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https://issues.apache.org/jira/browse/CASSANDRA-14503?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16588759#comment-16588759
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Jason Brown commented on CASSANDRA-14503:
-----------------------------------------
Working on a solution that will also resolve the problems [~sbtourist] raised
with CASSANDRA-14507. I've spoken with some of the netty maintainers and
they've given me some solid advice about to rework
{{OutboubndMessageConnection}}.
> Internode connection management is race-prone
> ---------------------------------------------
>
> Key: CASSANDRA-14503
> URL: https://issues.apache.org/jira/browse/CASSANDRA-14503
> Project: Cassandra
> Issue Type: Bug
> Components: Streaming and Messaging
> Reporter: Sergio Bossa
> Assignee: Jason Brown
> Priority: Major
>
> Following CASSANDRA-8457, internode connection management has been rewritten
> to rely on Netty, but the new implementation in
> {{OutboundMessagingConnection}} seems quite race prone to me, in particular
> on those two cases:
> * {{#finishHandshake()}} racing with {{#close()}}: i.e. in such case the
> former could run into an NPE if the latter nulls the {{channelWriter}} (but
> this is just an example, other conflicts might happen).
> * Connection timeout and retry racing with state changing methods:
> {{connectionRetryFuture}} and {{connectionTimeoutFuture}} are cancelled when
> handshaking or closing, but there's no guarantee those will be actually
> cancelled (as they might be already running), so they might end up changing
> the connection state concurrently with other methods (i.e. by unexpectedly
> closing the channel or clearing the backlog).
> Overall, the thread safety of {{OutboundMessagingConnection}} is very
> difficult to assess given the current implementation: I would suggest to
> refactor it into a single-thread model, where all connection state changing
> actions are enqueued on a single threaded scheduler, so that state
> transitions can be clearly defined and checked.
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