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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (CASSANDRA-9318) Bound the number of in-flight requests at the coordinator
Date Fri, 08 May 2015 20:37:02 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-9318?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14535449#comment-14535449
] 

Jonathan Ellis edited comment on CASSANDRA-9318 at 5/8/15 8:36 PM:
-------------------------------------------------------------------

bq. It currently bounds the number of in flight requests low enough

Where?  Are you talking about the hint limit?

bq. I thought if we were capable of writing a hint we had to do it. 

The coordinator must write a hint *if a replica times out after it sends the mutation out.*
 (Because otherwise we leave the client wondering what state the cluster is left in; it might
be on all replicas, or on none.)  No hint is written for UnavailableException or OverloadedException,
because we can guarantee the state -- it is on no replicas.


was (Author: jbellis):
bq. It currently bounds the number of in flight requests low enough

Where?  Are you talking about the hint limit?

bq. I thought if we were capable of writing a hint we had to do it. 

We have to write a hint *if we send the mutation off to the replicas.*  (Because otherwise
we leave the client wondering what state the cluster is left in; it might be on all replicas,
or on none.)  No hint is written for UnavailableException or OverloadedException, because
we can guarantee the state -- it is on no replicas.

> 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
>            Reporter: Ariel Weisberg
>            Assignee: Ariel Weisberg
>             Fix For: 2.1.x
>
>
> 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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