[Gluster-devel] Automated split-brain resolution

[Ravishankar N]

On 08/07/2014 03:06 PM, Niels de Vos wrote:
> On Thu, Aug 07, 2014 at 02:05:34PM +0530, Ravishankar N wrote:
>> Manual resolution of split-brains [1] has been a tedious task
>> involving understanding and modifying AFR's changelog extended
>> attributes. To simplify and to an extent automate this task, we are
>> proposing a new CLI command with which the user can  specify  what
>> the source brick/file is, and automatically heal the files in the
>> appropriate direction.
> What about automatically healing directories that are in split-brain?

Conservative merge happens when possible while healing directories, but 
yes gfid split-brain  (one brick having a file with gfid-g1 and the 
other having a directory with the same gfid-g1) won't be resolved with 
this command. The reason why are not wanting to it right now is 
resolving such split-brains involves unlinking/rmdir'ing one of the 
entries and is best when we integrate with trash xlator.
> Thanks,
> Niels
>
>> Command: gluster volume resolve-split-brain <VOLNAME> {<bigger_file>
>> |  source-brick <brick_name> [<file>] }
>>
>> Breaking up the command into its possible options, we have:
>>
>> a) gluster volume resolve-split-brain <VOLNAME> <bigger_file>
>> When this command is executed, AFR will consider the brick having
>> the highest file size as the source and heal it to all other bricks
>> (including all other sources and sinks) in that replica subvolume.
>> If the file size is same in all the bricks, it does *not* heal the
>> file.
>>
>> b) gluster volume resolve-split-brain <VOLNAME > source-brick
>> <brick_name > [<file>]
>>
>> When this command is executed, if <file> is specified, AFR heals the
>> file from the source-brick <brick_name> to all other bricks of that
>> replica subvolume. For resolving multiple files, the command must be
>> run iteratively, once per file.
>> If <file> is not specified, AFR heals all the files that have an
>> entry in .glusterfs/indices/xattrop *and* are in split-brain. As
>> before, heals happen from source-brick <brick_name> to all other
>> bricks.
>>
>> Future work could also include extending the command to add other
>> policies like choosing the file having the latest mtime as the
>> source, integration with trash xlator wherein the files deleted from
>> the sink are moved to the trash dir etc.
>>
>> Please give feedback on the above.
>>
>> Regards,
>> Ravi
>>
>> [1] https://github.com/gluster/glusterfs/blob/master/doc/split-brain.md
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