RDN 0 18 com/ibm/security/x509/AVA 0 18 com/ibm/security/util/DerInputBuffer 0 18 com/ibm/security/util/DerValue 0 1 com/ibm/security/util/text/CompactCharArray 0 1 com/ibm/security/util/text/CompactByteArray 0 2 java/util/LinkedHashMap 0 1 java/net/InetAddress$1 0 2 [Ljava/net/InetAddress; 0 2 java/net/InetAddress$Cache 0 1 java/net/Inet4AddressImpl 0 3 java/net/Inet4Address 0 2 java/net/InetAddress$CacheEntry ........................................................................ . Global registry information . ........................................................................ Loader Objects Class name ------ ------- ---------- 0 23 [C 0 1017 java/lang/Class 0 1 java/lang/ref/Reference$ReferenceHandler 0 1 java/lang/ref/Finalizer$FinalizerThread 0 1 sun/misc/Launcher$AppClassLoader 0 32 java/io/RandomAccessFile 0 32 [B Can someone please advise me? Thanks a lot, Prasanna

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• Should I use IDisposable for purely managed resources?

  - by John Gietzen

  Here is the scenario: I have an object called a Transaction that needs to make sure that only one entity has permission to edit it at any given time. In order to facilitate a long-lived lock, I have the class generating a token object that can be used to make the edits. You would use it like this: var transaction = new Transaction(); using (var tlock = transaction.Lock()) { transaction.Update(data, tlock); } Now, I want the TransactionLock class to implement IDisposable so that its usage can be clear. But, I don't have any unmanaged resources to dispose. however, the TransctionLock object itself is a sort of "unmanaged resource" in the sense that the CLR doesn't know how to properly finalize it. All of this would be fine and dandy, I would just use IDisposable and be done with it. However, my issue comes when I try to do this in the finalizer: ~TransactionLock() { this.Dispose(false); } I want the finalizer to release the transaction from the lock, if possible. How, in the finalizer, do I detect if the parent transaction (this.transaction) has already been finalized? Is there a better pattern I should be using? The Transaction class looks something like this: public sealed class Transaction { private readonly object lockMutex = new object(); private TransactionLock currentLock; public TransactionLock Lock() { lock (this.lockMutex) { if (this.currentLock != null) throw new InvalidOperationException(/* ... */); this.currentLock = new TransactionLock(this); return this.currentLock; } } public void Update(object data, TransactionLock tlock) { lock (this.lockMutex) { this.ValidateLock(tlock); // ... } } internal void ValidateLock(TransactionLock tlock) { if (this.currentLock == null) throw new InvalidOperationException(/* ... */); if (this.currentLock != tlock) throw new InvalidOperationException(/* ... */); } internal void Unlock(TransactionLock tlock) { lock (this.lockMutex) { this.ValidateLock(tlock); this.currentLock = null; } } }

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• Java thread dump where main thread has no call stack? (jsvc)

