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From "Sergio Bossa (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-9318) Bound the number of in-flight requests at the coordinator
Date Tue, 12 Jul 2016 19:35:20 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-9318?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15373547#comment-15373547
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Sergio Bossa commented on CASSANDRA-9318:
-----------------------------------------

[~jbellis],

bq. Put another way: we do NOT want to limit performance to the slowest node in a set of replicas.
That is kind of the opposite of the redundancy we want to provide.

What if we tailored the algorithm to only:
* Rate limit if CL replicas are below the high threshold.
* Throw exception if CL replicas are below the low threshold.

By doing so, C* would behave the same provided at least CL replicas behave normally.

> Bound the number of in-flight requests at the coordinator
> ---------------------------------------------------------
>
>                 Key: CASSANDRA-9318
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9318
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Local Write-Read Paths, Streaming and Messaging
>            Reporter: Ariel Weisberg
>            Assignee: Sergio Bossa
>         Attachments: 9318-3.0-nits-trailing-spaces.patch, backpressure.png, limit.btm,
no_backpressure.png
>
>
> It's possible to somewhat bound the amount of load accepted into the cluster by bounding
the number of in-flight requests and request bytes.
> An implementation might do something like track the number of outstanding bytes and requests
and if it reaches a high watermark disable read on client connections until it goes back below
some low watermark.
> Need to make sure that disabling read on the client connection won't introduce other
issues.



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