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https://issues.apache.org/jira/browse/CASSANDRA-17342?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Brandon Williams reassigned CASSANDRA-17342:
--------------------------------------------
Assignee: Brandon Williams
> Performance problem for node restart with incremental range repairs
> -------------------------------------------------------------------
>
> Key: CASSANDRA-17342
> URL: https://issues.apache.org/jira/browse/CASSANDRA-17342
> Project: Cassandra
> Issue Type: Bug
> Components: Consistency/Repair
> Reporter: Paul Chandler
> Assignee: Brandon Williams
> Priority: Normal
> Fix For: 4.0.x
>
> Attachments: BulkRepairStateTest.java,
> IncrementalRepairStartupTest.java, LocalSessions.java, RepairedState.java
>
>
> There is a performance problem when restarting cassandra for clusters doing
> incremental repairs with range repairs.
> We have clusters with 16 vnodes per node, and are splitting each vnode into
> 100 ranges, this causes a node to take over 30 minutes to process the data
> stored in the system.repairs table before the node can restart. Even when we
> reduce this to 10 ranges per vnode this still takes 2 minutes to process. The
> cluster has 22 keyspaces and a rf of 3, this creates around 8100 records in
> the system.repairs table.
>
> The problem seems to occur in the
> org.apache.cassandra.repair.consistent.RepairState class where the add method
> re processes the complete list, including sorting, every time a new Range is
> added. This leads is an exponential growth in processing time, this is
> demonstrated in the attached unit test.
>
> I have created a change, that collects the data read in from the
> system.repairs table, in the
> org.apache.cassandra.repair.consistent.LocalSessions class, before processing
> it as a group at the end, this reduces the processing time to a couple of
> seconds even for the 100 range version.
>
> This is my first attempt at changing the cassandra code, so I am in need of a
> mentor to help me with the process, and validate what I have done.
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