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https://issues.apache.org/jira/browse/SSHD-348?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14242768#comment-14242768
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Hugo Arès commented on SSHD-348:
--------------------------------
More info on the stream-events command and why it's used:
stream-events command is used by anyone who wants to see in events hapenning on
the gerrit server in real time. The connection will not disconnect until the
client disconnect and every time an event is hapenning, client will receive the
event detail, one event per line.
The most common use case is for build tools to get notified when something
happens on Gerrit and trigger builds accordingly. The most common integration
(a least for our company) is Gerrit-Trigger, which is a Jenkins plugin.
Gerrit-Trigger is using jsch so this is why I only saw stuck threads with jsch
since almost all the stream-events command towards our Gerrit server are
initiated by Gerrit-Trigger.
> Some SSH threads get blocked in Object.wait() method forever
> ------------------------------------------------------------
>
> Key: SSHD-348
> URL: https://issues.apache.org/jira/browse/SSHD-348
> Project: MINA SSHD
> Issue Type: Bug
> Affects Versions: 0.10.0, 0.10.1, 0.11.0, 0.12.0, 0.13.0
> Environment: Gerrit Code Review 2.9.1 (SSHD 0.12.0)
> Gerrit Code Review 2.9.2 (SSHD 0.13.0)
> Gerrit Code Review 2.9.3 (Downgraded to SSHD 0.9)
> Reporter: David Ostrovsky
> Assignee: Guillaume Nodet
> Priority: Blocker
> Fix For: 0.14.0
>
> Attachments: 0001-Prepare-release-sshd-0.13.0-72f868e26.patch, diff
>
>
> This seems to be a regression started from 0.10.1.
> In Gerrit we have SSH commamds that returns immediately and so called
> stream-events command which keeps connection open until clients disconnect.
> Basically for days or weeks. This is used for example to inform CI system
> (jenkins) about events in gerrit, like new patch set upload etc.
> In Gerrit we have configurable "SSH-Stream-Worker" thread pool which is
> dedicated to the mentioned stream-events SSH command. The observed behaviour
> on latest SSHD release is that after some time all threads are stuck. They
> aren't stuck at the same time, but one after another untill at some time all
> threads are stuck and Gerrit must be restarted. Usually after one week. The
> stack dump of all such stuck thread are the same, see below. If we had a
> patch we could apply it to our production Gerrit instance and try if this
> helps.
> {code}
> "SSH-Stream-Worker-10" cpu=95400.00 [reset 95400.00] ms elapsed=146444.30
> [reset 146444.30] s allocated=5526700000 B (5.15 GB) [reset 5526700000 B
> (5.15 GB)] defined_classes=0
> io= file i/o: 15622752/0 B, net i/o: 0/0 B, files opened:0, socks opened:0
> [reset file i/o: 15622752/0 B, net i/o: 0/0 B, files opened:0, socks opened:0
> ]
> prio=10 tid=0x00007f54514df800 nid=0x1c71 / 7281 pthread-id=139999281374976
> in Object.wait() [_thread_blocked (_at_safepoint),
> stack(0x00007f541f5f6000,0x00007f541f6f7000)] [0x00007f541f6f5000]
> java.lang.Thread.State: WAITING (on object monitor)
> at java.lang.Object.wait(J)V(Native Method)
> - waiting on <0x00007f553aa530d0> (a
> org.apache.sshd.common.channel.Window)
> at java.lang.Object.wait()V(Object.java:503)
> at
> org.apache.sshd.common.channel.Window.waitForSpace()I(Window.java:148)
> - locked <0x00007f553aa530d0> (a org.apache.sshd.common.channel.Window)
> at
> org.apache.sshd.common.channel.ChannelOutputStream.flush()V(ChannelOutputStream.java:116)
> - locked <0x00007f553aa55060> (a
> org.apache.sshd.common.channel.ChannelOutputStream)
> at
> org.apache.sshd.common.channel.ChannelOutputStream.write([BII)V(ChannelOutputStream.java:84)
> - locked <0x00007f553aa55060> (a
> org.apache.sshd.common.channel.ChannelOutputStream)
> at sun.nio.cs.StreamEncoder.writeBytes()V(StreamEncoder.java:221)
> at sun.nio.cs.StreamEncoder.implFlushBuffer()V(StreamEncoder.java:291)
> at sun.nio.cs.StreamEncoder.implFlush()V(StreamEncoder.java:295)
> at sun.nio.cs.StreamEncoder.flush()V(StreamEncoder.java:141)
> - locked <0x00007f553aa7e258> (a java.io.OutputStreamWriter)
> at java.io.OutputStreamWriter.flush()V(OutputStreamWriter.java:229)
> at java.io.BufferedWriter.flush()V(BufferedWriter.java:254)
> - locked <0x00007f553aa7e258> (a java.io.OutputStreamWriter)
> at java.io.PrintWriter.flush()V(PrintWriter.java:320)
> - locked <0x00007f553aa7e210> (a java.io.BufferedWriter)
> at java.io.PrintWriter.checkError()Z(PrintWriter.java:357)
> at
> com.google.gerrit.sshd.commands.StreamEvents.writeEvents()V(StreamEvents.java:186)
> at
> com.google.gerrit.sshd.commands.StreamEvents.access$100(Lcom/google/gerrit/sshd/commands/StreamEvents;)V(StreamEvents.java:43)
> at
> com.google.gerrit.sshd.commands.StreamEvents$3.run()V(StreamEvents.java:82)
> at
> java.util.concurrent.Executors$RunnableAdapter.call()Ljava/lang/Object;(Executors.java:471)
> at java.util.concurrent.FutureTask.run()V(FutureTask.java:262)
> at
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(Ljava/util/concurrent/ScheduledThreadPoolExecutor$ScheduledFutureTask;)V(ScheduledThreadPoolExecutor.java:178)
> at
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run()V(ScheduledThreadPoolExecutor.java:292)
> at
> com.google.gerrit.server.git.WorkQueue$Task.run()V(WorkQueue.java:364)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(Ljava/util/concurrent/ThreadPoolExecutor$Worker;)V(ThreadPoolExecutor.java:1145)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run()V(ThreadPoolExecutor.java:615)
> at java.lang.Thread.run()V(Thread.java:812)
> {code}
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