I agree that a generic solution for all cluster xlators would be good.
Only question I have is whether parallel notifications are specially
handled somewhere.
For example, if client xlator sends EC_CHILD_DOWN after a timeout, it's
possible that an immediate EC_CHILD_UP is sent if the brick is
connected. In this case, the cluster xlator could receive both
notifications in any order (we have multi-threading), which is dangerous
if EC_CHILD_DOWN is processed after EC_CHILD_UP.
I've seen that protocol/client doesn't send one notification until the
previous one has been completed. However this assumes that there won't
be any xlator that delays the notification (i.e. sends it in background
at another moment). Is that a requirement to process notifications ?
otherwise the concurrent notifications problem could appear even if
protocol/client serializes them.
Xavi
On 07/02/2015 03:34 PM, Pranith Kumar Karampuri wrote:
hi,
When glusterfs mount process is coming up all cluster xlators wait
for at least one event from all the children before propagating the
status upwards. Sometimes client xlator takes upto 2 minutes to
propogate this
event(https://bugzilla.redhat.com/show_bug.cgi?id=1054694#c0) Due to
this xavi implemented timer in ec notify where we treat a child as down
if it doesn't come up in 10 seconds. Similar patch went up for review
@http://review.gluster.org/#/c/11113 for afr. Kritika raised an
interesting point in the review that all cluster xlators need to have
this logic for the mount to not hang, and the correct place to fix it
would be client xlator itself. i.e. add the timer logic in client
xlator. Which seems like a better approach. I just want to take inputs
from everyone before we go ahead in that direction.
i.e. on PARENT_UP in client xlator it will start a timer and if no rpc
notification is received in that timeout it treats the client xlator as
down.
Pranith
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