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Tom Lane 0038f94387 Fix postmaster's behavior during smart shutdown. ... Up to now, upon receipt of a SIGTERM ("smart shutdown" command), the postmaster has immediately killed all "optional" background processes, and subsequently refused to launch new ones while it's waiting for foreground client processes to exit. No doubt this seemed like an OK policy at some point; but it's a pretty bad one now, because it makes for a seriously degraded environment for the remaining clients: * Parallel queries are killed, and new ones fail to launch. (And our parallel-query infrastructure utterly fails to deal with the case in a reasonable way --- it just hangs waiting for workers that are not going to arrive. There is more work needed in that area IMO.) * Autovacuum ceases to function. We can tolerate that for awhile, but if bulk-update queries continue to run in the surviving client sessions, there's eventually going to be a mess. In the worst case the system could reach a forced shutdown to prevent XID wraparound. * The bgwriter and walwriter are also stopped immediately, likely resulting in performance degradation. Hence, let's rearrange things so that the only immediate change in behavior is refusing to let in new normal connections. Once the last normal connection is gone, shut everything down as though we'd received a "fast" shutdown. To implement this, remove the PM_WAIT_BACKUP and PM_WAIT_READONLY states, instead staying in PM_RUN or PM_HOT_STANDBY while normal connections remain. A subsidiary state variable tracks whether or not we're letting in new connections in those states. This also allows having just one copy of the logic for killing child processes in smart and fast shutdown modes. I moved that logic into PostmasterStateMachine() by inventing a new state PM_STOP_BACKENDS. Back-patch to 9.6 where parallel query was added. In principle this'd be a good idea in 9.5 as well, but the risk/reward ratio is not as good there, since lack of autovacuum is not a problem during typical uses of smart shutdown. Per report from Bharath Rupireddy. Patch by me, reviewed by Thomas Munro Discussion: https://postgr.es/m/CALj2ACXAZ5vKxT9P7P89D87i3MDO9bfS+_bjMHgnWJs8uwUOOw@mail.gmail.com		5 years ago
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backend	Fix postmaster's behavior during smart shutdown.	5 years ago
bin	Rename VariableCacheData.nextFullXid to nextXid.	5 years ago
common	Replace remaining StrNCpy() by strlcpy()	5 years ago
fe_utils	Move connect.h from fe_utils to src/include/common.	5 years ago
include	Fix postmaster's behavior during smart shutdown.	5 years ago
interfaces	Replace remaining StrNCpy() by strlcpy()	5 years ago
makefiles	Remove libpq.rc, use win32ver.rc for libpq	6 years ago
pl	Fix -Wcast-function-type warnings	6 years ago
port	Remove optimization for RAND_poll() failing.	6 years ago
template	…
test	Fix typo in test comment.	5 years ago
timezone	Ensure that distributed timezone abbreviation files are plain ASCII.	6 years ago
tools	snapshot scalability: Don't compute global horizons while building snapshots.	5 years ago
tutorial	…
.gitignore	…
DEVELOPERS	…
Makefile	…
Makefile.global.in	Update Unicode data to Unicode 13.0.0 and CLDR 37	6 years ago
Makefile.shlib	Add PostgreSQL home page to --help output	6 years ago
nls-global.mk	…