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From "Brandon Williams (Updated) (JIRA)" <>
Subject [jira] [Updated] (CASSANDRA-3722) Send Hints to Dynamic Snitch when Compaction or repair is going on for a node.
Date Fri, 30 Mar 2012 18:28:28 GMT


Brandon Williams updated CASSANDRA-3722:

    Attachment: 3722-v4.txt

I think requests pending just isn't a good measure, especially for a multi-dc setup.  Instead
what we can do is penalize hosts based on the last time they replied, with a cap of the update
interval.  This way, if we aren't querying cross-dc, that dc is penalized, but within a reasonable
limit such that if the local reads get bad we'll exceed the threshold and go cross-dc if we
have to.  This seems to respond much better to my torture test of force-suspending a JVM,
but not long enough for the FD to kick in.
> Send Hints to Dynamic Snitch when Compaction or repair is going on for a node.
> ------------------------------------------------------------------------------
>                 Key: CASSANDRA-3722
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 1.1.0
>            Reporter: Vijay
>            Assignee: Vijay
>            Priority: Minor
>         Attachments: 0001-CASSANDRA-3722-A1-V2.patch, 0001-CASSANDRA-3722-A1.patch, 0001-CASSANDRA-3722-v3.patch,
0001-CASSANDRA-3723-A2-Patch.patch, 0001-Expose-SP-latencies-in-nodetool-proxyhistograms.txt,
> Currently Dynamic snitch looks at the latency for figuring out which node will be better
serving the requests, this works great but there is a part of the traffic sent to collect
this data... There is also a window when Snitch doesn't know about some major event which
are going to happen on the node (Node which is going to receive the data request).
> It would be great if we can send some sort hints to the Snitch so they can score based
on known events causing higher latencies.

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