[pgpool-committers: 5679] pgpool: Avoid exit/fork storm of pool_worker_child process.

[Tatsuo Ishii]

Avoid exit/fork storm of pool_worker_child process.

pool_worker_child issues query to get WAL position using do_query(),
which could throws FATAL error. In this case pool_worker_child process
exits and Pgpool-II parent immediately forks new process. This cycle
indefinitely repeats and gives high load to the system.

This could easily happen. For example if ALWAYS_MASTER flag is
mistakenly set to standby node, it will cause an error:

ERROR:  recovery is in progress
HINT:  WAL control functions cannot be executed during recovery.
STATEMENT:  SELECT pg_current_wal_lsn()

To avoid the exit/fork storm, sleep sr_check_period.

Branch
------
V4_0_STABLE

Details
-------
https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=c670dbf2583d1941bbe949985335f37c68db4323

Modified Files
--------------
src/protocol/pool_process_query.c | 9 +++++++++
1 file changed, 9 insertions(+)