[pgpool-committers: 4133] pgpool: Support AWS Aurora.

[Tatsuo Ishii]

Support AWS Aurora.

Add new backend flag "ALWAYS_MASTER" to control the primary node
detecting logic. Since we cannot use pg_is_in_recovery() in Aurora, we
assign the new flag to a backend which is specified as "writer" in
Aurora. Since Aurora always use the same hostname for the master (it's
called "writer"), find_primary_node() just returns the node id which
has ALWAYS_MASTER flag on.

Other than that, user can use the streaming replication mode with
Aurora. Notice that replication delay cannot be performed in Aurora,
sr_check_period should be always 0.

Branch
------
master

Details
-------
https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=e9b241e0d3ebde23433c4db59bcf6e31e9e730ef

Modified Files
--------------
src/config/pool_config.c                   | 176 ++++++++++++++++++-----------
src/config/pool_config.l                   |  11 ++
src/config/pool_config_variables.c         |  16 +++
src/include/pool_config.h                  |   3 +-
src/main/pgpool_main.c                     |  14 +++
src/sample/pgpool.conf.sample              |   3 +-
src/sample/pgpool.conf.sample-master-slave |   3 +-
src/sample/pgpool.conf.sample-stream       |   3 +-
src/tools/pgmd5/pool_config.c              | 176 ++++++++++++++++++-----------
9 files changed, 269 insertions(+), 136 deletions(-)