Prevent WAL files created by pg_basebackup -x/X from being archived again.

WAL (and timeline history) files created by pg_basebackup did not
maintain the new base backup's archive status. That's currently not a
problem if the new node is used as a standby - but if that node is
promoted all still existing files can get archived again.  With a high
wal_keep_segment settings that can happen a significant time later -
which is quite confusing.

Change both the backend (for the -x/-X fetch case) and pg_basebackup
(for -X stream) itself to always mark WAL/timeline files included in
the base backup as .done. That's in line with walreceiver.c doing so.

The verbosity of the pg_basebackup changes show pretty clearly that it
needs some refactoring, but that'd result in not be backpatchable
changes.

Backpatch to 9.1 where pg_basebackup was introduced.

Discussion: 20141205002854.GE21964@awork2.anarazel.de

1 files changed, 23 insertions, 10 deletions

diff --git a/src/bin/pg_basebackup/pg_basebackup.c b/src/bin/pg_basebackup/pg_basebackup.c
index 0470401aea..ed2f3021d0 100644
--- a/src/bin/pg_basebackup/pg_basebackup.c
+++ b/src/bin/pg_basebackup/pg_basebackup.c
@@ -25,6 +25,7 @@
 #include <zlib.h>
 #endif
 
+#include "common/string.h"
 #include "getopt_long.h"
 #include "libpq-fe.h"
 #include "pqexpbuffer.h"
@@ -370,7 +371,7 @@ LogStreamerMain(logstreamer_param *param)
 	if (!ReceiveXlogStream(param->bgconn, param->startptr, param->timeline,
 						   param->sysidentifier, param->xlogdir,
 						   reached_end_position, standby_message_timeout,
-						   NULL, false))
+						   NULL, false, true))
 
 		/*
 		 * Any errors will already have been reported in the function process,
@@ -394,6 +395,7 @@ StartLogStreamer(char *startpos, uint32 timeline, char *sysidentifier)
 	logstreamer_param *param;
 	uint32		hi,
 				lo;
+	char		statusdir[MAXPGPATH];
 
 	param = pg_malloc0(sizeof(logstreamer_param));
 	param->timeline = timeline;
@@ -428,13 +430,23 @@ StartLogStreamer(char *startpos, uint32 timeline, char *sysidentifier)
 		/* Error message already written in GetConnection() */
 		exit(1);
 
+	snprintf(param->xlogdir, sizeof(param->xlogdir), "%s/pg_xlog", basedir);
+
 	/*
-	 * Always in plain format, so we can write to basedir/pg_xlog. But the
-	 * directory entry in the tar file may arrive later, so make sure it's
-	 * created before we start.
+	 * Create pg_xlog/archive_status (and thus pg_xlog) so we can can write to
+	 * basedir/pg_xlog as the directory entry in the tar file may arrive
+	 * later.
 	 */
-	snprintf(param->xlogdir, sizeof(param->xlogdir), "%s/pg_xlog", basedir);
-	verify_dir_is_empty_or_create(param->xlogdir);
+	snprintf(statusdir, sizeof(statusdir), "%s/pg_xlog/archive_status",
+			 basedir);
+
+	if (pg_mkdir_p(statusdir, S_IRWXU) != 0 && errno != EEXIST)
+	{
+		fprintf(stderr,
+				_("%s: could not create directory \"%s\": %s\n"),
+				progname, statusdir, strerror(errno));
+		disconnect_and_exit(1);
+	}
 
 	/*
 	 * Start a child process and tell it to start streaming. On Unix, this is
@@ -1236,11 +1248,12 @@ ReceiveAndUnpackTarFile(PGconn *conn, PGresult *res, int rownum)
 						 * by the wal receiver process. Also, when transaction
 						 * log directory location was specified, pg_xlog has
 						 * already been created as a symbolic link before
-						 * starting the actual backup. So just ignore failure
-						 * on them.
+						 * starting the actual backup. So just ignore creation
+						 * failures on related directories.
 						 */
-						if ((!streamwal && (strcmp(xlog_dir, "") == 0))
-							|| strcmp(filename + strlen(filename) - 8, "/pg_xlog") != 0)
+						if (!((pg_str_endswith(filename, "/pg_xlog") ||
+							   pg_str_endswith(filename, "/archive_status")) &&
+							  errno == EEXIST))
 						{
 							fprintf(stderr,
 							_("%s: could not create directory \"%s\": %s\n"),