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https://issues.apache.org/jira/browse/SOLR-4354?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13562690#comment-13562690
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Shalin Shekhar Mangar commented on SOLR-4354:
---------------------------------------------
Amit, I don't complete understand the problem.
bq. Slave now tries to pull from master B (has higher index version than slave
but lower generation)
Say, slave has generation G and version V and master(B) has a higher version
V+1 but lower generation G-1. The code right now says:
{code}
boolean isFullCopyNeeded = IndexDeletionPolicyWrapper
.getCommitTimestamp(commit) >= latestVersion
- || commit.getGeneration() >= latestGeneration || forceReplication;
{code}
Since master's generation is lower than slave, a full copy will be forced here.
Further, your patch has:
{code}
- || commit.getGeneration() >= latestGeneration || forceReplication;
+ || commit.getGeneration() >= latestGeneration ||
(commit.getGeneration() > latestGeneration) || forceReplication;
{code}
I don't see how that changes anything. The second condition on generation is
redundant. Did I miss something?
> Replication should perform full copy if slave's generation higher than
> master's
> -------------------------------------------------------------------------------
>
> Key: SOLR-4354
> URL: https://issues.apache.org/jira/browse/SOLR-4354
> Project: Solr
> Issue Type: Bug
> Components: replication (java)
> Affects Versions: 4.1
> Reporter: Amit Nithian
> Fix For: 4.2
>
> Attachments: SOLR-4354.patch
>
> Original Estimate: 1h
> Remaining Estimate: 1h
>
> We have dual masters each incrementally indexing from our MySQL database and
> sit behind a virtual hostname in our load balancer. As such, it's possible
> that the generation numbers between the masters for a given index are not in
> sync. Slaves are configured to replicate from this virtual host (and pin
> based on source/dest IP hash) so we can add and remove masters as necessary
> (great for maintenance).
> For the most part this works but we've seen the following happen:
> * Slave has been pulling from master A
> * Master A goes down for maint and now will pull from master B (which has a
> lower generation number for some reason than master A).
> * Slave now tries to pull from master B (has higher index version than slave
> but lower generation).
> * Slave downloads index files, moves them to the index/ directory but these
> files are deleted during the doCommit() phase (looks like older generation
> data is deleted).
> * Index remains as-is and no change.
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