Remove exclusive backup mode

Exclusive-mode backups have been deprecated since 9.6 (when
non-exclusive backups were introduced) due to the issues
they can cause should the system crash while one is running and
generally because non-exclusive provides a much better interface.
Further, exclusive backup mode wasn't really being tested (nor was most
of the related code- like being able to log in just to stop an exclusive
backup and the bits of the state machine related to that) and having to
possibly deal with an exclusive backup and the backup_label file
existing during pg_basebackup, pg_rewind, etc, added other complexities
that we are better off without.

This patch removes the exclusive backup mode, the various special cases
for dealing with it, and greatly simplifies the online backup code and
documentation.

Authors: David Steele, Nathan Bossart
Reviewed-by: Chapman Flack
Discussion: https://postgr.es/m/ac7339ca-3718-3c93-929f-99e725d1172c@pgmasters.net
https://postgr.es/m/CAHg+QDfiM+WU61tF6=nPZocMZvHDzCK47Kneyb0ZRULYzV5sKQ@mail.gmail.com

1 files changed, 9 insertions, 11 deletions

diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index 6884cad2c00..815681ada7d 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -184,10 +184,8 @@ static const struct exclude_list_item excludeFiles[] =
 	{RELCACHE_INIT_FILENAME, true},
 
 	/*
-	 * If there's a backup_label or tablespace_map file, it belongs to a
-	 * backup started by the user with pg_start_backup().  It is *not* correct
-	 * for this backup.  Our backup_label/tablespace_map is injected into the
-	 * tar separately.
+	 * backup_label and tablespace_map should not exist in in a running cluster
+	 * capable of doing an online backup, but exclude them just in case.
 	 */
 	{BACKUP_LABEL_FILE, false},
 	{TABLESPACE_MAP, false},
@@ -264,16 +262,16 @@ perform_base_backup(basebackup_options *opt, bbsink *sink)
 	total_checksum_failures = 0;
 
 	basebackup_progress_wait_checkpoint();
-	state.startptr = do_pg_start_backup(opt->label, opt->fastcheckpoint,
+	state.startptr = do_pg_backup_start(opt->label, opt->fastcheckpoint,
 										&state.starttli,
 										labelfile, &state.tablespaces,
 										tblspc_map_file);
 
 	/*
-	 * Once do_pg_start_backup has been called, ensure that any failure causes
+	 * Once do_pg_backup_start has been called, ensure that any failure causes
 	 * us to abort the backup so we don't "leak" a backup counter. For this
-	 * reason, *all* functionality between do_pg_start_backup() and the end of
-	 * do_pg_stop_backup() should be inside the error cleanup block!
+	 * reason, *all* functionality between do_pg_backup_start() and the end of
+	 * do_pg_backup_stop() should be inside the error cleanup block!
 	 */
 
 	PG_ENSURE_ERROR_CLEANUP(do_pg_abort_backup, BoolGetDatum(false));
@@ -394,7 +392,7 @@ perform_base_backup(basebackup_options *opt, bbsink *sink)
 		}
 
 		basebackup_progress_wait_wal_archive(&state);
-		endptr = do_pg_stop_backup(labelfile->data, !opt->nowait, &endtli);
+		endptr = do_pg_backup_stop(labelfile->data, !opt->nowait, &endtli);
 	}
 	PG_END_ENSURE_ERROR_CLEANUP(do_pg_abort_backup, BoolGetDatum(false));
 
@@ -961,7 +959,7 @@ parse_basebackup_options(List *options, basebackup_options *opt)
 /*
  * SendBaseBackup() - send a complete base backup.
  *
- * The function will put the system into backup mode like pg_start_backup()
+ * The function will put the system into backup mode like pg_backup_start()
  * does, so that the backup is consistent even though we read directly from
  * the filesystem, bypassing the buffer cache.
  */
@@ -1204,7 +1202,7 @@ sendDir(bbsink *sink, const char *path, int basepathlen, bool sizeonly,
 		 * error in that case. The error handler further up will call
 		 * do_pg_abort_backup() for us. Also check that if the backup was
 		 * started while still in recovery, the server wasn't promoted.
-		 * do_pg_stop_backup() will check that too, but it's better to stop
+		 * do_pg_backup_stop() will check that too, but it's better to stop
 		 * the backup early than continue to the end and fail there.
 		 */
 		CHECK_FOR_INTERRUPTS();