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From "Aleksey Yeschenko (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-11432) Counter values become under-counted when running repair.
Date Tue, 10 May 2016 17:05:13 GMT


Aleksey Yeschenko commented on CASSANDRA-11432:

You might be right, though I don't see it as a counters problem at this point (and there isn't
much to be done here, either, so I'll be closing the ticket).

That said, some improvements that might help here eventually:
- CASSANDRA-10862, to reduce the number of referenced sstables during reads after streaming,
will affect the read before write portion of counter writes
- CASSANDRA-9811, when implemented, will allow to eliminate some of the sstables on the read-before-write
path, if any sstable X has its highest timestamp that is lower than the last-read global shard's
for the node

> Counter values become under-counted when running repair.
> --------------------------------------------------------
>                 Key: CASSANDRA-11432
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Dikang Gu
>            Assignee: Aleksey Yeschenko
> We are experimenting Counters in Cassandra 2.2.5. Our setup is that we have 6 nodes,
across three different regions, and in each region, the replication factor is 2. Basically,
each nodes holds a full copy of the data.
> We are writing to cluster with CL = 2, and reading with CL = 1. 
> When are doing 30k/s counter increment/decrement per node, and at the meanwhile, we are
double writing to our mysql tier, so that we can measure the accuracy of C* counter, compared
to mysql.
> The experiment result was great at the beginning, the counter value in C* and mysql are
very close. The difference is less than 0.1%. 
> But when we start to run the repair on one node, the counter value in C* become much
less than the value in mysql,  the difference becomes larger than 1%.
> My question is that is it a known problem that the counter value will become under-counted
if repair is running? Should we avoid running repair for counter tables?
> Thanks. 

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