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From "Lars Hofhansl (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4608) HLog Compression
Date Wed, 14 Mar 2012 06:17:40 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4608?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13229010#comment-13229010
] 

Lars Hofhansl commented on HBASE-4608:
--------------------------------------

@Ted: The HLog compression we're doing here is less complicated and has (far) fewer implications
on other modules compared to HBASE-4218. I don't think that is a good comparison.

bq. LRUDictionary.class is passed to the context

You do have a point.
Maybe instead of saying
{code}
boolean compression = reader.isWALCompressionEnabled();
if (compression) {
...
{code}

it could be something like
{code}
HLogCompressionType type = reader.getCompressionType();
if (type == ...) {
...
{code}
(just made that up, but you get the idea, and should be an easy change)

@Stack: Is v27 up on RB? I looked at the earlier versions but haven't kept track recently.
I'll promise I'll do a review tomorrow. I find it a bit big to just look at the diff.
44% space saving is pretty awesome. I forget, do we also SNAPPY/LZO/GZ compress the HLogs?

                
> HLog Compression
> ----------------
>
>                 Key: HBASE-4608
>                 URL: https://issues.apache.org/jira/browse/HBASE-4608
>             Project: HBase
>          Issue Type: New Feature
>            Reporter: Li Pi
>            Assignee: stack
>             Fix For: 0.94.0
>
>         Attachments: 4608-v19.txt, 4608-v20.txt, 4608-v22.txt, 4608v1.txt, 4608v13.txt,
4608v13.txt, 4608v14.txt, 4608v15.txt, 4608v16.txt, 4608v17.txt, 4608v18.txt, 4608v23.txt,
4608v24.txt, 4608v25.txt, 4608v27.txt, 4608v5.txt, 4608v6.txt, 4608v7.txt, 4608v8fixed.txt
>
>
> The current bottleneck to HBase write speed is replicating the WAL appends across different
datanodes. We can speed up this process by compressing the HLog. Current plan involves using
a dictionary to compress table name, region id, cf name, and possibly other bits of repeated
data. Also, HLog format may be changed in other ways to produce a smaller HLog.

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