[jboss-jira] [JBoss JIRA] (JGRP-1379) Make merging more scalable / robust
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https://issues.jboss.org/browse/JGRP-1379?page=com.atlassian.jira.plugin....
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Bela Ban commented on JGRP-1379:
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MERGE2.merge_fast compounds the problem if we have a large cluster and have a lot of
subpartitions, e.g. after powering the switch off and then on again.
In the worst case, merge_fast causes N * N discovery requests to be sent in a cluster of N
nodes.
We should probably turn merge_fast off in large clusters (or do it dynamically with
ergonomics), or set merge_fast dynamically, based on the discovery traffic (rate of
discovery requests and responses)
Make merging more scalable / robust
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Key: JGRP-1379
URL: https://issues.jboss.org/browse/JGRP-1379
Project: JGroups
Issue Type: Task
Reporter: Bela Ban
Assignee: Bela Ban
Fix For: 3.0
Make the MERGE2/GMS/Merger code more robust and scale better in large clusters.
- While a merge is going on, stop sending out discovery requests. This reduces
unnecessary traffic, especially in large clusters where discovery responses include the
entire view of a sub-cluster
- If we start a merge, or receive a MERGE-REQUEST, start a timer which cancels the merge
after <merge_timeout *2> milliseconds. This is similar to the MergeKiller code, and
prevents stale merges, e.g. by a crashed merge leader
- If we have merge participants A,B,C,D,E but A only receives merge responses from
itself, B and D, then don't cancel the merge, but instead proceed with merging A, B
and D. This is currently not done, but a merge is cancelled when we don't get
responses from every participant.
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