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https://issues.apache.org/jira/browse/CASSANDRA-5926?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sylvain Lebresne resolved CASSANDRA-5926.
-----------------------------------------
Resolution: Fixed
Let me re-close this since the committed did fix the original deadlock. It's
obviously now unfortunate that we're running into a netty bug, but since 1.2.9
has shipped, I've opened a separate issue (CASSANDRA-5955) to upgrade our
dependency.
> The native protocol server can deadlock
> ---------------------------------------
>
> Key: CASSANDRA-5926
> URL: https://issues.apache.org/jira/browse/CASSANDRA-5926
> Project: Cassandra
> Issue Type: Bug
> Reporter: Sylvain Lebresne
> Assignee: Sylvain Lebresne
> Fix For: 1.2.9
>
> Attachments: 5926.txt, stack
>
>
> Until CASSANDRA-5239 (i.e. since StorageProxy is blocking), the native
> protocol server needs to use a thread per request being processed. For that,
> it currently use a DebuggableThreadPoolExecutor, but with a limited queue.
> The rational being that we don't want to OOM if a client overwhelm the
> server. Rather, we prefer blocking (which DTPE gives us) on the submission of
> new request by the netty worker threads when all threads are busy.
> However, as it happens, when netty sends back a response to a query, there is
> cases where some events (technically, InterestChanged and WriteComplete
> events) are send up the pipeline. And those event are submitted on the
> request executor as other requests. Long story short, a request thread can
> end blocking on the submission to its own executor, hence deadlocking.
> The simplest solution is probably to reuse MemoryAwareThreadPoolExecutor from
> netty rather that our own DTPE as it also allow to block task submission when
> all threads are busy but knows not to block it's own internal events.
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