[
https://issues.apache.org/jira/browse/HBASE-17471?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15833836#comment-15833836
]
Yu Li commented on HBASE-17471:
-------------------------------
Ok, so you've already take the new design, quick action (smile).
I proposed to do this one and HBASE-17509 in parallel basically because the new
design need more testing to prove no performance regression. But since you've
already chosen to take the new design directly, let's go down this way. An
early reminder that we will need to supply performance number before commit.
Regarding the patch itself, it still looks in a draft style and could not apply
to master branch, but the main logic looks good and follows the new design.
Please rebase it on the latest code base and let's see how the UT works before
further review. Please also remove those commented out lines and upload a patch
on review board for easier review.
Let me close HBASE-17509 and focus here, but I'd suggest to change the title to
something similar to HBASE-17509 if we finally take the new design, not in a
hurry though.
> Region Seqid will be out of order in WAL if using mvccPreAssign
> ---------------------------------------------------------------
>
> Key: HBASE-17471
> URL: https://issues.apache.org/jira/browse/HBASE-17471
> Project: HBase
> Issue Type: Bug
> Components: wal
> Affects Versions: 2.0.0, 1.4.0
> Reporter: Allan Yang
> Assignee: Allan Yang
> Priority: Critical
> Attachments: HBASE-17471.patch, HBASE-17471.tmp, HBASE-17471.v2.patch
>
>
> mvccPreAssign was brought by HBASE-16698, which truly improved the
> performance of writing, especially in ASYNC_WAL scenario. But mvccPreAssign
> was only used in {{doMiniBatchMutate}}, not in Increment/Append path. If
> Increment/Append and batch put are using against the same region in parallel,
> then seqid of the same region may not monotonically increasing in the WAL.
> Since one write path acquires mvcc/seqid before append, and the other
> acquires in the append/sync consume thread.
> The out of order situation can easily reproduced by a simple UT, which was
> attached in the attachment. I modified the code to assert on the disorder:
> {code}
> if(this.highestSequenceIds.containsKey(encodedRegionName)) {
> assert highestSequenceIds.get(encodedRegionName) < sequenceid;
> }
> {code}
> I'd like to say, If we allow disorder in WALs, then this is not a issue.
> But as far as I know, if {{highestSequenceIds}} is not properly set, some
> WALs may not archive to oldWALs correctly.
> which I haven't figure out yet is that, will disorder in WAL cause data loss
> when recovering from disaster? If so, then it is a big problem need to be
> fixed.
> I have fix this problem in our costom1.1.x branch, my solution is using
> mvccPreAssign everywhere, making it un-configurable. Since mvccPreAssign it
> is indeed a better way than assign seqid in the ringbuffer thread while
> keeping handlers waiting for it.
> If anyone think it is doable, then I will port it to branch-1 and master
> branch and upload it.
>
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