  - by dwhsix

  We have a java process running as a daemon (under jsvc). Every several days it just stops doing any work; output to the logfile stops (it is pretty verbose, on 5-minute intervals) and it consumes no CPU or IO. There are no exceptions logged in the logfile nor in syserr or sysout. The last log statement is just prior to a db commit being done, but there is no open connection on the db server (MySQL) and reviewing the code, there should always be additional log output after that, even if it had encountered an exception that was going to bubble up. The most curious thing I find is that in the thread dump (included below), there's no thread in our code at all, and the main thread seems to have no context whatsoever: "main" prio=10 tid=0x0000000000614000 nid=0x445d runnable [0x0000000000000000] java.lang.Thread.State: RUNNABLE As noted earlier, this is a daemon process running using jsvc, but I don't know if that has anything to do with it (I can restructure the code to also allow running it directly, to test). Any suggestions on what might be happening here? Thanks... dwh Full thread dump: Full thread dump Java HotSpot(TM) 64-Bit Server VM (14.2-b01 mixed mode): "MySQL Statement Cancellation Timer" daemon prio=10 tid=0x00002aaaf81b8800 nid=0x447b in Object.wait() [0x00002aaaf6a22000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x00002aaab5556d50> (a java.util.TaskQueue) at java.lang.Object.wait(Object.java:485) at java.util.TimerThread.mainLoop(Timer.java:483) - locked <0x00002aaab5556d50> (a java.util.TaskQueue) at java.util.TimerThread.run(Timer.java:462) "Low Memory Detector" daemon prio=10 tid=0x00000000006a4000 nid=0x4479 runnable [0x0000000000000000] java.lang.Thread.State: RUNNABLE "CompilerThread1" daemon prio=10 tid=0x00000000006a1000 nid=0x4477 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "CompilerThread0" daemon prio=10 tid=0x000000000069d000 nid=0x4476 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "Signal Dispatcher" daemon prio=10 tid=0x000000000069b000 nid=0x4465 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "Finalizer" daemon prio=10 tid=0x0000000000678800 nid=0x4464 in Object.wait() [0x00002aaaf61d6000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x00002aaab54a1cb8> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:118) - locked <0x00002aaab54a1cb8> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:134) at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:159) "Reference Handler" daemon prio=10 tid=0x0000000000676800 nid=0x4463 in Object.wait() [0x00002aaaf60d5000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x00002aaab54a1cf0> (a java.lang.ref.Reference$Lock) at java.lang.Object.wait(Object.java:485) at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:116) - locked <0x00002aaab54a1cf0> (a java.lang.ref.Reference$Lock) "main" prio=10 tid=0x0000000000614000 nid=0x445d runnable [0x0000000000000000] java.lang.Thread.State: RUNNABLE "VM Thread" prio=10 tid=0x0000000000670000 nid=0x4462 runnable "GC task thread#0 (ParallelGC)" prio=10 tid=0x000000000061e000 nid=0x445e runnable "GC task thread#1 (ParallelGC)" prio=10 tid=0x0000000000620000 nid=0x445f runnable "GC task thread#2 (ParallelGC)" prio=10 tid=0x0000000000622000 nid=0x4460 runnable "GC task thread#3 (ParallelGC)" prio=10 tid=0x0000000000623800 nid=0x4461 runnable "VM Periodic Task Thread" prio=10 tid=0x00000000006a6800 nid=0x447a waiting on condition JNI global references: 797 Heap PSYoungGen total 162944K, used 48388K [0x00002aaadff40000, 0x00002aaaf2ab0000, 0x00002aaaf5490000) eden space 102784K, 47% used [0x00002aaadff40000,0x00002aaae2e81170,0x00002aaae63a0000) from space 60160K, 0% used [0x00002aaaeb850000,0x00002aaaeb850000,0x00002aaaef310000) to space 86720K, 0% used [0x00002aaae63a0000,0x00002aaae63a0000,0x00002aaaeb850000) PSOldGen total 699072K, used 699072K [0x00002aaab5490000, 0x00002aaadff40000, 0x00002aaadff40000) object space 699072K, 100% used [0x00002aaab5490000,0x00002aaadff40000,0x00002aaadff40000) PSPermGen total 21248K, used 9252K [0x00002aaab0090000, 0x00002aaab1550000, 0x00002aaab5490000) object space 21248K, 43% used [0x00002aaab0090000,0x00002aaab09993e8,0x00002aaab1550000)

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• restrict documents for mapreduce with mongoid

