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From "Tyler Hobbs (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6731) Requests unnecessarily redirected with CL=ONE
Date Wed, 19 Feb 2014 23:24:21 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6731?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13906264#comment-13906264
] 

Tyler Hobbs commented on CASSANDRA-6731:
----------------------------------------

[~enigmacurry] I think you may be seeing speculative retry.  If I set dynamic_snitch=false,
rrc=0, and speculative_retry=None, I get no redirected queries.

If I leave dynamic_snitch=true with the other DES settings at their defaults, rrc=0, and speculative_retry=None,
I see roughly 17% of requests (170 of 1000) go to nodes other than the coordinator.  That
seems high, but this is all in ccm, so remote DCs have the same latency.  Perhaps we should
do some realistic testing to consider raising the default badness_threshold?

> Requests unnecessarily redirected with CL=ONE
> ---------------------------------------------
>
>                 Key: CASSANDRA-6731
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6731
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>         Environment: Linux
>            Reporter: Aris Prassinos
>            Assignee: Tyler Hobbs
>            Priority: Minor
>             Fix For: 2.0.6
>
>         Attachments: 6731.traces.txt, ticket_6731.py
>
>
> Three-node cluster with RF=3. All data currently in sync.
> Network topology strategy. Each node defined to be on a different rack.
> endpoint_snitch: PropertyFileSnitch
> dynamic_snitch_update_interval_in_ms: 100
> dynamic_snitch_reset_interval_in_ms: 600000
> dynamic_snitch_badness_threshold: 0
> All tables defined with read_repair_chance=0
> From cqlsh when querying with Consistency=ONE tracing shows that requests get frequently
redirected to other nodes even though the local node has the data.
> There is no other activity on the cluster besides my test queries.



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