send pg_stop_backup() asynchronously, cancel query if no answer in 300 seconds

alubennikova · alubennikova · commit ab3b160a1a34 · 2017-06-14T19:30:25.000+03:00
diff --git a/backup.c b/backup.c
@@ -909,6 +909,9 @@ pg_stop_backup(pgBackup *backup)
 	uint32		xlogid;
 	uint32		xrecoff;
 	XLogRecPtr	restore_lsn;
+	bool sent = false;
+	int pg_stop_backup_timeout = 0;
+	int is_busy = 1;
 
 	/*
 	 * We will use this values if there are no transactions between start_lsn
@@ -999,23 +1002,72 @@ pg_stop_backup(pgBackup *backup)
 		pfree(backup_id);
 	}
 
+	/*
+	 * send pg_stop_backup asynchronously because we could came
+	 * here from backup_cleanup() after some error caused by
+	 * postgres archive_command problem and in this case we will
+	 * wait for pg_stop_backup() forever.
+	 */
 	if (!exclusive_backup)
 		/*
 		 * Stop the non-exclusive backup. Besides stop_lsn it returns from
 		 * pg_stop_backup(false) copy of the backup label and tablespace map
 		 * so they can be written to disk by the caller.
 		 */
-		res = pgut_execute(backup_conn,
+		sent = pgut_send(backup_conn,
 						   "SELECT *, txid_snapshot_xmax(txid_current_snapshot()),"
 						   " current_timestamp(0)::timestamp"
 						   " FROM pg_stop_backup(false)",
-						   0, NULL);
+						   0, NULL, WARNING);
 	else
-		res = pgut_execute(backup_conn,
+		sent = pgut_send(backup_conn,
 						   "SELECT *, txid_snapshot_xmax(txid_current_snapshot()),"
 						   " current_timestamp(0)::timestamp"
 						   " FROM pg_stop_backup()",
-						   0, NULL);
+						   0, NULL, WARNING);
+
+	if (!sent)
+		elog(WARNING, "Failed to send pg_stop_backup query");
+
+
+	/*
+	 * Wait for the result of pg_stop_backup(),
+	 * but no longer than PG_STOP_BACKUP_TIMEOUT seconds
+	 */
+	elog(INFO, "wait for pg_stop_backup()");
+	do
+	{
+		/*
+		 * PQisBusy returns 1 if a command is busy, that is, PQgetResult would
+		 * block waiting for input. A 0 return indicates that PQgetResult can
+		 * be called with assurance of not blocking
+		 */
+		is_busy = PQisBusy(backup_conn);
+		pg_stop_backup_timeout++;
+		sleep(1);
+
+		if (interrupted)
+		{
+			pgut_cancel(backup_conn);
+			elog(ERROR, "interrupted during waiting for pg_stop_backup");
+		}
+
+	} while (is_busy && pg_stop_backup_timeout < PG_STOP_BACKUP_TIMEOUT);
+
+	/*
+	 * If postgres haven't answered in PG_STOP_BACKUP_TIMEOUT seconds,
+	 * send an interrupt.
+	 */
+	if (is_busy)
+	{
+		pgut_cancel(backup_conn);
+		elog(ERROR, "pg_stop_backup doesn't finish in 300 seconds.");
+	}
+
+	res = PQgetResult(backup_conn);
+
+	if (!res)
+		elog(ERROR, "pg_stop backup() failed");
 
 	backup_in_progress = false;
 
diff --git a/data.c b/data.c
@@ -570,8 +570,6 @@ restore_data_file(const char *from_root,
 			if (uncompressed_size != BLCKSZ)
 				elog(ERROR, "page uncompressed to %ld bytes. != BLCKSZ", uncompressed_size);
 		}
-		else
-			memcpy(page.data, compressed_page.data, BLCKSZ);
 
 		/*
 		 * Seek and write the restored page.
@@ -580,9 +578,20 @@ restore_data_file(const char *from_root,
 		if (fseek(out, blknum * BLCKSZ, SEEK_SET) < 0)
 			elog(ERROR, "cannot seek block %u of \"%s\": %s",
 				 blknum, to_path, strerror(errno));
-		if (fwrite(page.data, 1, sizeof(page), out) != sizeof(page))
-			elog(ERROR, "cannot write block %u of \"%s\": %s",
-				 blknum, file->path, strerror(errno));
+
+		if (header.compressed_size < BLCKSZ)
+		{
+			if (fwrite(page.data, 1, BLCKSZ, out) != BLCKSZ)
+				elog(ERROR, "cannot write block %u of \"%s\": %s",
+					blknum, file->path, strerror(errno));
+		}
+		else
+		{
+			/* if page wasn't compressed, we've read full block */
+			if (fwrite(compressed_page.data, 1, BLCKSZ, out) != BLCKSZ)
+				elog(ERROR, "cannot write block %u of \"%s\": %s",
+					blknum, file->path, strerror(errno));
+		}
 	}
 
 	/* update file permission */
diff --git a/pg_probackup.h b/pg_probackup.h
@@ -33,6 +33,7 @@
 
 #include "datapagemap.h"
 
+# define PG_STOP_BACKUP_TIMEOUT 300
 /*
  * Macro needed to parse ptrack.
  * NOTE Keep those values syncronised with definitions in ptrack.h
diff --git a/utils/pgut.c b/utils/pgut.c
@@ -1174,6 +1174,24 @@ pgut_send(PGconn* conn, const char *query, int nParams, const char **params, int
 	return true;
 }
 
+void
+pgut_cancel(PGconn* conn)
+{
+	PGcancel *cancel_conn = PQgetCancel(conn);
+	char		errbuf[256];
+
+	if (cancel_conn != NULL)
+	{
+		if (PQcancel(cancel_conn, errbuf, sizeof(errbuf)))
+			elog(WARNING, "Cancel request sent");
+		else
+			elog(WARNING, "Cancel request failed");
+	}
+
+	if (cancel_conn)
+		PQfreeCancel(cancel_conn);
+}
+
 int
 pgut_wait(int num, PGconn *connections[], struct timeval *timeout)
 {
diff --git a/utils/pgut.h b/utils/pgut.h
@@ -122,6 +122,7 @@ extern PGconn *pgut_connect_extended(const char *pghost, const char *pgport,
 extern void pgut_disconnect(PGconn *conn);
 extern PGresult *pgut_execute(PGconn* conn, const char *query, int nParams, const char **params);
 extern bool pgut_send(PGconn* conn, const char *query, int nParams, const char **params, int elevel);
+extern void pgut_cancel(PGconn* conn);
 extern int pgut_wait(int num, PGconn *connections[], struct timeval *timeout);
 
 extern const char *pgut_get_host(void);
