[Gluster-devel] Automated split-brain resolution

[Niels de Vos]

On Thu, Aug 07, 2014 at 03:17:11PM +0530, Ravishankar N wrote:
> 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.

Okay, good to know. Thanks!
Niels

> >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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>