[Gluster-users] ... i was able to produce a split brain...

[Jeff Darcy]

> Pranith and I had a discussion regarding this issue and here is what we have
> in our mind right now.
> 
> We plan to provide the user commands to execute from mount so that he can
> access the files in split-brain. This way he can choose which copy is to be
> used as source. The user will have to perform a set of getfattrs and
> setfattrs (on virtual xattrs) to decide which child to choose as source and
> inform AFR with his decision.
> 
> A) To know the split-brain status :
> getfattr -n trusted.afr.split-brain-status <path-to-file>
> 
> This will provide user with the following details -
> 1) Whether the file is in metadata split-brain
> 2) Whether the file is in data split-brain
> 
> It will also list the name of afr-children to choose from. Something like :
> Option0: client-0
> Option1: client-1
> 
> We also tell the user what the user could do to view metadata/data info; like
> stat to get metadata etc.
> 
> B) Now the user has to choose one of the options (client-x/client-y..) to
> inspect the files.
> e.g., setfattr -n trusted.afr.split-brain-choice -v client-0 <path-to-file>
> We save the read-child info in inode-ctx in order to provide the user access
> to the file in split-brain from that child. Once the user inspects the file,
> he proceeds to do the same from the other child of replica pair and makes an
> informed decision.
> 
> C) Once the above steps are done, AFR is to be informed with the final choice
> for source. This is achieved by -
> (say the fresh copy is in client-0)
> e.g., setfattr -n trusted.afr.split-brain-heal-finalize -v client-0
> <path-to-file>
> This child will be chosen as source and split-brain resolution will be done.

+1

That looks quite nice, and AFAICT shouldn't be prohibitively hard to
implement.