[jira] [Commented] (CASSANDRA-3722) Send Hints to Dynamic Snitch when Compaction or repair is going on for a node.

["Pavel Yaskevich (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-3722?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13219639#comment-13219639 ] 

Pavel Yaskevich commented on CASSANDRA-3722:
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Also maintaining a kind of normalized load statistics for each node in the combination with pending requests could give a better view of what is going on on the node e.g. load is <= 0.5 but we have a big pending queue for/on the node - that could mean network failure. For the statistic we can assign each of the sub-routines "load impact" factor e.g. compaction 0.3, scrub - 0.2, read - 0.01, we can set the load threshold for "overloaded" nodes e.g. 0.85 (which could be adjusted at runtime) and sort hosts accordingly to their load + pending request statistics which would make penalizing hosts more precise. Obviously some normalization should be done because clusters won't always have nodes with identical processing capabilities (network, hardware etc.).
                
> Send Hints to Dynamic Snitch when Compaction or repair is going on for a node.
> ------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-3722
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3722
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 1.1.0
>            Reporter: Vijay
>            Assignee: Vijay
>            Priority: Minor
>
> 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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