  - by theBernd

  I implemented the pearson product correlation via map / reduce / finalize. The missing part is to restrict the documents (representing users) to be processed via a filter query. For a simple query like mapreduce(mapper, reducer, :finalize => finalizer, :query => { :name => 'Bernd' }) I get this to work. But my filter criteria is a little bit more complicated: I have one set of preferences which need to have at least one common element and another set of preferences which may not have a common element. In a later step I also want to restrict this to documents (users) within a certain geographical distance. Currently I have this code working in my map function, but I would prefer to separate this into either query params as supported by mongoid or a javascript function. All my attempts to solve this failed since the code is either ignored or raises an error. I did a couple of tests. A regular find like User.where(:name.in => ['Arno', 'Bernd', 'Claudia']) works and returns #<Mongoid::Criteria:0x00000101f0ea40 @selector={:name=>{"$in"=>["Arno", "Bernd", "Claudia"]}}, @options={}, @klass=User, @documents=[]> Trying the same with mapreduce User.collection. mapreduce(mapper, reducer, :finalize => finalizer, :query => { :name.in => ['Arno', 'Bernd', 'Claudia'] }) fails with `serialize': keys must be strings or symbols (TypeError) in bson-1.1.5 The intermediate query parameter looks like this :query=>{#<Mongoid::Criterion::Complex:0x00000101a209e8 @key=:name, @operator="in">=>["Arno", "Bernd", "Claudia"]} and at least @operator looks a bit weird to me. I'm also uncertain if the class name can be omitted. BTW - I'm using mongodb 1.6.5-x86_64, and the mongoid 2.0.0.beta.20, mongo 1.1.5 and bson 1.1.5 gems on MacOS. What am I doing wrong? Thanks in advance.

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• Criteria for triggering garbage collection in .Net

  - by Kennet Belenky

  I've come across some curious behavior with regard to garbage collection in .Net. The following program will throw an OutOfMemoryException very quickly (after less than a second on a 32-bit, 2GB machine). The Foo finalizer is never called. class Foo { static Dictionary<Guid, WeakReference> allFoos = new Dictionary<Guid, WeakReference>(); Guid guid = Guid.NewGuid(); byte[] buffer = new byte[1000000]; static Random rand = new Random(); public Foo() { // Uncomment the following line and the program will run forever. // rand.NextBytes(buffer); allFoos[guid] = new WeakReference(this); } ~Foo() { allFoos.Remove(guid); } static public void Main(string args[]) { for (; ; ) { new Foo(); } } } If the rand.nextBytes line is uncommented, it will run ad infinitum, and the Foo finalizer is regularly invoked. Why is that? My best guess is that in the former case, either the CLR or the Windows VMM is lazy about allocating physical memory. The buffer never gets written to, so the physical memory is never used. When the address space runs out, the system crashes. In the latter case, the system runs out of physical memory before it runs out of address space, the GC is triggered and the objects are collected. However, here's the part I don't get. Assuming my theory is correct, why doesn't the GC trigger when the address space runs low? If my theory is incorrect, then what's the real explanation?

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• Tomcat 7 taking ages to start up after upgrade

