postgres

History

Tom Lane e5d494d78c Don't lose walreceiver start requests due to race condition in postmaster. When a walreceiver dies, the startup process will notice that and send a PMSIGNAL_START_WALRECEIVER signal to the postmaster, asking for a new walreceiver to be launched. There's a race condition, which at least in HEAD is very easy to hit, whereby the postmaster might see that signal before it processes the SIGCHLD from the walreceiver process. In that situation, sigusr1_handler() just dropped the start request on the floor, reasoning that it must be redundant. Eventually, after 10 seconds (WALRCV_STARTUP_TIMEOUT), the startup process would make a fresh request --- but that's a long time if the connection could have been re-established almost immediately. Fix it by setting a state flag inside the postmaster that we won't clear until we do launch a walreceiver. In cases where that results in an extra walreceiver launch, it's up to the walreceiver to realize it's unwanted and go away --- but we have, and need, that logic anyway for the opposite race case. I came across this through investigating unexpected delays in the src/test/recovery TAP tests: it manifests there in test cases where a master server is stopped and restarted while leaving streaming slaves active. This logic has been broken all along, so back-patch to all supported branches. Discussion: https://postgr.es/m/21344.1498494720@sss.pgh.pa.us		9 years ago
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Makefile	Allow background workers to be started dynamically.	13 years ago
autovacuum.c	Fix autovacuum launcher attachment to its DSA	9 years ago
bgworker.c	Phase 3 of pgindent updates.	9 years ago
bgwriter.c	Phase 2 of pgindent updates.	9 years ago
checkpointer.c	Phase 3 of pgindent updates.	9 years ago
fork_process.c	Phase 2 of pgindent updates.	9 years ago
pgarch.c	Phase 3 of pgindent updates.	9 years ago
pgstat.c	Ignore old stats file timestamps when starting the stats collector.	9 years ago
postmaster.c	Don't lose walreceiver start requests due to race condition in postmaster.	9 years ago
startup.c	Phase 2 of pgindent updates.	9 years ago
syslogger.c	Phase 3 of pgindent updates.	9 years ago
walwriter.c	Phase 2 of pgindent updates.	9 years ago