Function PgstatCollectorMain

src/backend/postmaster/pgstat.c:3496–3782

---------- * PgstatCollectorMain() - * * Start up the statistics collector process. This is the body of the * postmaster child process. * * The argc/argv parameters are valid only in EXEC_BACKEND case. * ---------- */

 * ----------
 */
NON_EXEC_STATIC void
PgstatCollectorMain(int argc, char *argv[])
{
	int			len;
	PgStat_Msg	msg;
	int			wr;
	WaitEvent	event;
	WaitEventSet *wes;

	/*
	 * Ignore all signals usually bound to some action in the postmaster,
	 * except SIGHUP and SIGQUIT.  Note we don't need a SIGUSR1 handler to
	 * support latch operations, because we only use a local latch.
	 */
	pqsignal(SIGHUP, SignalHandlerForConfigReload);
	pqsignal(SIGINT, SIG_IGN);
	pqsignal(SIGTERM, SIG_IGN);
	pqsignal(SIGQUIT, SignalHandlerForShutdownRequest);
	pqsignal(SIGALRM, SIG_IGN);
	pqsignal(SIGPIPE, SIG_IGN);
	pqsignal(SIGUSR1, SIG_IGN);
	pqsignal(SIGUSR2, SIG_IGN);
	/* Reset some signals that are accepted by postmaster but not here */
	pqsignal(SIGCHLD, SIG_DFL);
	PG_SETMASK(&UnBlockSig);

	MyBackendType = B_STATS_COLLECTOR;
	init_ps_display(NULL);

	/*
	 * Read in existing stats files or initialize the stats to zero.
	 */
	pgStatRunningInCollector = true;
	pgStatDBHash = pgstat_read_statsfiles(InvalidOid, true, true);

	/* Prepare to wait for our latch or data in our socket. */
	wes = CreateWaitEventSet(CurrentMemoryContext, 3);
	AddWaitEventToSet(wes, WL_LATCH_SET, PGINVALID_SOCKET, MyLatch, NULL);
	AddWaitEventToSet(wes, WL_POSTMASTER_DEATH, PGINVALID_SOCKET, NULL, NULL);
	AddWaitEventToSet(wes, WL_SOCKET_READABLE, pgStatSock, NULL, NULL);

	/*
	 * Loop to process messages until we get SIGQUIT or detect ungraceful
	 * death of our parent postmaster.
	 *
	 * For performance reasons, we don't want to do ResetLatch/WaitLatch after
	 * every message; instead, do that only after a recv() fails to obtain a
	 * message.  (This effectively means that if backends are sending us stuff
	 * like mad, we won't notice postmaster death until things slack off a
	 * bit; which seems fine.)	To do that, we have an inner loop that
	 * iterates as long as recv() succeeds.  We do check ConfigReloadPending
	 * inside the inner loop, which means that such interrupts will get
	 * serviced but the latch won't get cleared until next time there is a
	 * break in the action.
	 */
	for (;;)
	{
		/* Clear any already-pending wakeups */