Add a check on file size as an additional safety check that a WAL file

recovered from archive is not corrupt.  It's not much but it will catch
one common problem, viz out-of-disk-space.
Also, force a WAL recovery scan when recovery.conf is present, even if
pg_control shows a clean shutdown.  This allows recovery with a tar backup
that was taken with the postmaster shut down, as per complaint from
Mark Kirkwood.

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 40c11fb6bd071decf6594a86b054762d59640811..54a71b8f79d6ee3b666af47385173cf8fdc3cb4f 100644 (file)
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.150 2004/07/21 22:31:20 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.151 2004/07/22 20:18:40 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -432,7 +432,7 @@ static bool InstallXLogFileSegment(uint32 log, uint32 seg, char *tmppath,
 static int XLogFileOpen(uint32 log, uint32 seg);
 static int XLogFileRead(uint32 log, uint32 seg, int emode);
 static bool RestoreArchivedFile(char *path, const char *xlogfname,
-                               const char *recovername);
+                               const char *recovername, off_t expectedSize);
 static void PreallocXlogFiles(XLogRecPtr endptr);
 static void MoveOfflineLogs(uint32 log, uint32 seg, XLogRecPtr endptr);
 static XLogRecord *ReadRecord(XLogRecPtr *RecPtr, int emode, char *buffer);
@@ -1838,7 +1838,8 @@ XLogFileRead(uint32 log, uint32 seg, int emode)
        {
            XLogFileName(xlogfname, tli, log, seg);
            restoredFromArchive = RestoreArchivedFile(path, xlogfname,
-                                                     "RECOVERYXLOG");
+                                                     "RECOVERYXLOG",
+                                                     XLogSegSize);
        }
        else
            XLogFilePath(path, tli, log, seg);
@@ -1876,10 +1877,14 @@ XLogFileRead(uint32 log, uint32 seg, int emode)
  * If not successful, fill "path" with the name of the normal on-line file
  * (which may or may not actually exist, but we'll try to use it), and return
  * FALSE.
+ *
+ * For fixed-size files, the caller may pass the expected size as an
+ * additional crosscheck on successful recovery.  If the file size is not
+ * known, set expectedSize = 0.
  */
 static bool
 RestoreArchivedFile(char *path, const char *xlogfname,
-                   const char *recovername)
+                   const char *recovername, off_t expectedSize)
 {
    char xlogpath[MAXPGPATH];
    char xlogRestoreCmd[MAXPGPATH];
@@ -1991,19 +1996,42 @@ RestoreArchivedFile(char *path, const char *xlogfname,
    rc = system(xlogRestoreCmd);
    if (rc == 0)
    {
-       /* restore success ... assuming file is really there now ... */
-       if (stat(xlogpath, &stat_buf) == 0) {
-           ereport(LOG,
-                   (errmsg("restored log file \"%s\" from archive",
-                           xlogfname)));
-           strcpy(path, xlogpath);
-           return true;
+       /*
+        * command apparently succeeded, but let's make sure the file is
+        * really there now and has the correct size.
+        *
+        * XXX I made wrong-size a fatal error to ensure the DBA would
+        * notice it, but is that too strong?  We could try to plow ahead
+        * with a local copy of the file ... but the problem is that there
+        * probably isn't one, and we'd incorrectly conclude we've reached
+        * the end of WAL and we're done recovering ...
+        */
+       if (stat(xlogpath, &stat_buf) == 0)
+       {
+           if (expectedSize > 0 && stat_buf.st_size != expectedSize)
+               ereport(FATAL,
+                       (errmsg("archive file \"%s\" has wrong size: %lu instead of %lu",
+                               xlogfname,
+                               (unsigned long) stat_buf.st_size,
+                               (unsigned long) expectedSize)));
+           else
+           {
+               ereport(LOG,
+                       (errmsg("restored log file \"%s\" from archive",
+                               xlogfname)));
+               strcpy(path, xlogpath);
+               return true;
+           }
+       }
+       else
+       {
+           /* stat failed */
+           if (errno != ENOENT)
+               ereport(FATAL,
+                       (errcode_for_file_access(),
+                        errmsg("could not stat \"%s\": %m",
+                               xlogpath)));
        }
-       if (errno != ENOENT)
-           ereport(FATAL,
-                   (errcode_for_file_access(),
-                    errmsg("could not stat \"%s\": %m",
-                           xlogpath)));
    }
 
    /*
@@ -2664,7 +2692,7 @@ readTimeLineHistory(TimeLineID targetTLI)
    if (InArchiveRecovery)
    {
        TLHistoryFileName(histfname, targetTLI);
-       RestoreArchivedFile(path, histfname, "RECOVERYHISTORY");
+       RestoreArchivedFile(path, histfname, "RECOVERYHISTORY", 0);
    }
    else
        TLHistoryFilePath(path, targetTLI);
@@ -2749,7 +2777,7 @@ existsTimeLineHistory(TimeLineID probeTLI)
    if (InArchiveRecovery)
    {
        TLHistoryFileName(histfname, probeTLI);
-       RestoreArchivedFile(path, histfname, "RECOVERYHISTORY");
+       RestoreArchivedFile(path, histfname, "RECOVERYHISTORY", 0);
    }
    else
        TLHistoryFilePath(path, probeTLI);
@@ -2853,7 +2881,7 @@ writeTimeLineHistory(TimeLineID newTLI, TimeLineID parentTLI,
    if (InArchiveRecovery)
    {
        TLHistoryFileName(histfname, parentTLI);
-       RestoreArchivedFile(path, histfname, "RECOVERYHISTORY");
+       RestoreArchivedFile(path, histfname, "RECOVERYHISTORY", 0);
    }
    else
        TLHistoryFilePath(path, parentTLI);
@@ -4042,6 +4070,11 @@ StartupXLOG(void)
    if (checkPoint.undo.xrecoff == 0)
        checkPoint.undo = RecPtr;
 
+   /*
+    * Check whether we need to force recovery from WAL.  If it appears
+    * to have been a clean shutdown and we did not have a recovery.conf
+    * file, then assume no recovery needed.
+    */
    if (XLByteLT(checkPoint.undo, RecPtr) ||
        XLByteLT(checkPoint.redo, RecPtr))
    {
@@ -4054,13 +4087,23 @@ StartupXLOG(void)
        InRecovery = true;
 
    /* REDO */
-   if (InRecovery)
+   if (InRecovery || InArchiveRecovery)
    {
        int         rmid;
 
-       ereport(LOG,
-               (errmsg("database system was not properly shut down; "
-                       "automatic recovery in progress")));
+       if (InRecovery)
+       {
+           ereport(LOG,
+                   (errmsg("database system was not properly shut down; "
+                           "automatic recovery in progress")));
+       }
+       else
+       {
+           /* force recovery due to presence of recovery.conf */
+           InRecovery = true;
+           ereport(LOG,
+                   (errmsg("automatic recovery in progress")));
+       }
        ControlFile->state = DB_IN_RECOVERY;
        ControlFile->time = time(NULL);
        UpdateControlFile();
@@ -4158,8 +4201,11 @@ StartupXLOG(void)
            InRedo = false;
        }
        else
+       {
+           /* there are no WAL records following the checkpoint */
            ereport(LOG,
                    (errmsg("redo is not required")));
+       }
    }
 
    /*