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https://issues.apache.org/jira/browse/SOLR-5944?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14943734#comment-14943734
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Yonik Seeley commented on SOLR-5944:
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bq. I need to do the due diligence and write some tests to verify that things
will work with log replays and peer sync.
Yeah, things are tricky enough in this area (distributed updates / recovery in
general) that one can't really validate through tests. Need to brainstorm and
think through all of the different failure scenarios and then try to use tests
to uncover scenarios you hadn't considered.
bq. This prevPointer is just used (in the patch) for RTGs. In the
InPlaceUpdateDistribTest, I've introduced commits (with 1/3 probability) in
between the re-ordered updates, and the RTG seems to work fine.
Ah, that makes sense now (for standalone / leader at least).
Off the top of my head, here's a possible issue:
- replica buffers a partial update in memory (because it was reordered)
- a commit comes in, and we roll over to a new tlog
- node goes down and then comes back up, and the in-memory update is no longer
in memory, and the old tlog won't be replayed. It will look like we applied
that update.
bq. Is it okay to return success if it was written to (at least) the in-memory
buffer (which holds these reordered updates)?
I don't think so... another scenario:
- a client does an in-place update
- the replicas receive the update reordered, and buffer in memory.
- the client gets the response
- the leader goes down (and stays down... hard drive crash)
- one of the other replicas takes over as leader, but we've now lost data we
confirmed as written (the in-place update was only ever applied on the leader),
even though we only lost 1 server.
And then there is the even simpler scenario I think you were alluding to: if an
update is ack'd, then a RTG on any active replica should see that update (or a
later one).
> Support updates of numeric DocValues
> ------------------------------------
>
> Key: SOLR-5944
> URL: https://issues.apache.org/jira/browse/SOLR-5944
> Project: Solr
> Issue Type: New Feature
> Reporter: Ishan Chattopadhyaya
> Assignee: Shalin Shekhar Mangar
> Attachments: SOLR-5944.patch, SOLR-5944.patch, SOLR-5944.patch,
> SOLR-5944.patch, SOLR-5944.patch, SOLR-5944.patch, SOLR-5944.patch,
> SOLR-5944.patch, SOLR-5944.patch, SOLR-5944.patch, SOLR-5944.patch,
> SOLR-5944.patch
>
>
> LUCENE-5189 introduced support for updates to numeric docvalues. It would be
> really nice to have Solr support this.
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