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https://issues.apache.org/jira/browse/CASSANDRA-6887?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Aleksey Yeschenko updated CASSANDRA-6887:
-----------------------------------------
Priority: Minor (was: Major)
> LOCAL_ONE read repair only does local repair, in spite of global digest
> queries
> -------------------------------------------------------------------------------
>
> Key: CASSANDRA-6887
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6887
> Project: Cassandra
> Issue Type: Bug
> Environment: Cassandra 2.0.6, x86-64 ubuntu precise
> Reporter: Duncan Sands
> Priority: Minor
> Fix For: 3.x
>
> Attachments: 6887-2.0.txt
>
>
> I have a cluster spanning two data centres. Almost all of the writing (and a
> lot of reading) is done in DC1. DC2 is used for running the occasional
> analytics query. Reads in both data centres use LOCAL_ONE. Read repair
> settings are set to the defaults on all column families.
> I had a long network outage between the data centres; it lasted longer than
> the hints window, so after it was over DC2 didn't have the latest
> information. Even after reading data many many times in DC2, the returned
> data was still out of date: read repair was not correcting it.
> I then investigated using cqlsh in DC2, with tracing on.
> What I saw was:
> - with consistency ONE, after about 10 read requests a digest request would
> be sent to many nodes (spanning both data centres), and the data in DC2 would
> be repaired.
> - with consistency LOCAL_ONE, after about 10 read requests a digest request
> would be sent to many nodes (spanning both data centres), but the data in DC2
> would not be repaired. This is in spite of digest requests being sent to
> DC1, as shown by the tracing.
> So it looks like digest requests are being sent to both data centres, but
> replies from outside the local data centre are ignored when using LOCAL_ONE.
> The same data is being queried all the time in DC1 with consistency
> LOCAL_ONE, but this didn't result in the data in DC2 being read repaired
> either. This is a slightly different case to what I described above: in that
> case the local node was out of date and the remote node had the latest data,
> while here it is the other way round.
> It could be argued that you don't want cross data centre read repair when
> using LOCAL_ONE. But then why bother sending cross data centre digest
> requests? And if only doing local read repair is how it is supposed to work
> then it would be good to document this somewhere.
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