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From Dvora <barak.ya...@gmail.com>
Subject Re: Possibility of using non-blocking calls for connection pools?
Date Sun, 22 Jan 2012 10:55:37 GMT

Hi,

I'm running into similar problems, have you find a way to solve/workaround
the issue?

Thanks.


dcheckoway wrote:
> 
> Hello,
> 
> I have an app that needs to make concurrent HTTP requests to a web service
> using persistent (keepalive) connections.  I'm using
> ThreadSafeClientConnManager.  I ran into a performance bottleneck, and I
> believe I've pinpointed the issue...
> 
> Affects Version(s): HttpCore 4.1.3, HttpClient 4.1.2
> 
> I construct my connection manager and client like this:
> 
>         connMgr = new
> ThreadSafeClientConnManager(SchemeRegistryFactory.createDefault(), -1,
> TimeUnit.MILLISECONDS);
>         connMgr.setMaxTotal(400);
>         connMgr.setDefaultMaxPerRoute(400);
> 
>         httpClient = new DefaultHttpClient(connMgr);
> 
> Note that this app only talks to a single URI on a single server -- thus
> defaultMaxPerRoute == maxTotal, which I think is correct...please let me
> know if that's bad!
> 
> Anyway, my app has a pool of 400 threads and generally performs quite
> well.  But when all 400 threads need a connection concurrently,
> performance
> suffers.  I've narrowed it down to contention caused by blocking calls in
> the connection manager.  For example...a thread dump shows...
> 
> About half my threads are "stuck" (well, not stuck, but slow & waiting)
> here:
> 
> "catalina-exec-347" daemon prio=10 tid=0x00007f3a54065000 nid=0x6b73
> waiting on condition [0x00007f3a29b9a000]
>    java.lang.Thread.State: WAITING (parking)
>     at sun.misc.Unsafe.park(Native Method)
>     - parking to wait for  <0x00000006147c8318> (a
> java.util.concurrent.locks.ReentrantLock$NonfairSync)
>     at java.util.concurrent.locks.LockSupport.park(LockSupport.java:158)
>     at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:811)
>     at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:842)
>     at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1178)
>     at
> java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:186)
>     at
> java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:262)
>     at
> org.apache.http.impl.conn.tsccm.ConnPoolByRoute.freeEntry(ConnPoolByRoute.java:438)
>     at
> org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager.releaseConnection(ThreadSafeClientConnManager.java:276)
>     - locked <0x000000062048ebc8> (a
> org.apache.http.impl.conn.tsccm.BasicPooledConnAdapter)
>     at
> org.apache.http.impl.conn.AbstractClientConnAdapter.releaseConnection(AbstractClientConnAdapter.java:308)
>     - locked <0x000000062048ebc8> (a
> org.apache.http.impl.conn.tsccm.BasicPooledConnAdapter)
>     at
> org.apache.http.conn.BasicManagedEntity.releaseManagedConnection(BasicManagedEntity.java:181)
>     at
> org.apache.http.conn.BasicManagedEntity.eofDetected(BasicManagedEntity.java:142)
>     at
> org.apache.http.conn.EofSensorInputStream.checkEOF(EofSensorInputStream.java:211)
>     at
> org.apache.http.conn.EofSensorInputStream.read(EofSensorInputStream.java:139)
>     ...
> 
> While the other half are "stuck" here:
> 
> "catalina-exec-346" daemon prio=10 tid=0x00007f3a4c05d000 nid=0x6b72
> waiting on condition [0x00007f3a29c9b000]
>    java.lang.Thread.State: WAITING (parking)
>     at sun.misc.Unsafe.park(Native Method)
>     - parking to wait for  <0x00000006147c8318> (a
> java.util.concurrent.locks.ReentrantLock$NonfairSync)
>     at java.util.concurrent.locks.LockSupport.park(LockSupport.java:158)
>     at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:811)
>     at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:842)
>     at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1178)
>     at
> java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:186)
>     at
> java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:262)
>     at
> org.apache.http.impl.conn.tsccm.ConnPoolByRoute.getEntryBlocking(ConnPoolByRoute.java:337)
>     at
> org.apache.http.impl.conn.tsccm.ConnPoolByRoute$1.getPoolEntry(ConnPoolByRoute.java:300)
>     at
> org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager$1.getConnection(ThreadSafeClientConnManager.java:224)
>     at
> org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:401)
>     at
> org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:820)
>     at
> org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:941)
>     ...
> 
> It's not a deadlock per se.  It's just a bottleneck, and it is causing
> very
> high latency in my app.  Below a certain threshold, i.e. when not all 400
> threads need a connection concurrently, things are fine.  But when all 400
> need a connection at once, that's when it gets painful.
> 
> I'm wondering if it might be feasible to switch to using non-blocking
> calls
> for this, i.e. with ConcurrentHashMap and/or ConcurrentLinkedQueue, or
> something of that nature?  I haven't dived into the source code yet, so
> don't slap me too hard if that suggestion was way out of line.  :-)
> 
> Do you have any suggestions, in terms of ways I might be able to work
> around this bottleneck otherwise?
> 
> Thanks!
> 
> Dan Checkoway
> 
> 

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