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From "Philip Thompson (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-11804) Read request at proper CL returns ReadTimeout occasionally
Date Tue, 17 May 2016 01:10:12 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-11804?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Philip Thompson updated CASSANDRA-11804:
----------------------------------------
    Reproduced In: 3.4
    Fix Version/s: 3.x

> Read request at proper CL returns ReadTimeout occasionally
> ----------------------------------------------------------
>
>                 Key: CASSANDRA-11804
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-11804
>             Project: Cassandra
>          Issue Type: Bug
>         Environment: C* 3.4 | Ruby-driver 3.0-rc2
>            Reporter: Kishan Karunaratne
>             Fix For: 3.x
>
>
> I have a 3-node cluster with a keyspace with RF=3, with some data inserted. I'm using
a DowngradingConsistency retry policy on the client. Performing a query at CL=ALL with one
node blocked (ccm pause/SIGSTOP), the query fails and returns a ReadTimeout to the client
as expected. The following is in the debug log:
> {noformat}
> ReadCallback.java:126 - Timed out; received 2 of 3 responses (including data)
> {noformat}
> Now, the driver automatically retries once, and in this case at QUORUM.  The client receives
a ReadTimeout once more: "Cassandra::Errors::ReadTimeoutError: Operation timed out - received
only 1 responses." This ReadTimeout should not have happened because we still have 2 good
nodes/hosts to retrieve data from. This is in the debug log:
> {noformat}
> ReadCallback.java:126 - Timed out; received 1 of 2 responses (including data)
> {noformat}
> The weird part is that the query does occasionally succeed (at QUORUM), I'd say <
50% of the time. I did the same experiment with two nodes blocked and I get "Cassandra::Errors::ReadTimeoutError:
Operation timed out - received only 0 responses.":
> {noformat}
> ReadCallback.java:126 - Timed out; received 1 of 3 responses (including data)
> ReadCallback.java:126 - Timed out; received 0 of 1 responses
> {noformat}
> I expect this query to have succeeded at ONE, because there is one good node left (and
it's the one used as the coordinator node). In both cases, I feel like the coordinator node
doesn't count itself as a replica for the CL.



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