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https://issues.apache.org/jira/browse/IMPALA-13253?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17869039#comment-17869039
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Joe McDonnell commented on IMPALA-13253:
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The AWS LB has an idle time limit of 350 seconds that does not explicitly
notify either end that the connection is dead:
[https://aws.amazon.com/blogs/networking-and-content-delivery/introducing-configurable-idle-timeout-for-connection-tracking/]
The libkeepalive library can be used to force a program to use TCP keepalive
without needing to recompile it:
[https://tldp.org/HOWTO/TCP-Keepalive-HOWTO/addsupport.html]
Testing using libkeepalive and iptables shows that it behaves as expected: It
can handle situations where packets are dropped or rejected. In a cluster that
uses the AWS LB, this can be set to have a keepalive time of 400 seconds to
very quickly detect and close connections that AWS LB considers idle.
I think keepalive should be on by default.
> Add option to use TCP keepalives for client connections
> -------------------------------------------------------
>
> Key: IMPALA-13253
> URL: https://issues.apache.org/jira/browse/IMPALA-13253
> Project: IMPALA
> Issue Type: Task
> Components: Backend, Clients
> Affects Versions: Impala 4.5.0
> Reporter: Joe McDonnell
> Priority: Blocker
>
> A client can be disconnected without explicitly closing its TCP connection.
> This can happen if the client machine resets or there is a network
> disruption. In particular, load balancers can have an idle time that results
> in a connection becoming invalid. Impala can't really guarantee that the
> client will properly tear down its connection and the Impala side resources
> will be released.
> TCP keepalive would allow Impala to detect dead clients and close the
> connection. It also can prevent a load balancer from seeing the connection as
> idle. This can be important for clients that hold connections in a pool.
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