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

Author: anarazel

src/backend/replication/basebackup.c

@@ -471,6 +471,7 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 					errmsg("unexpected WAL file size \"%s\"", walFiles[i])));
 			}
 
+			/* send the WAL file itself */
 			_tarWriteHeader(pathbuf, NULL, &statbuf);
 
 			while ((cnt = fread(buf, 1, Min(sizeof(buf), XLogSegSize - len), fp)) > 0)
@@ -497,7 +498,17 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 			}
 
 			/* XLogSegSize is a multiple of 512, so no need for padding */
+
 			FreeFile(fp);
+
+			/*
+			 * Mark file as archived, otherwise files can get archived again
+			 * after promotion of a new node. This is in line with
+			 * walreceiver.c always doing a XLogArchiveForceDone() after a
+			 * complete segment.
+			 */
+			StatusFilePath(pathbuf, walFiles[i], ".done");
+			sendFileWithContent(pathbuf, "");
 		}
 
 		/*
@@ -521,6 +532,10 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 						 errmsg("could not stat file \"%s\": %m", pathbuf)));
 
 			sendFile(pathbuf, pathbuf, &statbuf, false);
+
+			/* unconditionally mark file as archived */
+			StatusFilePath(pathbuf, fname, ".done");
+			sendFileWithContent(pathbuf, "");
 		}
 
 		/* Send CopyDone message for the last tar file */
@@ -1021,6 +1036,15 @@ sendDir(char *path, int basepathlen, bool sizeonly, List *tablespaces)
 				_tarWriteHeader(pathbuf + basepathlen + 1, NULL, &statbuf);
 			}
 			size += 512;		/* Size of the header just added */
+
+			/*
+			 * Also send archive_status directory (by hackishly reusing
+			 * statbuf from above ...).
+			 */
+			if (!sizeonly)
+				_tarWriteHeader("./pg_xlog/archive_status", NULL, &statbuf);
+			size += 512;		/* Size of the header just added */
+
 			continue;			/* don't recurse into pg_xlog */
 		}
 

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"),

src/bin/pg_basebackup/pg_receivexlog.c

@@ -342,7 +342,7 @@ StreamLog(void)
 
 	ReceiveXlogStream(conn, startpos, starttli, NULL, basedir,
 					  stop_streaming, standby_message_timeout, ".partial",
-					  synchronous);
+					  synchronous, false);
 
 	PQfinish(conn);
 	conn = NULL;

src/bin/pg_basebackup/receivelog.c

@@ -37,28 +37,58 @@ static PGresult *HandleCopyStream(PGconn *conn, XLogRecPtr startpos,
 				 uint32 timeline, char *basedir,
 			   stream_stop_callback stream_stop, int standby_message_timeout,
 				  char *partial_suffix, XLogRecPtr *stoppos,
-				  bool synchronous);
+				  bool synchronous, bool mark_done);
 static int CopyStreamPoll(PGconn *conn, long timeout_ms);
 static int CopyStreamReceive(PGconn *conn, long timeout, char **buffer);
 static bool ProcessKeepaliveMsg(PGconn *conn, char *copybuf, int len,
 								XLogRecPtr blockpos, int64 *last_status);
 static bool ProcessXLogDataMsg(PGconn *conn, char *copybuf, int len,
 							   XLogRecPtr *blockpos, uint32 timeline,
 							   char *basedir, stream_stop_callback stream_stop,
-							   char *partial_suffix);
+							   char *partial_suffix, bool mark_done);
 static PGresult *HandleEndOfCopyStream(PGconn *conn, char *copybuf,
 									   XLogRecPtr blockpos, char *basedir, char *partial_suffix,
-									   XLogRecPtr *stoppos);
+									   XLogRecPtr *stoppos, bool mark_done);
 static bool CheckCopyStreamStop(PGconn *conn, XLogRecPtr blockpos,
 								uint32 timeline, char *basedir,
 								stream_stop_callback stream_stop,
-								char *partial_suffix, XLogRecPtr *stoppos);
+								char *partial_suffix, XLogRecPtr *stoppos,
+								bool mark_done);
 static long CalculateCopyStreamSleeptime(int64 now, int standby_message_timeout,
 										 int64 last_status);
 
 static bool ReadEndOfStreamingResult(PGresult *res, XLogRecPtr *startpos,
 						 uint32 *timeline);
 
