Problem:
--------
Each geo-rep workers process Changelogs available in their bricks,
if worker sees RMDIR, it tries to remove that directory recursively.
Since rmdir is recorded in all the bricks, rm -rf is executed
in parallel.
Due to DHTs open issues of parallel rm -rf, Some of the directories
will not get deleted in Slave Volume(Stale directory layout). If same
named dir is created in Master, then Geo-rep will end up in inconsistent
state since GFID is different for the new directory and directory
exists in Slave.
Solution - Fix in DHT:
---------------------
Hold lock during rmdir, so that parallel rmdir will get blocked and
no stale layouts.
Solution - Fix in Geo-rep:
--------------------------
Temporarily we can fix in Geo-rep till DHT fixes this issue. Since
Meta Volume is available with each Cluster, Geo-rep can keep lock
for GFID of dir to be deleted.
For example,
when rmdir:
while True:
try:
# fcntl lock in Meta volume $METAVOL/.rmdirlocks/<GFID>
get_lock(GFID)
recursive_delete()
release_and_del_lock_file()
break
except (EACCES, EAGAIN):
continue
One worker will succeed and all other workers will get ENOENT/ESTALE,
which can be safely ignored.
Let us know your thoughts.
--
regards
Aravinda
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