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https://issues.apache.org/jira/browse/SOLR-7569?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14964979#comment-14964979
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Shalin Shekhar Mangar commented on SOLR-7569:
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Thanks Ishan.
# ForceLeaderTest.testReplicasInLIRNoLeader has a 5 second sleep, why? Isn't
waitForRecoveriesToFinish() enough?
# Similarly, ForceLeaderTest.testLeaderDown has a 15 second sleep for steady
state to be reached? What is this steady state, is there a better way than
waiting for an arbitrary amount of time? In general, Thread.sleep should be
avoided as much as possible as a way to reach steady state.
# Can you please add some javadocs on the various test methods describing the
scenario that they are test?
# minor nit - can you use assertEquals when testing equality of state etc
instead of assertTrue. The advantage with assertEquals is that it logs the
mismatched values in the exception messages.
# In OverseerCollectionMessageHandler, lirPath can never be null. The lir path
should probably be logged in debug rather than INFO.
{code}
// Clear out any LIR state
String lirPath =
overseer.getZkController().getLeaderInitiatedRecoveryZnodePath(collection,
sliceId);
if (lirPath != null && zkStateReader.getZkClient().exists(lirPath, true))
{
StringBuilder sb = new StringBuilder();
zkStateReader.getZkClient().printLayout(lirPath, 4, sb);
log.info("Cleaning out LIR data, which was: " + sb);
zkStateReader.getZkClient().clean(lirPath);
}
{code}
# There's no need to send an empty string as the role while publishing the
state of the replica.
# minor nit - you can compare enums directly using == instead of .equals
# Referring to the following, what is the thinking behind it? when can this
happen? is there a test which specifically exercises this scenario? seems like
this can interfere with the leader election if the leader election was taking
some time?
{code}
// If we still don't have an active leader by now, it maybe possible that the
replica at the head of the election queue
// was the leader at some point and never left the queue, but got marked
as down. So, if the election queue is not empty,
// and the replica at the head of the queue is live, then mark it as a
leader.
{code}
> Create an API to force a leader election between nodes
> ------------------------------------------------------
>
> Key: SOLR-7569
> URL: https://issues.apache.org/jira/browse/SOLR-7569
> Project: Solr
> Issue Type: New Feature
> Components: SolrCloud
> Reporter: Shalin Shekhar Mangar
> Assignee: Shalin Shekhar Mangar
> Labels: difficulty-medium, impact-high
> Attachments: SOLR-7569.patch, SOLR-7569.patch, SOLR-7569.patch,
> SOLR-7569.patch, SOLR-7569.patch, SOLR-7569.patch, SOLR-7569.patch,
> SOLR-7569.patch, SOLR-7569.patch, SOLR-7569.patch,
> SOLR-7569_lir_down_state_test.patch
>
>
> There are many reasons why Solr will not elect a leader for a shard e.g. all
> replicas' last published state was recovery or due to bugs which cause a
> leader to be marked as 'down'. While the best solution is that they never get
> into this state, we need a manual way to fix this when it does get into this
> state. Right now we can do a series of dance involving bouncing the node
> (since recovery paths between bouncing and REQUESTRECOVERY are different),
> but that is difficult when running a large cluster. Although it is possible
> that such a manual API may lead to some data loss but in some cases, it is
> the only possible option to restore availability.
> This issue proposes to build a new collection API which can be used to force
> replicas into recovering a leader while avoiding data loss on a best effort
> basis.
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