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https://issues.apache.org/jira/browse/SOLR-14409?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17084714#comment-17084714
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Andrzej Bialecki commented on SOLR-14409:
-----------------------------------------
This patch illustrates the problem.
This may be a bug in {{AddReplicaSuggester}} or in {{Suggester.isLessSerious /
containsNewErrors}} .
{{AddReplicaSuggester}} tries all nodes but they all produce new violations -
except for the one that already has a violation. So for all other nodes the
condition in {{AddReplicaSuggester:55 if (!containsNewErrors(errs))}} is always
false because they produce new errors. As a side-effect of this the variable
{{leastSeriousViolation}} is never assigned.
Finally, for the node that already has a violation the change does not produce
a new violation, it only increases the severity of the existing one - but the
code doesn't check this because {{leastSeriousViolation}} is null, so it treats
the current error as the least serious.
This may be the conceptual problem here - if there were no other errors then
shouldn't the current errors be the most serious? but in this case there's
already a pre-existing violation on this node so perhaps the
{{leastSeriousViolation}} should always be initialized with the existing
violations? (I tried it and many unit tests started failing...)
> Existing violations allow bypassing policy rules when adding new replicas
> -------------------------------------------------------------------------
>
> Key: SOLR-14409
> URL: https://issues.apache.org/jira/browse/SOLR-14409
> Project: Solr
> Issue Type: Bug
> Security Level: Public(Default Security Level. Issues are Public)
> Components: AutoScaling
> Affects Versions: master (9.0), 8.5, 8.6
> Reporter: Andrzej Bialecki
> Assignee: Andrzej Bialecki
> Priority: Major
> Attachments: SOLR-14409.patch
>
>
> Steps to reproduce:
> * start with an empty cluster policy.
> * create a collection with as many replicas as there are nodes.
> * add one more replica to any node. Now this node has two replicas, all
> other nodes have one.
> * define the following cluster policy:
> {code:java}
> { 'set-cluster-policy': [ {'replica': '<2', 'shard': '#ANY', 'node': '#ANY',
> 'strict': true} ] } {code}
> This automatically creates a violation because of the existing layout.
> * try adding one more replica. This should fail because no node satisfies
> the rules (there must be at most 1 replica per node). However, the command
> succeeds and adds replica to the node that already has 2 replicas, which
> clearly violates the policy and makes matters even worse.
>
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