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From "T Jake Luciani (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-13074) DynamicEndpointSnitch frequently no-ops through early exit in multi-datacenter situations
Date Thu, 22 Dec 2016 19:51:58 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-13074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15770939#comment-15770939
] 

T Jake Luciani commented on CASSANDRA-13074:
--------------------------------------------

Looks good and nice fine. Would it be possible to write a dtest to verify the multi-dc use
and avoid any future bugs?

> DynamicEndpointSnitch frequently no-ops through early exit in multi-datacenter situations
> -----------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-13074
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-13074
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Coordination
>            Reporter: Joel Knighton
>            Assignee: Joel Knighton
>             Fix For: 2.2.x, 3.0.x, 3.x, 4.x
>
>
> The DynamicEndpointSnitch attempts to use timings from nodes to route reads to better
performing nodes.
> In a multi-datacenter situation, timings will likely be empty for nodes outside of the
local datacenter, as you'll frequently only be doing local_quorum reads (or a lower consistency
level). In this case, the DES exits early and returns the subsnitch ordering. This means poorly
performing replicas will never be avoided, no matter how degraded they are.



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