glusterd: reduce friend update flood

When in a befriended state, glusterd would broadcast friend updates to
all other peers whenver a ACC or LOCAL_ACC event occurred.

When a downed glusterd came back up and established connections again,
this lead to a flood of friend updates to happen on the order of N^2 (N
is the number of peers in the cluster)

In larger clusters this was problematic, and could lead to very long
times for the cluster to settle down when a peer came back up. Multiple
peers coming back up at the same time would compound the problem.

Broadcasting of friend updates doesn't have much use in places other
that during a peer probe. Instead of broadcasting friend updates on
connection re-establishment, updates can just be exchanged between the
peers involved in the connection.

This patch changes the glusterd friend state-machine to send updates
only to the required peer for ACC or LOCAL_ACC events when in befriended
state. The number of updates sent now is in the order of N.

For a 10 node cluster, the number of updates reduced by 5 times. When
creating the 10 node cluster, the updates reduced from ~500 to ~150.
When a glusterd restarted, the number of exchanges reduced from ~160 to
~35.

BUG: 1292749
Change-Id: Ib6072090c7069b081d018cdaa3dc878819ab1d18
Signed-off-by: Kaushal M <kaushal@redhat.com>
Reviewed-on: http://review.gluster.org/12999
Reviewed-by: Atin Mukherjee <amukherj@redhat.com>
Tested-by: NetBSD Build System <jenkins@build.gluster.org>
Tested-by: Gluster Build System <jenkins@build.gluster.com>

0 files changed, 0 insertions, 0 deletions