Prevent WAL files created by pg_basebackup -x/X from being archived again.
authorAndres Freund <andres@anarazel.de>
Sat, 3 Jan 2015 19:51:52 +0000 (20:51 +0100)
committerAndres Freund <andres@anarazel.de>
Sat, 3 Jan 2015 19:54:13 +0000 (20:54 +0100)
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

src/backend/replication/basebackup.c
src/bin/pg_basebackup/pg_basebackup.c
src/bin/pg_basebackup/pg_receivexlog.c
src/bin/pg_basebackup/receivelog.c
src/bin/pg_basebackup/receivelog.h

index c52e453d2fcca29d3ace418e3214bd0fb7f5d400..fcc7cf271b9ea1f778e3fc2420631f6b158419c7 100644 (file)
@@ -404,6 +404,7 @@ 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)
@@ -428,7 +429,17 @@ 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, "");
        }
 
        /*
@@ -452,6 +463,10 @@ 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 */
@@ -900,6 +915,15 @@ 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 */
        }
 
index b1bcf698eb66ea92e07cb3b016308b34a8a3e38e..e63bb7c53af6b036d6335e9bbc1bd33539248bd8 100644 (file)
@@ -28,6 +28,7 @@
 #include <zlib.h>
 #endif
 
+#include "common/string.h"
 #include "getopt_long.h"
 
 #include "receivelog.h"
@@ -266,7 +267,7 @@ LogStreamerMain(logstreamer_param *param)
    if (!ReceiveXlogStream(param->bgconn, param->startptr, param->timeline,
                           param->sysidentifier, param->xlogdir,
                           reached_end_position, standby_message_timeout,
-                          NULL))
+                          NULL, true))
 
        /*
         * Any errors will already have been reported in the function process,
@@ -290,6 +291,7 @@ 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;
@@ -324,13 +326,23 @@ 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
@@ -1003,10 +1015,12 @@ ReceiveAndUnpackTarFile(PGconn *conn, PGresult *res, int rownum)
                    {
                        /*
                         * When streaming WAL, pg_xlog will have been created
-                        * by the wal receiver process, so just ignore failure
-                        * on that.
+                        * by the wal receiver process. So just ignore creation
+                        * failures on related directories.
                         */
-                       if (!streamwal || 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"),
index 8d9f00e930fbdaf5af493d4016903079ebb02f0e..34d4612d9fcab77bf1fb52a8f11e6a38c5eeb466 100644 (file)
@@ -335,7 +335,8 @@ StreamLog(void)
                starttli);
 
    ReceiveXlogStream(conn, startpos, starttli, NULL, basedir,
-                     stop_streaming, standby_message_timeout, ".partial");
+                     stop_streaming, standby_message_timeout, ".partial",
+                     false);
 
    PQfinish(conn);
 }
index 33095304fa72a0deb1d5bb98b0073faacca1c352..b1e103e6348dd512bf486e56b62cd9cb2da521e3 100644 (file)
@@ -35,11 +35,41 @@ static char current_walfile_name[MAXPGPATH] = "";
 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);
+                char *partial_suffix, XLogRecPtr *stoppos,
+                bool mark_done);
 
 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.
  *
@@ -133,7 +163,7 @@ open_walfile(XLogRecPtr startpoint, uint32 timeline, char *basedir,
  * and returns false, otherwise returns true.
  */
 static bool
-close_walfile(char *basedir, char *partial_suffix)
+close_walfile(char *basedir, char *partial_suffix, bool mark_done)
 {
    off_t       currpos;
 
@@ -187,6 +217,19 @@ close_walfile(char *basedir, char *partial_suffix)
                _("%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;
+   }
+
    return true;
 }
 
@@ -285,7 +328,8 @@ 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];
@@ -364,6 +408,14 @@ 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;
 }
 
@@ -508,7 +560,8 @@ bool
 ReceiveXlogStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
                  char *sysidentifier, char *basedir,
                  stream_stop_callback stream_stop,
-                 int standby_message_timeout, char *partial_suffix)
+                 int standby_message_timeout, char *partial_suffix,
+                 bool mark_done)
 {
    char        query[128];
    PGresult   *res;
@@ -593,7 +646,8 @@ 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);
        }
@@ -622,7 +676,7 @@ ReceiveXlogStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
        /* Stream the WAL */
        res = HandleCopyStream(conn, startpos, timeline, basedir, stream_stop,
                               standby_message_timeout, partial_suffix,
-                              &stoppos);
+                              &stoppos, mark_done);
        if (res == NULL)
            goto error;
 
@@ -787,7 +841,7 @@ 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)
+                XLogRecPtr *stoppos, bool mark_done)
 {
    char       *copybuf = NULL;
    int64       last_status = -1;
@@ -814,7 +868,7 @@ HandleCopyStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
         */
        if (still_sending && stream_stop(blockpos, timeline, false))
        {
-           if (!close_walfile(basedir, partial_suffix))
+           if (!close_walfile(basedir, partial_suffix, mark_done))
            {
                /* Potential error message is written by close_walfile */
                goto error;
@@ -913,7 +967,7 @@ HandleCopyStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
             */
            if (still_sending)
            {
-               if (!close_walfile(basedir, partial_suffix))
+               if (!close_walfile(basedir, partial_suffix, mark_done))
                {
                    /* Error message written in close_walfile() */
                    PQclear(res);
@@ -1081,7 +1135,7 @@ HandleCopyStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
                /* Did we reach the end of a WAL segment? */
                if (blockpos % XLOG_SEG_SIZE == 0)
                {
-                   if (!close_walfile(basedir, partial_suffix))
+                   if (!close_walfile(basedir, partial_suffix, mark_done))
                        /* Error message written in close_walfile() */
                        goto error;
 
index 7c983cd604a42a78d8a75ca4843439e3fa9344e7..28c98c883be37f9810494346ee669327b16343bb 100644 (file)
@@ -14,4 +14,5 @@ extern bool ReceiveXlogStream(PGconn *conn,
                  char *basedir,
                  stream_stop_callback stream_stop,
                  int standby_message_timeout,
-                 char *partial_suffix);
+                 char *partial_suffix,
+                 bool mark_done);