Start background writer during archive recovery. Background writer now performs

its usual buffer cleaning duties during archive recovery, and it's responsible
for performing restartpoints.

This requires some changes in postmaster. When the startup process has done
all the initialization and is ready to start WAL redo, it signals the
postmaster to launch the background writer. The postmaster is signaled again
when the point in recovery is reached where we know that the database is in
consistent state. Postmaster isn't interested in that at the moment, but
that's the point where we could let other backends in to perform read-only
queries. The postmaster is signaled third time when the recovery has ended,
so that postmaster knows that it's safe to start accepting connections.

The startup process now traps SIGTERM, and performs a "clean" shutdown. If
you do a fast shutdown during recovery, a shutdown restartpoint is performed,
like a shutdown checkpoint, and postmaster kills the processes cleanly. You
still have to continue the recovery at next startup, though.

Currently, the background writer is only launched during archive recovery.
We could launch it during crash recovery as well, but it seems better to keep
that codepath as simple as possible, for the sake of robustness. And it
couldn't do any restartpoints during crash recovery anyway, so it wouldn't be
that useful.

log_restartpoints is gone. Use log_checkpoints instead. This is yet to be
documented.

This whole operation is a pre-requisite for Hot Standby, but has some value of
its own whether the hot standby patch makes 8.4 or not.

Simon Riggs, with lots of modifications by me.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 99b0509311a..ca1d2361544 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/xlog.h,v 1.90 2009/01/20 18:59:37 heikki Exp $
+ * $PostgreSQL: pgsql/src/include/access/xlog.h,v 1.91 2009/02/18 15:58:41 heikki Exp $
  */
 #ifndef XLOG_H
 #define XLOG_H
@@ -199,6 +199,8 @@ extern void RestoreBkpBlocks(XLogRecPtr lsn, XLogRecord *record, bool cleanup);
 extern void xlog_redo(XLogRecPtr lsn, XLogRecord *record);
 extern void xlog_desc(StringInfo buf, uint8 xl_info, char *rec);
 
+extern bool RecoveryInProgress(void);
+
 extern void UpdateControlFile(void);
 extern Size XLOGShmemSize(void);
 extern void XLOGShmemInit(void);
@@ -207,9 +209,12 @@ extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
 extern void InitXLOGAccess(void);
 extern void CreateCheckPoint(int flags);
+extern bool CreateRestartPoint(int flags);
 extern void XLogPutNextOid(Oid nextOid);
 extern XLogRecPtr GetRedoRecPtr(void);
 extern XLogRecPtr GetInsertRecPtr(void);
 extern void GetNextXidAndEpoch(TransactionId *xid, uint32 *epoch);
 
+extern void StartupProcessMain(void);
+
 #endif   /* XLOG_H */