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From "Sam Tunnicliffe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8479) Timeout Exception on Node Failure in Remote Data Center
Date Mon, 29 Jun 2015 07:27:05 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8479?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14605231#comment-14605231
] 

Sam Tunnicliffe commented on CASSANDRA-8479:
--------------------------------------------

[~eanujwa] the digest requests were sent to nodes in the remote DC because of the {{read_repair_chance}}
setting on the table. Read repair is orthogonal to the consistency level specified for the
request, so the fact that the client request was using {{LOCAL_QUORUM}} has no bearing here.
The CL determines which and how many replica responses the coordinator will wait for before
returning to the client, it doesn't have any effect on which replicas are sent digest requests
when a global read repair is triggered (and it cannot, by definition *global* read repair
implies *all* replicas). There is ongoing discussion on CASSANDRA-6887 about whether LOCAL
CLs should influence the replica set for global read repair. Rather than re-opening this,
perhaps you could add your voice to that conversation.

> Timeout Exception on Node Failure in Remote Data Center
> -------------------------------------------------------
>
>                 Key: CASSANDRA-8479
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8479
>             Project: Cassandra
>          Issue Type: Bug
>          Components: API, Core, Tools
>         Environment: Unix, Cassandra 2.0.11
>            Reporter: Amit Singh Chowdhery
>            Assignee: Sam Tunnicliffe
>            Priority: Minor
>         Attachments: TRACE_LOGS.zip
>
>
> Issue Faced :
> We have a Geo-red setup with 2 Data centers having 3 nodes each. When we bring down a
single Cassandra node down in DC2 by kill -9 <Cassandra-pid>, reads fail on DC1 with
TimedOutException for a brief amount of time (15-20 sec~).
> Reference :
> Already a ticket has been opened/resolved and link is provided below :
> https://issues.apache.org/jira/browse/CASSANDRA-8352
> Activity Done as per Resolution Provided :
> Upgraded to Cassandra 2.0.11 .
> We have two 3 node clusters in two different DCs and if one or more of the nodes go down
in one Data Center , ~5-10% traffic failure is observed on the other.
> CL: LOCAL_QUORUM
> RF=3



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