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https://issues.apache.org/jira/browse/QPID-8489?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17245809#comment-17245809
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Daniil Kirilyuk commented on QPID-8489:
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Hi [~orudyy],
Although the erroneous behavior were observed on simulation environment, we
managed to reproduce it only by interrupting or killing client processes (using
Ctrl + C in console or kill -9 PID). I'm not sure about socket handling on OS
level, but such "orphaned" connections in broker could keep looping up to 10
hours on our DEV environment (till broker was restarted). It seems that error
can also be induced by incorrect behavior of qpid-proton clients, operating on
low level and ignoring errors. Unfortunately we don't have access to the
sources of the clients producing such behavior and need to do some
reverse-engineering based on logs / monitoring data.
> Connection thread looping
> -------------------------
>
> Key: QPID-8489
> URL: https://issues.apache.org/jira/browse/QPID-8489
> Project: Qpid
> Issue Type: Bug
> Components: Broker-J
> Affects Versions: qpid-java-broker-8.0.2
> Reporter: Daniil Kirilyuk
> Priority: Minor
> Attachments: QPID-8489.log, simple_recv.cpp, thread-dump.st
>
>
> Error happens quite rarely and is not easy to reproduce. Although the problem
> was partly fixed by fixing QPID-8477, it still can be reproduced. The main
> symptom is significant increase of CPU usage even when no messages are sent
> to broker anymore. CPU usage can rise from 30% to 90% and higher, making
> broker unusable. After such CPU rise the only way to fix broker will be
> restarting it.
> Analysis has shown, that error occurs with CPP proton client in cases when
> 1) SSL connection is used
> 2) connection errors on client side are ignored
> 3) connection is dropped due to the client process termination / network
> disconnection
> *Steps to reproduce*
> # Java broker should be installed
> # Broker should be configured to allow one connection
> # Prepare certificates
> # Install Qpid::Proton 0.28.0
> wget
> [http://archive.apache.org/dist/qpid/proton/0.28.0/qpid-proton-0.28.0.tar.gz]
> gunzip qpid-proton-0.28.0.tar.gz
> mkdir -p qpid-proton-0.28.0/build && pushd qpid-proton-0.28.0/build && cmake
> .. && make all && popd
> # Replace and edit example *qpid-proton-0.28.0/cpp/examples/simple_recv.cpp*
> with the one attached
> # Build again
> cd qpid-proton-0.28.0/build
> make
> # Break the broker
> ./cpp/examples/simple_recv & ./cpp/examples/simple_recv
> Connection error
> {color:#ffab00}^C <= Hit Ctrl+C to kill process{color}
> # {color:#172b4d}If CPU usage didn't increased, find the PID of the first
> simple_recv process using ps-ef | grep simple_recv and kill it using kill -9
> PID.{color}
> *Analysis*
> CPU usage rises when connection is dropped on the client side or when network
> is broken between client and broker. The main point is that client isn't well
> behaved and connection shouldn't be closed correctly.
> On broker side connection becomes "orphaned": it is still maintained by
> broker, but no real reading / writing is performed. Following method calls
> are performed in an endless loop for each "orphaned" connection:
> SelectorThread.performSelect()
> SelectorThread.ConnectionProcessor.processConnection()
> NetworkConnectionScheduler.processConnection()
> NonBlockingConnection.doWork()
> As there nothing physically read or written, both methods
> NonBlockingConnection.doRead() and NonBlockingConnection.doWrite() execute
> very fast (several milliseconds) without any blocking processes and after
> that connection is immediately rescheduled for processing in
> NetworkConnectionScheduler. After that loop repeats.
> As the connection lifecycle is normal, there is logged nothing unusual or
> suspicious (nothing is seen in log at all).
> In thread dump (see attachment) there is seen, that utilized are mostly
> thread with names virtualhost-default-iopool-XX. Typical stacktrace looks
> like following:
> {noformat}
> "virtualhost-default-iopool-39" #92 prio=5 os_prio=0 tid=0x00007f47ec335800
> nid=0x37196 waiting on condition
> [0x00007f476a4e3000]"virtualhost-default-iopool-39" #92 prio=5 os_prio=0
> tid=0x00007f47ec335800 nid=0x37196 waiting on condition [0x00007f476a4e3000]
> java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native
> Method) - parking to wait for <0x00000000f39105d0> (a
> java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at
> java.util.concurrent.locks.LockSupport.park(LockSupport.java:175) at
> java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
> at
> java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
> at
> org.apache.qpid.server.transport.SelectorThread.run(SelectorThread.java:532)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
> at
> org.apache.qpid.server.bytebuffer.QpidByteBufferFactory.lambda$null$0(QpidByteBufferFactory.java:464)
> at
> org.apache.qpid.server.bytebuffer.QpidByteBufferFactory$$Lambda$18/422330142.run(Unknown
> Source) at java.lang.Thread.run(Thread.java:748)}
> {noformat}
> The main symptom of an error is rising CPU usage, which can reach up to 90%
> in case, when several connections are "orphaned". Additional factor leading
> to the problem is disabled keep-alive option for a connection or long
> keep-alive interval.
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