[pgpool-committers: 4021] pgpool: Tightening up the watchdog cluster membership criteria.

[Muhammad Usama]

Tightening up the watchdog cluster membership criteria.

The watchdog node should only be considered as the part of the cluster either
if it is the Master node or if it is connected to that master node as a standby.
The nodes in the transient states (which are yet in the process of joining the
Mater node) or standby having the different master record should not be
considered the part of the watchdog cluster and should not be counted in the
quorum calculation.

Before this commit every node was considered as the part of the cluster as soon
as it becomes reachable to the master watchdog node, The problem with that
philosophy was, at the time of recovering from network partitioning/split-brain
situation both cluster leaders could have similar number of reachable
nodes and deciding the rightful master becomes difficult.

Branch
------
V3_6_STABLE

Details
-------
https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=ee0a415dc67df6dd478b0037416f059fdefbe36b

Modified Files
--------------
src/include/watchdog/watchdog.h     |   8 +-
src/include/watchdog/wd_json_data.h |   2 +-
src/tools/pcp/pcp_frontend_client.c |   2 +
src/watchdog/watchdog.c             | 493 ++++++++++++++++++++----------------
src/watchdog/wd_json_data.c         |  10 +-
5 files changed, 281 insertions(+), 234 deletions(-)