Function CheckArchiveTimeout

src/backend/postmaster/checkpointer.c:617–671

* CheckArchiveTimeout -- check for archive_timeout and switch xlog files * * This will switch to a new WAL file and force an archive file write if * meaningful activity is recorded in the current WAL file. This includes most * writes, including just a single checkpoint record, but excludes WAL records * that were inserted with the XLOG_MARK_UNIMPORTANT flag being set (like * snapshots of run

 * records.
 */
static void
CheckArchiveTimeout(void)
{
	pg_time_t	now;
	pg_time_t	last_time;
	XLogRecPtr	last_switch_lsn;

	if (XLogArchiveTimeout <= 0 || RecoveryInProgress())
		return;

	now = (pg_time_t) time(NULL);

	/* First we do a quick check using possibly-stale local state. */
	if ((int) (now - last_xlog_switch_time) < XLogArchiveTimeout)
		return;

	/*
	 * Update local state ... note that last_xlog_switch_time is the last time
	 * a switch was performed *or requested*.
	 */
	last_time = GetLastSegSwitchData(&last_switch_lsn);

	last_xlog_switch_time = Max(last_xlog_switch_time, last_time);

	/* Now we can do the real checks */
	if ((int) (now - last_xlog_switch_time) >= XLogArchiveTimeout)
	{
		/*
		 * Switch segment only when "important" WAL has been logged since the
		 * last segment switch (last_switch_lsn points to end of segment
		 * switch occurred in).
		 */
		if (GetLastImportantRecPtr() > last_switch_lsn)
		{
			XLogRecPtr	switchpoint;

			/* mark switch as unimportant, avoids triggering checkpoints */
			switchpoint = RequestXLogSwitch(true);

			/*
			 * If the returned pointer points exactly to a segment boundary,
			 * assume nothing happened.
			 */
			if (XLogSegmentOffset(switchpoint, wal_segment_size) != 0)
				elog(DEBUG1, "write-ahead log switch forced (archive_timeout=%d)",
					 XLogArchiveTimeout);
		}

		/*
		 * Update state in any case, so we don't retry constantly when the
		 * system is idle.
		 */
		last_xlog_switch_time = now;
	}
}

/*
 * Returns true if an immediate checkpoint request is pending.  (Note that