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Posted to commits@cassandra.apache.org by "Benedict (JIRA)" <ji...@apache.org> on 2019/01/03 11:29:00 UTC
[jira] [Updated] (CASSANDRA-14855) Message Flusher scheduling fell
off the event loop, resulting in out of memory
[ https://issues.apache.org/jira/browse/CASSANDRA-14855?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Benedict updated CASSANDRA-14855:
---------------------------------
Component/s: (was: Legacy/Core)
Messaging/Client
> Message Flusher scheduling fell off the event loop, resulting in out of memory
> ------------------------------------------------------------------------------
>
> Key: CASSANDRA-14855
> URL: https://issues.apache.org/jira/browse/CASSANDRA-14855
> Project: Cassandra
> Issue Type: Bug
> Components: Messaging/Client
> Reporter: Sumanth Pasupuleti
> Assignee: Sumanth Pasupuleti
> Priority: Major
> Labels: pull-request-available
> Fix For: 3.0.18
>
> Attachments: blocked_thread_pool.png, cpu.png, eventloop_scheduledtasks.png, flusher running state.png, heap.png, heap_dump.png, read_latency.png
>
> Time Spent: 20m
> Remaining Estimate: 0h
>
> We recently had a production issue where about 10 nodes in a 96 node cluster ran out of heap.
> From heap dump analysis, I believe there is enough evidence to indicate `queued` data member of the Flusher got too big, resulting in out of memory.
> Below are specifics on what we found from the heap dump (relevant screenshots attached):
> * non-empty "queued" data member of Flusher having retaining heap of 0.5GB, and multiple such instances.
> * "running" data member of Flusher having "true" value
> * Size of scheduledTasks on the eventloop was 0.
> We suspect something (maybe an exception) caused the Flusher running state to continue to be true, but was not able to schedule itself with the event loop.
> Could not find any ERROR in the system.log, except for following INFO logs around the incident time.
> {code:java}
> INFO [epollEventLoopGroup-2-4] 2018-xx-xx xx:xx:xx,592 Message.java:619 - Unexpected exception during request; channel = [id: 0x8d288811, L:/xxx.xx.xxx.xxx:7104 - R:/xxx.xx.x.xx:18886]
> io.netty.channel.unix.Errors$NativeIoException: readAddress() failed: Connection timed out
> at io.netty.channel.unix.Errors.newIOException(Errors.java:117) ~[netty-all-4.0.44.Final.jar:4.0.44.Final]
> at io.netty.channel.unix.Errors.ioResult(Errors.java:138) ~[netty-all-4.0.44.Final.jar:4.0.44.Final]
> at io.netty.channel.unix.FileDescriptor.readAddress(FileDescriptor.java:175) ~[netty-all-4.0.44.Final.jar:4.0.44.Final]
> at io.netty.channel.epoll.AbstractEpollChannel.doReadBytes(AbstractEpollChannel.java:238) ~[netty-all-4.0.44.Final.jar:4.0.44.Final]
> at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:926) ~[netty-all-4.0.44.Final.jar:4.0.44.Final]
> at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:397) [netty-all-4.0.44.Final.jar:4.0.44.Final]
> at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:302) [netty-all-4.0.44.Final.jar:4.0.44.Final]
> at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:131) [netty-all-4.0.44.Final.jar:4.0.44.Final]
> at io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory.java:144) [netty-all-4.0.44.Final.jar:4.0.44.Final]
> {code}
> I would like to pursue the following proposals to fix this issue:
> # ImmediateFlusher: Backport trunk's ImmediateFlusher ( [CASSANDRA-13651|https://issues.apache.org/jira/browse/CASSANDRA-13651] https://github.com/apache/cassandra/commit/96ef514917e5a4829dbe864104dbc08a7d0e0cec) to 3.0.x and maybe to other versions as well, since ImmediateFlusher seems to be more robust than the existing Flusher as it does not depend on any running state/scheduling.
> # Make "queued" data member of the Flusher bounded to avoid any potential of causing out of memory due to otherwise unbounded nature.
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