Cleanup and code review for the patch that made bgwriter active during

archive recovery.  Invent a separate state variable and inquiry function
for XLogInsertAllowed() to clarify some tests and make the management of
writing the end-of-recovery checkpoint less klugy.  Fix several places
that were incorrectly testing InRecovery when they should be looking at
RecoveryInProgress or XLogInsertAllowed (because they will now be executed
in the bgwriter not startup process).  Clarify handling of bad LSNs passed
to XLogFlush during recovery.  Use a spinlock for setting/testing
SharedRecoveryInProgress.  Improve quite a lot of comments.

Heikki and Tom

1 files changed, 17 insertions, 16 deletions

diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index c9b0e0ab2ec..3dbf36a6cf1 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -37,7 +37,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.582 2009/06/11 14:49:01 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.583 2009/06/26 20:29:04 tgl Exp $
  *
  * NOTES
  *
@@ -227,21 +227,22 @@ static bool RecoveryError = false;		/* T if WAL recovery failed */
  *
  * After doing all the postmaster initialization work, we enter PM_STARTUP
  * state and the startup process is launched. The startup process begins by
- * reading the control file and other preliminary initialization steps. When
- * it's ready to start WAL redo, it signals postmaster, and we switch to
- * PM_RECOVERY phase. The background writer is launched, while the startup
- * process continues applying WAL.
+ * reading the control file and other preliminary initialization steps.
+ * In a normal startup, or after crash recovery, the startup process exits
+ * with exit code 0 and we switch to PM_RUN state.  However, archive recovery
+ * is handled specially since it takes much longer and we would like to support
+ * hot standby during archive recovery.
  *
+ * When the startup process is ready to start archive recovery, it signals the
+ * postmaster, and we switch to PM_RECOVERY state. The background writer is
+ * launched, while the startup process continues applying WAL.
  * After reaching a consistent point in WAL redo, startup process signals
- * us again, and we switch to PM_RECOVERY_CONSISTENT phase. There's currently
+ * us again, and we switch to PM_RECOVERY_CONSISTENT state. There's currently
  * no difference between PM_RECOVERY and PM_RECOVERY_CONSISTENT, but we
  * could start accepting connections to perform read-only queries at this
  * point, if we had the infrastructure to do that.
- *
- * When WAL redo is finished, the startup process exits with exit code 0
- * and we switch to PM_RUN state. Startup process can also skip the
- * recovery and consistent recovery phases altogether, as it will during
- * normal startup when there's no recovery to be done, for example.
+ * When archive recovery is finished, the startup process exits with exit
+ * code 0 and we switch to PM_RUN state.
  *
  * Normal child backends can only be launched when we are in PM_RUN state.
  * (We also allow it in PM_WAIT_BACKUP state, but only for superusers.)
@@ -269,7 +270,7 @@ typedef enum
 {
 	PM_INIT,					/* postmaster starting */
 	PM_STARTUP,					/* waiting for startup subprocess */
-	PM_RECOVERY,				/* in recovery mode */
+	PM_RECOVERY,				/* in archive recovery mode */
 	PM_RECOVERY_CONSISTENT,		/* consistent recovery mode */
 	PM_RUN,						/* normal "database is alive" state */
 	PM_WAIT_BACKUP,				/* waiting for online backup mode to end */
@@ -2195,8 +2196,8 @@ reaper(SIGNAL_ARGS)
 
 			/*
 			 * Unexpected exit of startup process (including FATAL exit)
-			 * during PM_STARTUP is treated as catastrophic. There is no other
-			 * processes running yet, so we can just exit.
+			 * during PM_STARTUP is treated as catastrophic. There are no
+			 * other processes running yet, so we can just exit.
 			 */
 			if (pmState == PM_STARTUP && !EXIT_STATUS_0(exitstatus))
 			{
@@ -2247,7 +2248,7 @@ reaper(SIGNAL_ARGS)
 
 			/*
 			 * Crank up the background writer, if we didn't do that already
-			 * when we entered consistent recovery phase.  It doesn't matter
+			 * when we entered consistent recovery state.  It doesn't matter
 			 * if this fails, we'll just try again later.
 			 */
 			if (BgWriterPID == 0)
@@ -4008,7 +4009,7 @@ sigusr1_handler(SIGNAL_ARGS)
 		/*
 		 * Load the flat authorization file into postmaster's cache. The
 		 * startup process won't have recomputed this from the database yet,
-		 * so we it may change following recovery.
+		 * so it may change following recovery.
 		 */
 		load_role();