Adjust error checks in pg_start_backup and pg_stop_backup to make it possible

to perform a backup without archive_mode being enabled.  This gives up some
user-error protection in order to improve usefulness for streaming-replication
scenarios.  Per discussion.

diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml
index 9055517af543114ac8e780dbc58a24152651ac18..f67b778a547f97421893b38d77c36683309d20e1 100644 (file)
--- a/doc/src/sgml/backup.sgml
+++ b/doc/src/sgml/backup.sgml
@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/backup.sgml,v 2.153 2010/04/28 16:10:39 heikki Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/backup.sgml,v 2.154 2010/04/29 21:49:03 tgl Exp $ -->
 
 <chapter id="backup">
  <title>Backup and Restore</title>
@@ -779,6 +779,7 @@ SELECT pg_stop_backup();
      Once the WAL segment files active during the backup are archived, you are
      done.  The file identified by <function>pg_stop_backup</>'s result is
      the last segment that is required to form a complete set of backup files.
+     If <varname>archive_mode</> is enabled,
      <function>pg_stop_backup</> does not return until the last segment has
      been archived.
      Archiving of these files happens automatically since you have

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 95c3c3a7d0a3ec8349847e330a4cd08c46fe8da5..61dfb20117f24d378ed2347ac445761e378135ca 100644 (file)
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.406 2010/04/29 21:36:19 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.407 2010/04/29 21:49:03 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -8205,18 +8205,11 @@ pg_start_backup(PG_FUNCTION_ARGS)
                 errmsg("recovery is in progress"),
                 errhint("WAL control functions cannot be executed during recovery.")));
 
-   if (!XLogArchivingActive())
-       ereport(ERROR,
-               (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
-                errmsg("WAL archiving is not active"),
-                errhint("archive_mode must be enabled at server start.")));
-
-   if (!XLogArchiveCommandSet())
+   if (!XLogIsNeeded())
        ereport(ERROR,
                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
-                errmsg("WAL archiving is not active"),
-                errhint("archive_command must be defined before "
-                        "online backups can be made safely.")));
+                errmsg("WAL level not sufficient for making an online backup"),
+                errhint("wal_level must be set to \"archive\" or \"hot_standby\" at server start.")));
 
    backupidstr = text_to_cstring(backupid);
 
@@ -8404,11 +8397,11 @@ pg_stop_backup(PG_FUNCTION_ARGS)
                 errmsg("recovery is in progress"),
                 errhint("WAL control functions cannot be executed during recovery.")));
 
-   if (!XLogArchivingActive())
+   if (!XLogIsNeeded())
        ereport(ERROR,
                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
-                errmsg("WAL archiving is not active"),
-                errhint("archive_mode must be enabled at server start.")));
+                errmsg("WAL level not sufficient for making an online backup"),
+                errhint("wal_level must be set to \"archive\" or \"hot_standby\" at server start.")));
 
    /*
     * OK to clear forcePageWrites
@@ -8516,16 +8509,26 @@ pg_stop_backup(PG_FUNCTION_ARGS)
    CleanupBackupHistory();
 
    /*
-    * Wait until both the last WAL file filled during backup and the history
-    * file have been archived.  We assume that the alphabetic sorting
-    * property of the WAL files ensures any earlier WAL files are safely
-    * archived as well.
+    * If archiving is enabled, wait for all the required WAL files to be
+    * archived before returning. If archiving isn't enabled, the required
+    * WAL needs to be transported via streaming replication (hopefully
+    * with wal_keep_segments set high enough), or some more exotic
+    * mechanism like polling and copying files from pg_xlog with script.
+    * We have no knowledge of those mechanisms, so it's up to the user to
+    * ensure that he gets all the required WAL.
+    *
+    * We wait until both the last WAL file filled during backup and the
+    * history file have been archived, and assume that the alphabetic
+    * sorting property of the WAL files ensures any earlier WAL files are
+    * safely archived as well.
     *
     * We wait forever, since archive_command is supposed to work and we
     * assume the admin wanted his backup to work completely. If you don't
     * wish to wait, you can set statement_timeout.  Also, some notices are
     * issued to clue in anyone who might be doing this interactively.
     */
+   if (XLogArchivingActive())
+   {
    XLByteToPrevSeg(stoppoint, _logId, _logSeg);
    XLogFileName(lastxlogfilename, ThisTimeLineID, _logId, _logSeg);
 
@@ -8564,6 +8567,10 @@ pg_stop_backup(PG_FUNCTION_ARGS)
 
    ereport(NOTICE,
            (errmsg("pg_stop_backup complete, all required WAL segments have been archived")));
+   }
+   else
+       ereport(NOTICE,
+               (errmsg("WAL archiving is not enabled; you must ensure that all required WAL segments are copied through other means to complete the backup")));
 
    /*
     * We're done.  As a convenience, return the ending WAL location.