cassandra-commits mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Christian Esken (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-13265) Epxiration in OutboundTcpConnection can block the reader Thread
Date Thu, 02 Mar 2017 14:34:45 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-13265?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15892332#comment-15892332
] 

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

bq. use System.nanoTime() instead of System.currentTimeMillis().
Agreed, {{System.nanoTime()}} is slightly better here. In real life it won't make a terrific
difference even with the worst clocks, but "_lets do things right"_. :-) . I never looked
up the native code for nanoTIme(), but I bet on Unix it uses the POSIX {{clock_gettime(CLOCK_MONOTONIC,
...)}}.

bq. I don't think we want to traverse the entire backlog. [...]
Your argument  "reasonably in ascendingascending timestamp order" makes sense, if all entries
would have the same expiration time. But the Verbs have different timeouts. Thus iterating
the whole Queue should be done, as in the worst case we will remove nothing even though most
entries are timed out.


> Epxiration in OutboundTcpConnection can block the reader Thread
> ---------------------------------------------------------------
>
>                 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).
>  



--
This message was sent by Atlassian JIRA
(v6.3.15#6346)

Mime
View raw message