pg_rewind: Allow writing recovery configuration

This is provided with a new switch --write-recovery-conf and reuses the
pg_basebackup code.

Author: Paul Guo, Jimmy Yih, Ashwin Agrawal
Reviewed-by: Alexey Kondratov, Michaël Paquier, Álvaro Herrera
Discussion: https://postgr.es/m/CAEET0ZEffUkXc48pg2iqARQgGRYDiiVxDu+yYek_bTwJF+q=Uw@mail.gmail.com

doc/src/sgml/ref/pg_rewind.sgml

@@ -180,6 +180,19 @@ PostgreSQL documentation
       </listitem>
      </varlistentry>
 
+     <varlistentry>
+      <term><option>-R</option></term>
+      <term><option>--write-recovery-conf</option></term>
+      <listitem>
+       <para>
+        Create <filename>standby.signal</filename> and append connection
+        settings to <filename>postgresql.auto.conf</filename> in the output
+        directory.  <literal>--source-server</literal> is mandatory with
+        this option.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
       <term><option>-n</option></term>
       <term><option>--dry-run</option></term>

src/bin/pg_rewind/Makefile

@@ -16,7 +16,7 @@ top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
 override CPPFLAGS := -I$(libpq_srcdir) -DFRONTEND $(CPPFLAGS)
-LDFLAGS_INTERNAL += $(libpq_pgport)
+LDFLAGS_INTERNAL += $(libpq_pgport) -L$(top_builddir)/src/fe_utils -lpgfeutils
 
 OBJS	= pg_rewind.o parsexlog.o xlogreader.o datapagemap.o timeline.o \
 	fetch.o file_ops.o copy_fetch.o libpq_fetch.o filemap.o \

src/bin/pg_rewind/libpq_fetch.c

@@ -20,12 +20,11 @@
 #include "file_ops.h"
 #include "filemap.h"
 
-#include "libpq-fe.h"
 #include "catalog/pg_type_d.h"
 #include "fe_utils/connect.h"
 #include "port/pg_bswap.h"
 
-static PGconn *conn = NULL;
+PGconn *conn = NULL;
 
 /*
  * Files are fetched max CHUNKSIZE bytes at a time.

src/bin/pg_rewind/pg_rewind.c

@@ -27,6 +27,7 @@
 #include "common/file_perm.h"
 #include "common/file_utils.h"
 #include "common/restricted_token.h"
+#include "fe_utils/recovery_gen.h"
 #include "getopt_long.h"
 #include "storage/bufpage.h"
 
@@ -41,6 +42,7 @@ static void syncTargetDirectory(void);
 static void sanityChecks(void);
 static void findCommonAncestorTimeline(XLogRecPtr *recptr, int *tliIndex);
 static void ensureCleanShutdown(const char *argv0);
+static void disconnect_atexit(void);
 
 static ControlFileData ControlFile_target;
 static ControlFileData ControlFile_source;
@@ -76,6 +78,8 @@ usage(const char *progname)
 	printf(_("  -D, --target-pgdata=DIRECTORY  existing data directory to modify\n"));
 	printf(_("      --source-pgdata=DIRECTORY  source data directory to synchronize with\n"));
 	printf(_("      --source-server=CONNSTR    source server to synchronize with\n"));
+	printf(_("  -R, --write-recovery-conf      write configuration for replication\n"
+			 "                                 (requires --source-server)\n"));
 	printf(_("  -n, --dry-run                  stop before modifying anything\n"));
 	printf(_("  -N, --no-sync                  do not wait for changes to be written\n"
 			 "                                 safely to disk\n"));
@@ -94,6 +98,7 @@ main(int argc, char **argv)
 	static struct option long_options[] = {
 		{"help", no_argument, NULL, '?'},
 		{"target-pgdata", required_argument, NULL, 'D'},
+		{"write-recovery-conf", no_argument, NULL, 'R'},
 		{"source-pgdata", required_argument, NULL, 1},
 		{"source-server", required_argument, NULL, 2},
 		{"no-ensure-shutdown", no_argument, NULL, 44},
@@ -118,6 +123,7 @@ main(int argc, char **argv)
 	XLogRecPtr	endrec;
 	TimeLineID	endtli;
 	ControlFileData ControlFile_new;
+	bool		writerecoveryconf = false;
 
