Refactor code in charge of running shell-based recovery commands

The code specific to the execution of archive_cleanup_command,
recovery_end_command and restore_command is moved to a new file named
shell_restore.c.  The code is split into three functions:
- shell_restore(), that attempts the execution of a shell-based
restore_command.
- shell_archive_cleanup(), for archive_cleanup_command.
- shell_recovery_end(), for recovery_end_command.

This introduces no functional changes, with failure patterns and logs
generated in consequence being the same as before (one case actually
generates one less DEBUG2 message "could not restore" when a restore
command succeeds but the follow-up stat() to check the size fails, but
that only matters with a elevel high enough).

This is preparatory work for allowing recovery modules, a facility
similar to archive modules, with callbacks shaped similarly to the
functions introduced here.

Author: Nathan Bossart
Reviewed-by: Andres Freund, Michael Paquier
Discussion: https://postgr.es/m/20221227192449.GA3672473@nathanxps13

1 files changed, 29 insertions, 8 deletions

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 0070d56b0b0..8f47fb75700 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -692,6 +692,7 @@ static char *GetXLogBuffer(XLogRecPtr ptr, TimeLineID tli);
 static XLogRecPtr XLogBytePosToRecPtr(uint64 bytepos);
 static XLogRecPtr XLogBytePosToEndRecPtr(uint64 bytepos);
 static uint64 XLogRecPtrToBytePos(XLogRecPtr ptr);
+static void GetOldestRestartPointFileName(char *fname);
 
 static void WALInsertLockAcquire(void);
 static void WALInsertLockAcquireExclusive(void);
@@ -4887,10 +4888,12 @@ CleanupAfterArchiveRecovery(TimeLineID EndOfLogTLI, XLogRecPtr EndOfLog,
 	 * Execute the recovery_end_command, if any.
 	 */
 	if (recoveryEndCommand && strcmp(recoveryEndCommand, "") != 0)
-		ExecuteRecoveryCommand(recoveryEndCommand,
-							   "recovery_end_command",
-							   true,
-							   WAIT_EVENT_RECOVERY_END_COMMAND);
+	{
+		char		lastRestartPointFname[MAXFNAMELEN];
+
+		GetOldestRestartPointFileName(lastRestartPointFname);
+		shell_recovery_end(lastRestartPointFname);
+	}
 
 	/*
 	 * We switched to a new timeline. Clean up segments on the old timeline.
@@ -7307,10 +7310,12 @@ CreateRestartPoint(int flags)
 	 * Finally, execute archive_cleanup_command, if any.
 	 */
 	if (archiveCleanupCommand && strcmp(archiveCleanupCommand, "") != 0)
-		ExecuteRecoveryCommand(archiveCleanupCommand,
-							   "archive_cleanup_command",
-							   false,
-							   WAIT_EVENT_ARCHIVE_CLEANUP_COMMAND);
+	{
+		char		lastRestartPointFname[MAXFNAMELEN];
+
+		GetOldestRestartPointFileName(lastRestartPointFname);
+		shell_archive_cleanup(lastRestartPointFname);
+	}
 
 	return true;
 }
@@ -8884,6 +8889,22 @@ GetOldestRestartPoint(XLogRecPtr *oldrecptr, TimeLineID *oldtli)
 	LWLockRelease(ControlFileLock);
 }
 
+/*
+ * Returns the WAL file name for the last checkpoint or restartpoint.  This is
+ * the oldest WAL file that we still need if we have to restart recovery.
+ */
+static void
+GetOldestRestartPointFileName(char *fname)
+{
+	XLogRecPtr	restartRedoPtr;
+	TimeLineID	restartTli;
+	XLogSegNo	restartSegNo;
+
+	GetOldestRestartPoint(&restartRedoPtr, &restartTli);
+	XLByteToSeg(restartRedoPtr, restartSegNo, wal_segment_size);
+	XLogFileName(fname, restartTli, restartSegNo, wal_segment_size);
+}
+
 /* Thin wrapper around ShutdownWalRcv(). */
 void
 XLogShutdownWalRcv(void)