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https://issues.apache.org/activemq/browse/AMQ-1993?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=47006#action_47006
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Filip Hanik commented on AMQ-1993:
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I am currently working on a test case so that you can see this in action.
In the real life the following way is the easiest to reproduce
Have a few machines, consumers and producers working with the same topic
On one consumer machine - pull out the network cord
This action causes the connection to be in "ESTABLISHED" state, since no RST or
FIN packets have been sent.
the Linux TCP implementation will then try to resend the packet 15 times
(default config) with 2min in between each retransmission.
During this time, the server will keep filling up the TCP send buffer in the
kernel, and when it is full, the thread will get stuck in
java.net.Socket.socketWrite0
because this thread also holds the lock on the topic, no other thread can
operate on the topic anymore
best
Filip
> Systems hang due to inability to timeout socket write operation
> ---------------------------------------------------------------
>
> Key: AMQ-1993
> URL: https://issues.apache.org/activemq/browse/AMQ-1993
> Project: ActiveMQ
> Issue Type: Bug
> Components: Broker
> Affects Versions: 5.1.0, 5.2.0
> Environment: Unix (Solaris and Linux tested)
> Reporter: Filip Hanik
> Priority: Critical
> Attachments: patch-1-threadname-filter.patch,
> patch-3-tcp-writetimeout.patch
>
>
> the blocking Java Socket API doesn't have a timeout on socketWrite
> invocations.
> This means, if a TCP session is dropped or terminated without RST or FIN
> packets, the operating system it left to eventually time out the session. On
> the linux kernel this timeout usually takes 15 to 30minutes.
> For this entire period, the AMQ server hangs, and producers and consumers are
> unable to use a topic.
> I have created two patches for this at the page:
> http://www.hanik.com/covalent/amq/index.html
> Let me show a bit more
> ---------------------------------
> "ActiveMQ Transport: tcp:///X.YYY.XXX.ZZZZ:2011" daemon prio=10
> tid=0x0000000055d39000 nid=0xc78 runnable
> [0x00000000447c9000..0x00000000447cac10]
> java.lang.Thread.State: RUNNABLE
> at java.net.SocketOutputStream.socketWrite0(Native Method)
> at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:92)
> This is a thread stuck in blocking IO, and can be stuck for 30 minutes during
> the kernel TCP retransmission attempts.
> Unfortunately the thread dump is very misleading since the name of the
> thread, is not the destination or even remotely related to the socket it is
> operating on.
> To mend this, a very simple (and configurable) ThreadNameFilter has been
> suggested to the patch, that appends the destination and helps the system
> administrator correctly identify the client that is about to receive data.
> -----------------------------------
> at org.apache.activemq.broker.region.Topic.dispatch(Topic.java:581)
> at org.apache.activemq.broker.region.Topic.doMessageSend(Topic.java:421)
> - locked <0x00002aaaec155818> (a
> org.apache.activemq.broker.region.Topic)
> at org.apache.activemq.broker.region.Topic.send(Topic.java:363)
> The lock being held at this issue unfortunately makes the entire Topic single
> threaded.
> When this lock is being held, no other clients (producers and consumers) can
> publish to/receive from this topic.
> And this lock can hold up to 30 minutes.
> I consider solving this single threaded behavior a 'feature enhancement' that
> should be handled separately from this bug. Because even if it is solved,
> threads still risk being stuck in socketWrite0 for dropped connections that
> still appear to be established.
> For this, I have implemented a socket timeout filter, based on a
> TransportFilter, this filter only times out connections that are actually
> writing data.
> The two patches are at:
> http://www.hanik.com/covalent/amq/patch-1-threadname-filter.patch
> http://www.hanik.com/covalent/amq/patch-3-tcp-writetimeout.patch
> the binary 0000.jar applies to both 5.1 and trunk and can be used today in
> existing environments.
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