 	pg_logging_init(argv[0]);
 	set_pglocale_pgservice(argv[0], PG_TEXTDOMAIN("pg_rewind"));
@@ -138,7 +144,7 @@ main(int argc, char **argv)
 		}
 	}
 
-	while ((c = getopt_long(argc, argv, "D:nNP", long_options, &option_index)) != -1)
+	while ((c = getopt_long(argc, argv, "D:nNPR", long_options, &option_index)) != -1)
 	{
 		switch (c)
 		{
@@ -158,6 +164,10 @@ main(int argc, char **argv)
 				do_sync = false;
 				break;
 
+			case 'R':
+				writerecoveryconf = true;
+				break;
+
 			case 3:
 				debug = true;
 				pg_logging_set_level(PG_LOG_DEBUG);
@@ -200,6 +210,13 @@ main(int argc, char **argv)
 		exit(1);
 	}
 
+	if (writerecoveryconf && connstr_source == NULL)
+	{
+		pg_log_error("no source server information (--source--server) specified for --write-recovery-conf");
+		fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
+		exit(1);
+	}
+
 	if (optind < argc)
 	{
 		pg_log_error("too many command-line arguments (first is \"%s\")",
@@ -236,6 +253,8 @@ main(int argc, char **argv)
 
 	umask(pg_mode_mask);
 
+	atexit(disconnect_atexit);
+
 	/* Connect to remote server */
 	if (connstr_source)
 		libpqConnect(connstr_source);
@@ -322,6 +341,9 @@ main(int argc, char **argv)
 	if (!rewind_needed)
 	{
 		pg_log_info("no rewind required");
+		if (writerecoveryconf)
+			WriteRecoveryConfig(conn, datadir_target,
+								GenerateRecoveryConfig(conn, NULL));
 		exit(0);
 	}
 
@@ -419,6 +441,10 @@ main(int argc, char **argv)
 		pg_log_info("syncing target data directory");
 	syncTargetDirectory();
 
+	if (writerecoveryconf)
+		WriteRecoveryConfig(conn, datadir_target,
+							GenerateRecoveryConfig(conn, NULL));
+
 	pg_log_info("Done!");
 
 	return 0;
@@ -828,3 +854,10 @@ ensureCleanShutdown(const char *argv0)
 		pg_fatal("Command was: %s", cmd);
 	}
 }
+
+static void
+disconnect_atexit(void)
+{
+	if (conn != NULL)
+		PQfinish(conn);
+}

src/bin/pg_rewind/pg_rewind.h

@@ -14,10 +14,11 @@
 #include "datapagemap.h"
 
 #include "access/timeline.h"
+#include "common/logging.h"
+#include "libpq-fe.h"
 #include "storage/block.h"
 #include "storage/relfilenode.h"
 
-#include "common/logging.h"
 
 /* Configuration options */
 extern char *datadir_target;
@@ -31,6 +32,9 @@ extern int	WalSegSz;
 extern TimeLineHistoryEntry *targetHistory;
 extern int	targetNentries;
 
+/* general state */
+extern PGconn *conn;
+
 /* Progress counters */
 extern uint64 fetch_size;
 extern uint64 fetch_done;
@@ -53,6 +57,7 @@ extern void progress_report(bool force);
 
 /* in timeline.c */
 extern TimeLineHistoryEntry *rewind_parseTimeLineHistory(char *buffer,
-														 TimeLineID targetTLI, int *nentries);
+														 TimeLineID targetTLI,
+														 int *nentries);
 
 #endif							/* PG_REWIND_H */