+static bool
+mark_file_as_archived(const char *basedir, const char *fname)
+{
+	int fd;
+	static char tmppath[MAXPGPATH];
+
+	snprintf(tmppath, sizeof(tmppath), "%s/archive_status/%s.done",
+			 basedir, fname);
+
+	fd = open(tmppath, O_WRONLY | O_CREAT | PG_BINARY, S_IRUSR | S_IWUSR);
+	if (fd < 0)
+	{
+		fprintf(stderr, _("%s: could not create archive status file \"%s\": %s\n"),
+				progname, tmppath, strerror(errno));
+		return false;
+	}
+
+	if (fsync(fd) != 0)
+	{
+		fprintf(stderr, _("%s: could not fsync file \"%s\": %s\n"),
+				progname, tmppath, strerror(errno));
+		return false;
+	}
+
+	close(fd);
+
+	return true;
+}
+
 /*
  * Open a new WAL file in the specified directory.
  *
@@ -152,7 +182,7 @@ open_walfile(XLogRecPtr startpoint, uint32 timeline, char *basedir,
  * and returns false, otherwise returns true.
  */
 static bool
-close_walfile(char *basedir, char *partial_suffix, XLogRecPtr pos)
+close_walfile(char *basedir, char *partial_suffix, XLogRecPtr pos, bool mark_done)
 {
 	off_t		currpos;
 
@@ -206,6 +236,19 @@ close_walfile(char *basedir, char *partial_suffix, XLogRecPtr pos)
 				_("%s: not renaming \"%s%s\", segment is not complete\n"),
 				progname, current_walfile_name, partial_suffix);
 
+	/*
+	 * Mark file as archived if requested by the caller - pg_basebackup needs
+	 * to do so as files can otherwise get archived again after promotion of a
+	 * new node. This is in line with walreceiver.c always doing a
+	 * XLogArchiveForceDone() after a complete segment.
+	 */
+	if (currpos == XLOG_SEG_SIZE && mark_done)
+	{
+		/* writes error message if failed */
+		if (!mark_file_as_archived(basedir, current_walfile_name))
+			return false;
+	}
+
 	lastFlushPosition = pos;
 	return true;
 }
@@ -248,7 +291,8 @@ existsTimeLineHistoryFile(char *basedir, TimeLineID tli)
 }
 
 static bool
-writeTimeLineHistoryFile(char *basedir, TimeLineID tli, char *filename, char *content)
+writeTimeLineHistoryFile(char *basedir, TimeLineID tli, char *filename,
+						 char *content, bool mark_done)
 {
 	int			size = strlen(content);
 	char		path[MAXPGPATH];
@@ -327,6 +371,14 @@ writeTimeLineHistoryFile(char *basedir, TimeLineID tli, char *filename, char *co
 		return false;
 	}
 
+	/* Maintain archive_status, check close_walfile() for details. */
+	if (mark_done)
+	{
+		/* writes error message if failed */
+		if (!mark_file_as_archived(basedir, histfname))
+			return false;
+	}
+
 	return true;
 }
 
@@ -447,7 +499,7 @@ ReceiveXlogStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
 				  char *sysidentifier, char *basedir,
 				  stream_stop_callback stream_stop,
 				  int standby_message_timeout, char *partial_suffix,
-				  bool synchronous)
+				  bool synchronous, bool mark_done)
 {
 	char		query[128];
 	char		slotcmd[128];
@@ -562,7 +614,8 @@ ReceiveXlogStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
 			/* Write the history file to disk */
 			writeTimeLineHistoryFile(basedir, timeline,
 									 PQgetvalue(res, 0, 0),
-									 PQgetvalue(res, 0, 1));
+									 PQgetvalue(res, 0, 1),
+									 mark_done);
 
 			PQclear(res);
 		}
@@ -592,7 +645,7 @@ ReceiveXlogStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
 		/* Stream the WAL */
 		res = HandleCopyStream(conn, startpos, timeline, basedir, stream_stop,
 							   standby_message_timeout, partial_suffix,
-							   &stoppos, synchronous);
+							   &stoppos, synchronous, mark_done);
 		if (res == NULL)
 			goto error;
 