  - by Lawrence

  I recently updated my server installation from Tomcat 6 to Tomcat 7, in order to take advantage of better connection pooling. My project uses Hibernate, for object persistance, a Mysql 5.5.20 database, and memcached for caching. When I was using Tomcat 6, Tomcat would start in about 8 seconds. After moving to Tomcat 7, it now takes between 75 - 80 seconds to start (this is on a Macbook pro 15", core i7 2Ghz, 8Gb of RAM). The only thing that has really changed between during the move from Tomcat 6 to 7 has been my context.xml file, which controls the connection pooling information: <Context antiJARLocking="true" reloadable="true" path=""> <Resource name="jdbc/test-db" auth="Container" type="javax.sql.DataSource" factory="org.apache.tomcat.jdbc.pool.DataSourceFactory" testOnBorrow="true" testOnReturn="false" testWhileIdle="true" validationQuery="SELECT 1" validationQueryTimeout="20000" validationInterval="30000" timeBetweenEvictionRunsMillis="60000" logValidationErrors="true" autoReconnect="true" username="webuser" password="xxxxxxx" driverClassName="com.mysql.jdbc.Driver" url="jdbc:mysql://databasename.us-east-1.rds.amazonaws.com:3306/test-db" maxActive="15" minIdle="2" maxIdle="10" maxWait="10000" maxAge="7200000"/> </Context> Now, as you can see, the database is running on Amazon RDS (where our live servers are), and thus is about 200ms round trip time away from my machine. I have already checked that I have security permissions to that database from my machine, (and anyway, it connects after 75 secs, so it cant be that). My initial thought was that Tomcat 7 and hibernate are doing something weird (like pre-instantiating a bunch of connections or something), and the latency to the database is amplifying the effects. While trying to diagnose the problem, I used jstack to get a stack trace of the Tomcat 7 server while its doing its startup thing. Here is the stack trace... Full thread dump Java HotSpot(TM) 64-Bit Server VM (20.12-b01-434 mixed mode): "Attach Listener" daemon prio=9 tid=7fa4c0038800 nid=0x10c39a000 waiting on condition [00000000] java.lang.Thread.State: RUNNABLE "Abandoned connection cleanup thread" daemon prio=5 tid=7fa4bb810000 nid=0x10f3ba000 in Object.wait() [10f3b9000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <7f40a0070> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:118) - locked <7f40a0070> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:134) at com.mysql.jdbc.NonRegisteringDriver$1.run(NonRegisteringDriver.java:93) "PoolCleaner[545768040:1352724902327]" daemon prio=5 tid=7fa4be852800 nid=0x10e772000 in Object.wait() [10e771000] java.lang.Thread.State: TIMED_WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <7f40c7c90> (a java.util.TaskQueue) at java.util.TimerThread.mainLoop(Timer.java:509) - locked <7f40c7c90> (a java.util.TaskQueue) at java.util.TimerThread.run(Timer.java:462) "localhost-startStop-1" daemon prio=5 tid=7fa4bd034800 nid=0x10d66b000 runnable [10d668000] java.lang.Thread.State: RUNNABLE at java.net.SocketInputStream.socketRead0(Native Method) at java.net.SocketInputStream.read(SocketInputStream.java:129) at com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:114) at com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:161) at com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:189) - locked <7f3673be0> (a com.mysql.jdbc.util.ReadAheadInputStream) at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:3014) at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3467) at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3456) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3997) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2468) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2629) at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2713) - locked <7f366a1c0> (a com.mysql.jdbc.JDBC4Connection) at com.mysql.jdbc.ConnectionImpl.configureClientCharacterSet(ConnectionImpl.java:1930) at com.mysql.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl.java:3571) at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2445) at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2215) - locked <7f366a1c0> (a com.mysql.jdbc.JDBC4Connection) at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:813) at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47) at sun.reflect.GeneratedConstructorAccessor10.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) at java.lang.reflect.Constructor.newInstance(Constructor.java:513) at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:399) at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:334) at org.apache.tomcat.jdbc.pool.PooledConnection.connectUsingDriver(PooledConnection.java:278) at org.apache.tomcat.jdbc.pool.PooledConnection.connect(PooledConnection.java:182) at org.apache.tomcat.jdbc.pool.ConnectionPool.createConnection(ConnectionPool.java:699) at org.apache.tomcat.jdbc.pool.ConnectionPool.borrowConnection(ConnectionPool.java:631) at org.apache.tomcat.jdbc.pool.ConnectionPool.init(ConnectionPool.java:485) at org.apache.tomcat.jdbc.pool.ConnectionPool.<init>(ConnectionPool.java:143) at org.apache.tomcat.jdbc.pool.DataSourceProxy.pCreatePool(DataSourceProxy.java:116) - locked <7f34f0dc8> (a org.apache.tomcat.jdbc.pool.DataSource) at org.apache.tomcat.jdbc.pool.DataSourceProxy.createPool(DataSourceProxy.java:103) at org.apache.tomcat.jdbc.pool.DataSourceFactory.createDataSource(DataSourceFactory.java:539) at org.apache.tomcat.jdbc.pool.DataSourceFactory.getObjectInstance(DataSourceFactory.java:237) at org.apache.naming.factory.ResourceFactory.getObjectInstance(ResourceFactory.java:143) at javax.naming.spi.NamingManager.getObjectInstance(NamingManager.java:304) at org.apache.naming.NamingContext.lookup(NamingContext.java:843) at org.apache.naming.NamingContext.lookup(NamingContext.java:154) at org.apache.naming.NamingContext.lookup(NamingContext.java:831) at org.apache.naming.NamingContext.lookup(NamingContext.java:168) at org.apache.catalina.core.NamingContextListener.addResource(NamingContextListener.java:1061) at org.apache.catalina.core.NamingContextListener.createNamingContext(NamingContextListener.java:671) at org.apache.catalina.core.NamingContextListener.lifecycleEvent(NamingContextListener.java:270) at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119) at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90) at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5173) - locked <7f46b07f0> (a org.apache.catalina.core.StandardContext) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) - locked <7f46b07f0> (a org.apache.catalina.core.StandardContext) at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559) at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303) at java.util.concurrent.FutureTask.run(FutureTask.java:138) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:680) "Catalina-startStop-1" daemon prio=5 tid=7fa4b7a5e800 nid=0x10d568000 waiting on condition [10d567000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <7f480e970> (a java.util.concurrent.FutureTask$Sync) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:156) at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:811) at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:969) at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1281) at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:218) at java.util.concurrent.FutureTask.get(FutureTask.java:83) at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1123) - locked <7f453c630> (a org.apache.catalina.core.StandardHost) at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:800) - locked <7f453c630> (a org.apache.catalina.core.StandardHost) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) - locked <7f453c630> (a org.apache.catalina.core.StandardHost) at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559) at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303) at java.util.concurrent.FutureTask.run(FutureTask.java:138) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:680) "GC Daemon" daemon prio=2 tid=7fa4b9912800 nid=0x10d465000 in Object.wait() [10d464000] java.lang.Thread.State: TIMED_WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <7f4506d28> (a sun.misc.GC$LatencyLock) at sun.misc.GC$Daemon.run(GC.java:100) - locked <7f4506d28> (a sun.misc.GC$LatencyLock) "Low Memory Detector" daemon prio=5 tid=7fa4b480b800 nid=0x10c8ae000 runnable [00000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread1" daemon prio=9 tid=7fa4b480b000 nid=0x10c7ab000 waiting on condition [00000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread0" daemon prio=9 tid=7fa4b480a000 nid=0x10c6a8000 waiting on condition [00000000] java.lang.Thread.State: RUNNABLE "Signal Dispatcher" daemon prio=9 tid=7fa4b4809800 nid=0x10c5a5000 runnable [00000000] java.lang.Thread.State: RUNNABLE "Surrogate Locker Thread (Concurrent GC)" daemon prio=5 tid=7fa4b4808800 nid=0x10c4a2000 waiting on condition [00000000] java.lang.Thread.State: RUNNABLE "Finalizer" daemon prio=8 tid=7fa4b793f000 nid=0x10c297000 in Object.wait() [10c296000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <7f451c8f0> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:118) - locked <7f451c8f0> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:134) at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:159) "Reference Handler" daemon prio=10 tid=7fa4b793e000 nid=0x10c194000 in Object.wait() [10c193000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <7f452e168> (a java.lang.ref.Reference$Lock) at java.lang.Object.wait(Object.java:485) at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:116) - locked <7f452e168> (a java.lang.ref.Reference$Lock) "main" prio=5 tid=7fa4b7800800 nid=0x104329000 waiting on condition [104327000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <7f480e9a0> (a java.util.concurrent.FutureTask$Sync) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:156) at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:811) at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:969) at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1281) at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:218) at java.util.concurrent.FutureTask.get(FutureTask.java:83) at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1123) - locked <7f451fd90> (a org.apache.catalina.core.StandardEngine) at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:302) - locked <7f451fd90> (a org.apache.catalina.core.StandardEngine) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) - locked <7f451fd90> (a org.apache.catalina.core.StandardEngine) at org.apache.catalina.core.StandardService.startInternal(StandardService.java:443) - locked <7f451fd90> (a org.apache.catalina.core.StandardEngine) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) - locked <7f453e810> (a org.apache.catalina.core.StandardService) at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:732) - locked <7f4506d58> (a [Lorg.apache.catalina.Service;) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) - locked <7f44f7ba0> (a org.apache.catalina.core.StandardServer) at org.apache.catalina.startup.Catalina.start(Catalina.java:684) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:322) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:451) "VM Thread" prio=9 tid=7fa4b7939800 nid=0x10c091000 runnable "Gang worker#0 (Parallel GC Threads)" prio=9 tid=7fa4b7802000 nid=0x10772b000 runnable "Gang worker#1 (Parallel GC Threads)" prio=9 tid=7fa4b7802800 nid=0x10782e000 runnable "Gang worker#2 (Parallel GC Threads)" prio=9 tid=7fa4b7803000 nid=0x107931000 runnable "Gang worker#3 (Parallel GC Threads)" prio=9 tid=7fa4b7804000 nid=0x107a34000 runnable "Gang worker#4 (Parallel GC Threads)" prio=9 tid=7fa4b7804800 nid=0x107b37000 runnable "Gang worker#5 (Parallel GC Threads)" prio=9 tid=7fa4b7805000 nid=0x107c3a000 runnable "Gang worker#6 (Parallel GC Threads)" prio=9 tid=7fa4b7805800 nid=0x107d3d000 runnable "Gang worker#7 (Parallel GC Threads)" prio=9 tid=7fa4b7806800 nid=0x107e40000 runnable "Concurrent Mark-Sweep GC Thread" prio=9 tid=7fa4b78e3800 nid=0x10bd0b000 runnable "Gang worker#0 (Parallel CMS Threads)" prio=9 tid=7fa4b78e2800 nid=0x10b305000 runnable "Gang worker#1 (Parallel CMS Threads)" prio=9 tid=7fa4b78e3000 nid=0x10b408000 runnable "VM Periodic Task Thread" prio=10 tid=7fa4b4815800 nid=0x10c9b1000 waiting on condition "Exception Catcher Thread" prio=10 tid=7fa4b7801800 nid=0x104554000 runnable JNI global references: 919 The only thing I can figure out from this is that it looks like the mysql jdbc drivers might have something to do with the long start up (the various stack traces I took during the start up process all pretty much look the same as this). Could anyone shed some light on what might be causing this? Have I done something dense in my context.xml? Is hibernate perhaps to blame?

