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From "Devaraj Das (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7213) Have HLog files for .META. edits only
Date Wed, 05 Dec 2012 22:07:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7213?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13510829#comment-13510829

Devaraj Das commented on HBASE-7213:

bq. Do other logs have a '.log' suffix? You add .hlog with the below?

Currently (in the trunk codebase), the log files don't have extension like .log or something
(the files look like They are in directory
called ".logs/<region-server>". So I am wondering whether I should just have ".meta"
as the suffix for the meta log files, and be done with it (as I had it in the previous patch).
In the current patch, the meta logs have .meta.hlog as the extension. Or, would it make sense
to change the log files to have ".hlog" extension as well? Please let me know..

bq. The SSH changes look good. There is a hole though at the moment around ROOT handling?
We need to wait on ROOT removal before this can go in, right? (The RootServerShutdownHandler
would go....or should RSSH be calling MSSH when it is done w/ its process?)

It can be done either way in theory (HBASE-3171 first or this first). On the hole, yes, if
this patch goes in first, and if there is a case where the same RS hosts both the root and
meta regions, and that RS goes down, and the root's edits weren't already persisted, there
will be a problem. But given that the root doesn't have edits other than the one row to do
with .META., it is unlikely that we will run into the hole in practice. But am okay to wait
till HBASE-3171 goes in (and that's a better way to line the commits, but would like to close
on on the other comments).

bq. This below is given to an executor? Should have a better name than handler?
bq. + private UncaughtExceptionHandler handler;

Will take a look and update.

bq. Will we always create the metahlog just because getMetaHLog was called? Even if we are
NOT carrying .META.:

No. It'll be created on the first call to getMetaWAL (and getMetaWAL gets indirectly called
only when we are asked to open the meta region in OpenRegionHandler)

bq. If .META. moves away from a RS and then comes back, we'll just use the already made meta
log roller, etc.?


bq. Replication will skip this .META. log?

Yes. The MetaLogRoller doesn't "register" with the Replication folks when instantiated.

bq. It is intentional that MetaServices is still in the patch?

Mistake.. Will update.

bq. In SplitLogManager, we have added splitMetaLogDistributed. A more generic method might
have been splitLogDistributed that took a file path filter instead...

Hmm.. Let me see..

bq. There is a define for .META. HRegionInfo in HRegionInfo#FIRST_META_REGIONINFO so you don't
have to make it each time, FYI.

I had seen this one but had forgotten to update code to use it.. will update.

bq. Don't have to deprecate the below I'd say. This is for 0.96 the singularity and this is
on a class with annotation @InterfaceAudience.Private
bq. /** @return the HLog */
bq. + @Deprecated
bq. public HLog getWAL();


return new Path(dir, prefix + "." + filenum);
+ String child = prefix + "." + filenum;
+ return new Path(dir, child);
the 'normal' WALs do not seem to pick up the suffix in here. Is it possible that the '.log'
is appended elsewhere? Are your .META. logs getting double '.log'? Just wondering.

No.. as I said before, the log files don't have the string extensions.. So what do you think
- should I just remove the .hlog from the .meta.hlog extension that I did for meta hlogs?
Or, leave .meta.hlog as it is and add .hlog to the non-meta hlog files, or, leave the non-meta
hlog names as they are now?
> Have HLog files for .META. edits only
> -------------------------------------
>                 Key: HBASE-7213
>                 URL: https://issues.apache.org/jira/browse/HBASE-7213
>             Project: HBase
>          Issue Type: Improvement
>          Components: master, regionserver
>            Reporter: Devaraj Das
>            Assignee: Devaraj Das
>             Fix For: 0.96.0
>         Attachments: 7213-2.4.patch, 7213-in-progress.2.2.patch, 7213-in-progress.2.patch,
> Over on HBASE-6774, there is a discussion on separating out the edits for .META. regions
from the other regions' edits w.r.t where the edits are written. This jira is to track an
implementation of that.

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