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From "Sylvain Lebresne (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-6194) speculative retry can sometimes violate consistency
Date Tue, 22 Oct 2013 17:10:44 GMT


Sylvain Lebresne commented on CASSANDRA-6194:

For the record, the error returned by the dtest is:
FAIL: short_read_reversed_test (consistency_test.TestConsistency)
Traceback (most recent call last):
  File "/home/mcmanus/Git/dtest-cassandra/", line 309, in short_read_reversed_test
    assert res[i][1] == 'value%d' % (5-i), 'Expecting value%d, got %s (%s)' % (5-i, res[i][1],
AssertionError: Expecting value5, got value8 ([[u'c000008', u'value8'], [u'c000005', u'value5'],
[u'c000004', u'value4']])

Ran 1 test in 130.035s

> speculative retry can sometimes violate consistency
> ---------------------------------------------------
>                 Key: CASSANDRA-6194
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>            Reporter: Brandon Williams
>            Assignee: Jonathan Ellis
>             Fix For: 2.0.2
>         Attachments: 6194.txt
> This is most evident with intermittent failures of the short_read dtests.  I'll focus
on short_read_reversed_test for explanation, since that's what I used to bisect.  This test
inserts some columns into a row, then deletes a subset, but it performs each delete on a different
node, with another node down (hints are disabled.)  Finally it reads the row back at QUORUM
and checks that it doesn't see any deleted columns, however with speculative retry on this
often fails.  I bisected this to the change that made 99th percentile SR the default reliably
by looping the test enough times at each iteration to be sure it was passing or failing.

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