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Markus Dlugi edited comment on CASSANDRA-13754 at 8/31/17 7:38 AM:
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[~jjirsa], we are experiencing the same issue on Cassandra 3.11.0 and Netty
4.0.44. We have some custom triggers which create additional rows when
{{INSERT}} s on specific CFs are executed. When inserting a lot of data, the
Cassandra would constantly crash with {{OutOfMemoryError}} s. We analyzed a
heap dump and came to the same conclusion, which is that the instances of
{{FastThreadLocalThread}} were responsible for this behaviour. As a quick
workaround, we added a call to {{FastThreadLocal.removeAll()}} to our triggers,
which alleviates the problem for us.
It seems that there already was an issue once with {{FastThreadLocal}} s, as
described in CASSANDRA-13033, but apparently the change by [~snazy] in
CASSANDRA-13034 resurfaced the issue. For a proper fix, I think all
{{FastThreadLocalThread}} instances should call {{FastThreadLocal.removeAll()}}
when they are done with their work. A quick glance at the code indicates that
this affects the classes {{CompressedInputStream}} ,
{{StreamingInboundHandler}} , {{NamedThreadFactory}} and {{SEPWorker}}.
was (Author: markusdlugi):
[~jjirsa], we are experiencing the same issue on Cassandra 3.11.0 and Netty
4.0.44. We have some custom triggers which create additional rows when
{{INSERT}}s on specific CFs are executed. When inserting a lot of data, the
Cassandra would constantly crash with {{OutOfMemoryError}}s. We analyzed a heap
dump and came to the same conclusion, which is that the instances of
{{FastThreadLocalThread}} were responsible for this behaviour. As a quick
workaround, we added a call to {{FastThreadLocal.removeAll()}} to our triggers,
which alleviates the problem for us.
It seems that there already was an issue once with {{FastThreadLocal}}s, as
described in CASSANDRA-13033, but apparently the change by [~snazy] in
CASSANDRA-13034 resurfaced the issue. For a proper fix, I think all
{{FastThreadLocalThread}} instances should call {{FastThreadLocal.removeAll()}}
when they are done with their work. A quick glance at the code indicates that
this affects the classes {{CompressedInputStream}},
{{StreamingInboundHandler}}, {{NamedThreadFactory}} and {{SEPWorker}}.
> FastThreadLocal leaks memory
> ----------------------------
>
> Key: CASSANDRA-13754
> URL: https://issues.apache.org/jira/browse/CASSANDRA-13754
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Environment: Cassandra 3.11.0, Netty 4.0.44.Final, OpenJDK 8u141-b15
> Reporter: Eric Evans
> Fix For: 3.11.1
>
>
> After a chronic bout of {{OutOfMemoryError}} in our development environment,
> a heap analysis is showing that more than 10G of our 12G heaps are consumed
> by the {{threadLocals}} members (instances of {{java.lang.ThreadLocalMap}})
> of various {{io.netty.util.concurrent.FastThreadLocalThread}} instances.
> Reverting
> [cecbe17|https://git-wip-us.apache.org/repos/asf?p=cassandra.git;a=commit;h=cecbe17e3eafc052acc13950494f7dddf026aa54]
> fixes the issue.
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