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https://issues.apache.org/jira/browse/HBASE-1364?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12849082#action_12849082
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stack commented on HBASE-1364:
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I was thinking that we could use a coprocessor to do log sort/split. One thing
that needs addressing is that each Store in a Region reads the whole log
itself. Seems like reading of the old edits should be done once at region
level (I don't think this would be hard to do). Other things, in BT paper,
they talk of regions asking for edits after they come back online. First, the
region is already online again before log split starts -- maybe its already
taking on writes? -- and second, somehow the region knew what logs they want
to get edits from (Recheck paper. I'm pulling from rusty memory).
> [performance] Distributed splitting of regionserver commit logs
> ---------------------------------------------------------------
>
> Key: HBASE-1364
> URL: https://issues.apache.org/jira/browse/HBASE-1364
> Project: Hadoop HBase
> Issue Type: Improvement
> Reporter: stack
> Priority: Critical
> Fix For: 0.21.0
>
>
> HBASE-1008 has some improvements to our log splitting on regionserver crash;
> but it needs to run even faster.
> (Below is from HBASE-1008)
> In bigtable paper, the split is distributed. If we're going to have 1000
> logs, we need to distribute or at least multithread the splitting.
> 1. As is, regions starting up expect to find one reconstruction log only.
> Need to make it so pick up a bunch of edit logs and it should be fine that
> logs are elsewhere in hdfs in an output directory written by all split
> participants whether multithreaded or a mapreduce-like distributed process
> (Lets write our distributed sort first as a MR so we learn whats involved;
> distributed sort, as much as possible should use MR framework pieces). On
> startup, regions go to this directory and pick up the files written by split
> participants deleting and clearing the dir when all have been read in. Making
> it so can take multiple logs for input, can also make the split process more
> robust rather than current tenuous process which loses all edits if it
> doesn't make it to the end without error.
> 2. Each column family rereads the reconstruction log to find its edits. Need
> to fix that. Split can sort the edits by column family so store only reads
> its edits.
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