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From "Christian Esken (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-13265) Communication breakdown in OutboundTcpConnection
Date Tue, 28 Feb 2017 09:50:45 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-13265?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15887685#comment-15887685
] 

Christian Esken commented on CASSANDRA-13265:
---------------------------------------------

I see your argument. On larger clusters this may get problematic. Lets evaluate different
solutions:
- Offload expiration to a "random" regular Thread, but only a single one. If one Thread already
expires ...
 --- ... let the other Threads continue
 --- ... let the other Threads wait
- Go with your idea of an "Expiration Thread Pool"

Please see the attached Thread Dump to see which Threads are blocking. Mainly they are SharedPool-Worker
threads, that either do iterator.remove() or iterator.next().
{code}
"SharedPool-Worker-294" #587 daemon prio=5 os_prio=0 tid=0x00007fb69b11e260 nid=0x6090 waiting
on condition [0x00007fb162c0e000]
   java.lang.Thread.State: WAITING (parking)
        at sun.misc.Unsafe.park(Native Method)
        - parking to wait for  <0x000000023a426218> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)
        at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:870)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1199)
        at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:209)
        at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:285)
        at java.util.concurrent.LinkedBlockingQueue.fullyLock(LinkedBlockingQueue.java:225)
        at java.util.concurrent.LinkedBlockingQueue$Itr.remove(LinkedBlockingQueue.java:840)
        at org.apache.cassandra.net.OutboundTcpConnection.expireMessages(OutboundTcpConnection.java:555)
        at org.apache.cassandra.net.OutboundTcpConnection.enqueue(OutboundTcpConnection.java:165)
        at org.apache.cassandra.net.MessagingService.sendOneWay(MessagingService.java:771)
        at org.apache.cassandra.net.MessagingService.sendReply(MessagingService.java:744)
        at org.apache.cassandra.hints.HintVerbHandler.reply(HintVerbHandler.java:99)
        at org.apache.cassandra.hints.HintVerbHandler.doVerb(HintVerbHandler.java:94)
        at org.apache.cassandra.net.MessageDeliveryTask.run(MessageDeliveryTask.java:67)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
        at org.apache.cassandra.concurrent.AbstractLocalAwareExecutorService$FutureTask.run(AbstractLocalAwareExecutorService.java:164)
        at org.apache.cassandra.concurrent.AbstractLocalAwareExecutorService$LocalSessionFutureTask.run(AbstractLocalAwareExecutorService.java:136)
        at org.apache.cassandra.concurrent.SEPWorker.run(SEPWorker.java:105)
        at java.lang.Thread.run(Thread.java:745)
{code}

{code}
"SharedPool-Worker-295" #590 daemon prio=5 os_prio=0 tid=0x00007fb69b1135b0 nid=0x608d waiting
on condition [0x00007fb162cd1000]
   java.lang.Thread.State: WAITING (parking)
        at sun.misc.Unsafe.park(Native Method)
        - parking to wait for  <0x000000023a426218> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)
        at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:870)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1199)
        at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:209)
        at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:285)
        at java.util.concurrent.LinkedBlockingQueue.fullyLock(LinkedBlockingQueue.java:225)
        at java.util.concurrent.LinkedBlockingQueue$Itr.next(LinkedBlockingQueue.java:823)
        at org.apache.cassandra.net.OutboundTcpConnection.expireMessages(OutboundTcpConnection.java:550)
        at org.apache.cassandra.net.OutboundTcpConnection.enqueue(OutboundTcpConnection.java:165)
        at org.apache.cassandra.net.MessagingService.sendOneWay(MessagingService.java:771)
        at org.apache.cassandra.net.MessagingService.sendReply(MessagingService.java:744)
        at org.apache.cassandra.hints.HintVerbHandler.reply(HintVerbHandler.java:99)
        at org.apache.cassandra.hints.HintVerbHandler.doVerb(HintVerbHandler.java:94)
        at org.apache.cassandra.net.MessageDeliveryTask.run(MessageDeliveryTask.java:67)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
        at org.apache.cassandra.concurrent.AbstractLocalAwareExecutorService$FutureTask.run(AbstractLocalAwareExecutorService.java:164)
        at org.apache.cassandra.concurrent.AbstractLocalAwareExecutorService$LocalSessionFutureTask.run(AbstractLocalAwareExecutorService.java:136)
        at org.apache.cassandra.concurrent.SEPWorker.run(SEPWorker.java:105)
        at java.lang.Thread.run(Thread.java:745)
{code}

> Communication breakdown in OutboundTcpConnection
> ------------------------------------------------
>
>                 Key: CASSANDRA-13265
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-13265
>             Project: Cassandra
>          Issue Type: Bug
>         Environment: Cassandra 3.0.9
> Java HotSpot(TM) 64-Bit Server VM version 25.112-b15 (Java version 1.8.0_112-b15)
> Linux 3.16
>            Reporter: Christian Esken
>            Assignee: Christian Esken
>         Attachments: cassandra.pb-cache4-dus.2017-02-17-19-36-26.chist.xz, cassandra.pb-cache4-dus.2017-02-17-19-36-26.td.xz
>
>
> I observed that sometimes a single node in a Cassandra cluster fails to communicate to
the other nodes. This can happen at any time, during peak load or low load. Restarting that
single node from the cluster fixes the issue.
> Before going in to details, I want to state that I have analyzed the situation and am
already developing a possible fix. Here is the analysis so far:
> - A Threaddump in this situation showed  324 Threads in the OutboundTcpConnection class
that want to lock the backlog queue for doing expiration.
> - A class histogram shows 262508 instances of OutboundTcpConnection$QueuedMessage.
> What is the effect of it? As soon as the Cassandra node has reached a certain amount
of queued messages, it starts thrashing itself to death. Each of the Thread fully locks the
Queue for reading and writing by calling iterator.next(), making the situation worse and worse.
> - Writing: Only after 262508 locking operation it can progress with actually writing
to the Queue.
> - Reading: Is also blocked, as 324 Threads try to do iterator.next(), and fully lock
the Queue
> This means: Writing blocks the Queue for reading, and readers might even be starved which
makes the situation even worse.
> -----
> The setup is:
>  - 3-node cluster
>  - replication factor 2
>  - Consistency LOCAL_ONE
>  - No remote DC's
>  - high write throughput (100000 INSERT statements per second and more during peak times).
>  



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