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From Dan Checkoway <dchecko...@gmail.com>
Subject Re: Possibility of using non-blocking calls for connection pools?
Date Sun, 22 Jan 2012 11:18:09 GMT
I looked into rolling my own connection manager, but (a) I bumped into a
whole bunch of deprecated classes, and then (b) when trying to work it in
with the latest code on trunk, I bumped into a stack full of classes that
rely on synchronization and locking.

I shelved the project for now, but at some point I'm going to need to
tackle this, since it's definitely a bottleneck...

On Sun, Jan 22, 2012 at 5:55 AM, Dvora <barak.yaish@gmail.com> wrote:

>
> 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
> >
> >
>
> --
> View this message in context:
> http://old.nabble.com/Possibility-of-using-non-blocking-calls-for-connection-pools--tp33093916p33182743.html
> Sent from the HttpClient-User mailing list archive at Nabble.com.
>
>
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