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https://issues.apache.org/jira/browse/SOLR-7932?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14698590#comment-14698590
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Varun Thacker commented on SOLR-7932:
-------------------------------------
{code}
boolean isFullCopyNeeded = IndexDeletionPolicyWrapper
.getCommitTimestamp(commit) >= latestVersion
|| commit.getGeneration() >= latestGeneration || forceReplication;
{code}
I think we can just change it to: {{commit.getGeneration() >= latestGeneration
|| forceReplication}} .
Comparing timestamps would have been valid for master slave when the actual
index was rsynced and hence the commit timestamp would have been the same. And
the new check would not break master slave either since the commit generation
would be the same as well.
{code}
if (!forceReplication && IndexDeletionPolicyWrapper.getCommitTimestamp(commit)
== latestVersion) {
//master and slave are already in sync just return
LOG.info("Slave in sync with master.");
successfulInstall = true;
return true;
}
{code}
This should also check with the generation numbers I guess. This check is only
required in the master slave architecture. In cloud mode we would never call
IndexFetcher unless we wanted to replicate.
> Solr replication relies on timestamps to sync across machines
> -------------------------------------------------------------
>
> Key: SOLR-7932
> URL: https://issues.apache.org/jira/browse/SOLR-7932
> Project: Solr
> Issue Type: Bug
> Components: replication (java)
> Reporter: Ramkumar Aiyengar
>
> Spinning off SOLR-7859, noticed there that wall time recorded as commit data
> on a commit to check if replication needs to be done. In IndexFetcher, there
> is this code:
> {code}
> if (!forceReplication &&
> IndexDeletionPolicyWrapper.getCommitTimestamp(commit) == latestVersion) {
> //master and slave are already in sync just return
> LOG.info("Slave in sync with master.");
> successfulInstall = true;
> return true;
> }
> {code}
> It appears as if we are checking wall times across machines to check if we
> are in sync, this could go wrong.
> Once a decision is made to replicate, we do seem to use generations instead,
> except for this place below checks both generations and timestamps to see if
> a full copy is needed..
> {code}
> // if the generation of master is older than that of the slave , it
> means they are not compatible to be copied
> // then a new index directory to be created and all the files need to
> be copied
> boolean isFullCopyNeeded = IndexDeletionPolicyWrapper
> .getCommitTimestamp(commit) >= latestVersion
> || commit.getGeneration() >= latestGeneration || forceReplication;
> {code}
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