@@ -757,7 +810,7 @@ static PGresult *
 HandleCopyStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
 				 char *basedir, stream_stop_callback stream_stop,
 				 int standby_message_timeout, char *partial_suffix,
-				 XLogRecPtr *stoppos, bool synchronous)
+				 XLogRecPtr *stoppos, bool synchronous, bool mark_done)
 {
 	char	   *copybuf = NULL;
 	int64		last_status = -1;
@@ -775,7 +828,8 @@ HandleCopyStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
 		 * Check if we should continue streaming, or abort at this point.
 		 */
 		if (!CheckCopyStreamStop(conn, blockpos, timeline, basedir,
-								stream_stop, partial_suffix, stoppos))
+								stream_stop, partial_suffix, stoppos,
+								mark_done))
 			goto error;
 
 		now = feGetCurrentTimestamp();
@@ -830,7 +884,8 @@ HandleCopyStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
 			if (r == -2)
 			{
 				PGresult	*res = HandleEndOfCopyStream(conn, copybuf, blockpos,
-														 basedir, partial_suffix, stoppos);
+														 basedir, partial_suffix,
+														 stoppos, mark_done);
 				if (res == NULL)
 					goto error;
 				else
@@ -847,14 +902,16 @@ HandleCopyStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
 			else if (copybuf[0] == 'w')
 			{
 				if (!ProcessXLogDataMsg(conn, copybuf, r, &blockpos,
-										timeline, basedir, stream_stop, partial_suffix))
+										timeline, basedir, stream_stop,
+										partial_suffix, true))
 					goto error;
 
 				/*
 				 * Check if we should continue streaming, or abort at this point.
 				 */
 				if (!CheckCopyStreamStop(conn, blockpos, timeline, basedir,
-										 stream_stop, partial_suffix, stoppos))
+										 stream_stop, partial_suffix, stoppos,
+										 mark_done))
 					goto error;
 			}
 			else
@@ -1055,7 +1112,7 @@ static bool
 ProcessXLogDataMsg(PGconn *conn, char *copybuf, int len,
 				   XLogRecPtr *blockpos, uint32 timeline,
 				   char *basedir, stream_stop_callback stream_stop,
-				   char *partial_suffix)
+				   char *partial_suffix, bool mark_done)
 {
 	int			xlogoff;
 	int			bytes_left;
@@ -1163,7 +1220,7 @@ ProcessXLogDataMsg(PGconn *conn, char *copybuf, int len,
 		/* Did we reach the end of a WAL segment? */
 		if (*blockpos % XLOG_SEG_SIZE == 0)
 		{
-			if (!close_walfile(basedir, partial_suffix, *blockpos))
+			if (!close_walfile(basedir, partial_suffix, *blockpos, mark_done))
 				/* Error message written in close_walfile() */
 				return false;
 
@@ -1193,7 +1250,7 @@ ProcessXLogDataMsg(PGconn *conn, char *copybuf, int len,
 static PGresult *
 HandleEndOfCopyStream(PGconn *conn, char *copybuf,
 					  XLogRecPtr blockpos, char *basedir, char *partial_suffix,
-					  XLogRecPtr *stoppos)
+					  XLogRecPtr *stoppos, bool mark_done)
 {
 	PGresult   *res = PQgetResult(conn);
 
@@ -1204,7 +1261,7 @@ HandleEndOfCopyStream(PGconn *conn, char *copybuf,
 	 */
 	if (still_sending)
 	{
-		if (!close_walfile(basedir, partial_suffix, blockpos))
+		if (!close_walfile(basedir, partial_suffix, blockpos, mark_done))
 		{
 			/* Error message written in close_walfile() */
 			PQclear(res);
@@ -1236,11 +1293,11 @@ HandleEndOfCopyStream(PGconn *conn, char *copybuf,
 static bool
 CheckCopyStreamStop(PGconn *conn, XLogRecPtr blockpos, uint32 timeline,
 					char *basedir, stream_stop_callback stream_stop,
-					char *partial_suffix, XLogRecPtr *stoppos)
+					char *partial_suffix, XLogRecPtr *stoppos, bool mark_done)
 {
 	if (still_sending && stream_stop(blockpos, timeline, false))
 	{
-		if (!close_walfile(basedir, partial_suffix, blockpos))
+		if (!close_walfile(basedir, partial_suffix, blockpos, mark_done))
 		{
 			/* Potential error message is written by close_walfile */
 			return false;

src/bin/pg_basebackup/receivelog.h

@@ -31,6 +31,7 @@ extern bool ReceiveXlogStream(PGconn *conn,
 				  stream_stop_callback stream_stop,
 				  int standby_message_timeout,
 				  char *partial_suffix,
-				  bool synchronous);
+				  bool synchronous,
+				  bool mark_done);
 
 #endif	/* RECEIVELOG_H */