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• Why an object declared in method is subject to garbage collection before the method returns?

  - by SiLent SoNG

  Consider an object declared in a method: public void foo() { final Object obj = new Object(); // A long run job that consumes tons of memory and // triggers garbage collection } Will obj be subject to garbage collection before foo() returns? UPDATE: Previously I thought obj is not subject to garbage collection until foo() returns. However, today I find myself wrong. I have spend several hours in fixing a bug and finally found the problem is caused by obj garbage collected! Can anyone explain why this happens? And if I want obj to be pinned how to achieve it? Here is the code that has problem. public class Program { public static void main(String[] args) throws Exception { String connectionString = "jdbc:mysql://<whatever>"; // I find wrap is gc-ed somewhere SqlConnection wrap = new SqlConnection(connectionString); Connection con = wrap.currentConnection(); Statement stmt = con.createStatement(ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY); stmt.setFetchSize(Integer.MIN_VALUE); ResultSet rs = stmt.executeQuery("select instance_id, doc_id from crawler_archive.documents"); while (rs.next()) { int instanceID = rs.getInt(1); int docID = rs.getInt(2); if (docID % 1000 == 0) { System.out.println(docID); } } rs.close(); //wrap.close(); } } After running the Java program, it will print the following message before it crashes: 161000 161000 ******************************** Finalizer CALLED!! ******************************** ******************************** Close CALLED!! ******************************** 162000 Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: And here is the code of class SqlConnection: class SqlConnection { private final String connectionString; private Connection connection; public SqlConnection(String connectionString) { this.connectionString = connectionString; } public synchronized Connection currentConnection() throws SQLException { if (this.connection == null || this.connection.isClosed()) { this.closeConnection(); this.connection = DriverManager.getConnection(connectionString); } return this.connection; } protected void finalize() throws Throwable { try { System.out.println("********************************"); System.out.println("Finalizer CALLED!!"); System.out.println("********************************"); this.close(); } finally { super.finalize(); } } public void close() { System.out.println("********************************"); System.out.println("Close CALLED!!"); System.out.println("********************************"); this.closeConnection(); } protected void closeConnection() { if (this.connection != null) { try { connection.close(); } catch (Throwable e) { } finally { this.connection = null; } } } }

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