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From Chris Waterson <water...@maubi.net>
Subject Re: hbase corruption - missing region files in HDFS
Date Sun, 09 Dec 2012 23:29:41 GMT
Well, I upgraded to 0.92.2, since the version I was running on (0.92.1) didn't have those options
for "hbck".

That helped.

It took me a while to realize that I had to make the root filesystem writable so that "hbck

-repair" could create itself a directory.  So, once that was done, it at least ran through
to completion.

But the problem persisted in that there were blocks in META that didn't exist on the filesystem.
 One poor region server was assigned the sad task of attempting to open the non-existent directory,
which it slavishly reattempted again and again, filling its log with FileNotFoundException
stack traces.

For example,

2012-12-09 00:14:33,315 ERROR org.apache.hadoop.hbase.regionserver.handler.OpenRegionHandler:
Failed open of region=referrers,com.free-hdwallpapers.www/wallpapers/animals/mici/595718.jpg|com.free-hdwallpapers.www/wallpaper/animals/husky/270579,1354964606745.0c54fe59c58ddd6b34042ec98171bff7.
java.io.FileNotFoundException: File does not exist: /hbase/referrers/2cb553c74d52ddcbf31940f6c7128c63/main/33f1fd9efb944c4e982ba719cd7dde84
etc., etc.

In particular, the directory above "/hbase/referrers/2cb553...c63" simply did not exist at
all in HDFS. 

So I took matters into my own hands and created the missing "/hbase/referrers/2cb553...c63"
directory, its subdirectory "main", and attempted to create a zero-length file "331fd9...e84".
 This changed the firehose of exceptions from FileNotFoundException to CorruptHFileException.

So, I wrote a small program to emit a valid, empty HFile, and proceeded to place these files
at whatever places in HDFS that a FileNotFoundException was being thrown.  After creating
three or four of them, the exceptions stopped.

I then ran "hbck -repair" again, and upon completion it declared victory.

Again, I suspect that I got myself into this problem because I ran a machine out of disk space.
 It's likely that most folks are more clever than me, and so this problem hasn't arisen before.

On Dec 9, 2012, at 3:00 PM, "Kevin O'dell" <kevin.odell@cloudera.com> wrote:

> can you run hbase hbck -fixMeta -fixAssignments
> This should assign those region servers and fix the hole.
> On Sat, Dec 8, 2012 at 11:30 PM, Chris Waterson <waterson@maubi.net> wrote:
>> Hello!  I've gotten myself into trouble where I'm missing files on HDFS
>> that HBase thinks ought to be there.  In particular, running "hbase hbck"
>> yields the below message: two regions are "not deployed on any region
>> server" (because there is no file in HDFS for the region), and "there is a
>> hole in the region chain".
>> (FWIW, I suspect that this problem is due to a recent incident where we
>> ran the cluster out of disk space.)
>> I'm running 0.92.1, and have been staggering around trying to figure out
>> what procedure I ought to use to correct the problem, but my Google-fu is
>> too poor to have yielded results.  Any pointers would be appreciated!
>> thanks,
>> chris
>> ERROR: Region
>> referrers,com.free-hdwallpapers.www/wallpapers/animals/mici/595718.jpg|com.free-hdwallpapers.www/wallpaper/animals/husky/270579,1354964606745.0c54fe59c58ddd6b34042ec98171bff7.
>> not deployed on any region server.
>> ERROR: Region
>> referrers,com.free-hdwallpapers.www/wallpapers/anime/mici/78285.jpg|com.free-hdwallpapers.www/wallpaper/anime/wolf-furry/90641,1354964606745.d2451e8db0f2b9546cc42c6d260a2ab8.
>> not deployed on any region server.
>> ERROR: There is a hole in the region chain between
>> com.free-hdwallpapers.www/wallpapers/animals/mici/595718.jpg|com.free-hdwallpapers.www/wallpaper/animals/husky/270579
>> and
>> com.free-hdwallpapers.www/wallpapers/entertainment/mici/11840.jpg|com.free-hdwallpapers.www/wallpaper/entertainment/new-moon-bella-and-edward/12951.
>> You need to create a new regioninfo and region dir in hdfs to plug the
>> hole.
> -- 
> Kevin O'Dell
> Customer Operations Engineer, Cloudera

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