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https://issues.apache.org/jira/browse/CASSANDRA-12510?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15838217#comment-15838217
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Nick Bailey commented on CASSANDRA-12510:
-----------------------------------------
Removing the no argument version of decommission here was a breaking API change
that we should have done in a major release (which tick tock makes weird but
still). This is more of an informational comment than anything because I'm not
sure it's worth fixing now, but just a reminder to keep an eye out for breaking
JMX changes.
> Disallow decommission when number of replicas will drop below configured RF
> ---------------------------------------------------------------------------
>
> Key: CASSANDRA-12510
> URL: https://issues.apache.org/jira/browse/CASSANDRA-12510
> Project: Cassandra
> Issue Type: Improvement
> Components: Streaming and Messaging
> Environment: C* version 3.3
> Reporter: Atin Sood
> Assignee: Kurt Greaves
> Priority: Minor
> Labels: lhf
> Fix For: 3.12
>
> Attachments: 12510-3.x.patch, 12510-3.x-v2.patch
>
>
> Steps to replicate :
> - Create a 3 node cluster in DC1 and create a keyspace test_keyspace with
> table test_table with replication strategy NetworkTopologyStrategy , DC1=3 .
> Populate some data into this table.
> - Add 5 more nodes to this cluster, but in DC2. Also do not alter the
> keyspace to add the new DC2 to replication (this is intentional and the
> reason why the bug shows up). So the desc keyspace should still list
> NetworkTopologyStrategy with DC1=3 as RF
> - As expected, this will now be a 8 node cluster with 3 nodes in DC1 and 5 in
> DC2
> - Now start decommissioning the nodes in DC1. Note that the decommission runs
> fine on all the 3 nodes, but since the new nodes are in DC2 and the RF for
> keyspace is restricted to DC1, the new 5 nodes won't get any data.
> - You will now end with the 5 node cluster which has no data from the
> decommissioned 3 nodes and hence ending up in data loss
> I do understand that this problem could have been avoided if we perform an
> alter stmt and add DC2 replication before adding the 5 nodes. But the fact
> that decommission ran fine on the 3 nodes on DC1 without complaining that
> there were no nodes to stream its data seems a little discomforting.
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