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https://issues.apache.org/jira/browse/CASSANDRA-12256?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tyler Hobbs updated CASSANDRA-12256:
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Summary: Count entire coordinated request against timeout (was: Properly
respect the request timeouts)
> Count entire coordinated request against timeout
> ------------------------------------------------
>
> Key: CASSANDRA-12256
> URL: https://issues.apache.org/jira/browse/CASSANDRA-12256
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Sylvain Lebresne
> Assignee: Geoffrey Yu
> Fix For: 3.10
>
> Attachments: 12256-trunk-v1v2.diff, 12256-trunk-v2.txt,
> 12256-trunk.txt
>
>
> We have a number of {{request_timeout_*}} option, that probably every user
> expect to be an upper bound on how long the coordinator will wait before
> timeouting a request, but it's actually not always the case, especially for
> read requests.
> I believe we don't respect those timeout properly in at least the following
> cases:
> * On a digest mismatch: in that case, we reset the timeout for the data
> query, which means the overall query might take up to twice the configured
> timeout before timeouting.
> * On a range query: the timeout is reset for every sub-range that is queried.
> With many nodes and vnodes, a range query could span tons of sub-range and so
> a range query could take pretty much arbitrary long before actually
> timeouting for the user.
> * On short reads: we also reset the timeout for every short reads "retries".
> It's also worth noting that even outside those, the timeouts don't take most
> of the processing done by the coordinator (query parsing and CQL handling for
> instance) into account.
> Now, in all fairness, the reason this is this way is that the timeout
> currently are *not* timeout for the full user request, but rather how long a
> coordinator should wait on any given replica for any given internal query
> before giving up. *However*, I'm pretty sure this is not what user
> intuitively expect and want, *especially* in the context of CASSANDRA-2848
> where the goal is explicitely to have an upper bound on the query from the
> user point of view.
> So I'm suggesting we change how those timeouts are handled to really be
> timeouts on the whole user query.
> And by that I basically just mean that we'd mark the start of each query as
> soon as possible in the processing, and use that starting time as base in
> {{ReadCallback.await}} and {{AbstractWriteResponseHandler.get()}}. It won't
> be perfect in the sense that we'll still only possibly timeout during
> "blocking" operations, so typically if parsing a query takes more than your
> timeout, you still won't timeout until that query is sent, but I think that's
> probably fine in practice because 1) if you timeouts are small enough that
> this matter, you're probably doing it wrong and 2) we can totally improve on
> that later if needs be.
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