On Thu, Oct 2, 2014 at 12:44 AM, Andres Freund <and...@2ndquadrant.com>
wrote:

> I pushed the first part.
>
Thanks. Attached is a rebased version of patch 2, implementing the actual
feature. One thing I noticed with more testing is that if --create is used
and that the destination folder does not exist, pg_receivexlog was creating
the slot, and left with an error. This does not look user-friendly so I
changed the logic a bit to check for the destination folder before creating
any slot. This results in a bit of refactoring, but this way behavior is
more intuitive.
Regards,
-- 
Michael
From e3ee4b918b8122d414c03207fdd50f2472dc292e Mon Sep 17 00:00:00 2001
From: Michael Paquier <mich...@otacoo.com>
Date: Mon, 1 Sep 2014 20:53:45 +0900
Subject: [PATCH] Support for replslot creation and drop in pg_receivexlog

Using the new actions --create and --drop that are similarly present
in pg_recvlogical, a user can respectively create and drop a replication
slot that can be used afterwards when fetching WALs.
---
 doc/src/sgml/ref/pg_receivexlog.sgml   |  29 +++++++
 src/bin/pg_basebackup/pg_receivexlog.c | 154 +++++++++++++++++++++++++++++----
 2 files changed, 168 insertions(+), 15 deletions(-)

diff --git a/doc/src/sgml/ref/pg_receivexlog.sgml b/doc/src/sgml/ref/pg_receivexlog.sgml
index 5916b8f..69aa0af 100644
--- a/doc/src/sgml/ref/pg_receivexlog.sgml
+++ b/doc/src/sgml/ref/pg_receivexlog.sgml
@@ -72,6 +72,35 @@ PostgreSQL documentation
   <title>Options</title>
 
    <para>
+    <application>pg_receivexlog</application> can run in one of two following
+    modes, which control physical replication slot:
+
+    <variablelist>
+
+     <varlistentry>
+      <term><option>--create</option></term>
+      <listitem>
+       <para>
+        Create a new physical replication slot with the name specified in
+        <option>--slot</option>.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
+      <term><option>--drop</option></term>
+      <listitem>
+       <para>
+        Drop the replication slot with the name specified in
+        <option>--slot</option>, then exit.
+       </para>
+      </listitem>
+     </varlistentry>
+    </variablelist>
+
+   </para>
+
+   <para>
     The following command-line options control the location and format of the
     output.
 
diff --git a/src/bin/pg_basebackup/pg_receivexlog.c b/src/bin/pg_basebackup/pg_receivexlog.c
index 171cf43..8c4f752 100644
--- a/src/bin/pg_basebackup/pg_receivexlog.c
+++ b/src/bin/pg_basebackup/pg_receivexlog.c
@@ -38,11 +38,15 @@ static int	noloop = 0;
 static int	standby_message_timeout = 10 * 1000;		/* 10 sec = default */
 static int	fsync_interval = 0; /* 0 = default */
 static volatile bool time_to_abort = false;
+static bool do_create_slot = false;
+static bool do_drop_slot = false;
 
 
 static void usage(void);
+static DIR* get_destination_dir(char *dest_folder);
+static void close_destination_dir(DIR *dest_dir, char *dest_folder);
 static XLogRecPtr FindStreamingStart(uint32 *tli);
-static void StreamLog();
+static void StreamLog(void);
 static bool stop_streaming(XLogRecPtr segendpos, uint32 timeline,
 			   bool segment_finished);
 
@@ -78,6 +82,9 @@ usage(void)
 	printf(_("  -w, --no-password      never prompt for password\n"));
 	printf(_("  -W, --password         force password prompt (should happen automatically)\n"));
 	printf(_("  -S, --slot=SLOTNAME    replication slot to use\n"));
+	printf(_("\nOptional actions:\n"));
+	printf(_("      --create           create a new replication slot (for the slot's name see --slot)\n"));
+	printf(_("      --drop             drop the replication slot (for the slot's name see --slot)\n"));
 	printf(_("\nReport bugs to <pgsql-b...@postgresql.org>.\n"));
 }
 
@@ -118,6 +125,44 @@ stop_streaming(XLogRecPtr xlogpos, uint32 timeline, bool segment_finished)
 	return false;
 }
 
+
+/*
+ * Get destination directory.
+ */
+static DIR*
+get_destination_dir(char *dest_folder)
+{
+	DIR *dir;
+
+	Assert(dest_folder != NULL);
+	dir = opendir(dest_folder);
+	if (dir == NULL)
+	{
+		fprintf(stderr, _("%s: could not open directory \"%s\": %s\n"),
+				progname, basedir, strerror(errno));
+		disconnect_and_exit(1);
+	}
+
+	return dir;
+}
+
+
+/*
+ * Close existing directory.
+ */
+static void
+close_destination_dir(DIR *dest_dir, char *dest_folder)
+{
+	Assert(dest_dir != NULL && dest_folder != NULL);
+	if (closedir(dest_dir))
+	{
+		fprintf(stderr, _("%s: could not close directory \"%s\": %s\n"),
+				progname, dest_folder, strerror(errno));
+		disconnect_and_exit(1);
+	}
+}
+
+
 /*
  * Determine starting location for streaming, based on any existing xlog
  * segments in the directory. We start at the end of the last one that is
@@ -134,13 +179,7 @@ FindStreamingStart(uint32 *tli)
 	uint32		high_tli = 0;
 	bool		high_ispartial = false;
 
-	dir = opendir(basedir);
-	if (dir == NULL)
-	{
-		fprintf(stderr, _("%s: could not open directory \"%s\": %s\n"),
-				progname, basedir, strerror(errno));
-		disconnect_and_exit(1);
-	}
+	dir = get_destination_dir(basedir);
 
 	while (errno = 0, (dirent = readdir(dir)) != NULL)
 	{
@@ -219,12 +258,7 @@ FindStreamingStart(uint32 *tli)
 		disconnect_and_exit(1);
 	}
 
-	if (closedir(dir))
-	{
-		fprintf(stderr, _("%s: could not close directory \"%s\": %s\n"),
-				progname, basedir, strerror(errno));
-		disconnect_and_exit(1);
-	}
+	close_destination_dir(dir, basedir);
 
 	if (high_segno > 0)
 	{
@@ -344,11 +378,15 @@ main(int argc, char **argv)
 		{"status-interval", required_argument, NULL, 's'},
 		{"slot", required_argument, NULL, 'S'},
 		{"verbose", no_argument, NULL, 'v'},
+/* action */
+		{"create", no_argument, NULL, 1},
+		{"drop", no_argument, NULL, 2},
 		{NULL, 0, NULL, 0}
 	};
 
 	int			c;
 	int			option_index;
+	char	   *db_name;
 
 	progname = get_progname(argv[0]);
 	set_pglocale_pgservice(argv[0], PG_TEXTDOMAIN("pg_receivexlog"));
@@ -427,6 +465,13 @@ main(int argc, char **argv)
 			case 'v':
 				verbose++;
 				break;
+/* action */
+			case 1:
+				do_create_slot = true;
+				break;
+			case 2:
+				do_drop_slot = true;
+				break;
 			default:
 
 				/*
@@ -451,10 +496,26 @@ main(int argc, char **argv)
 		exit(1);
 	}
 
+	if (replication_slot == NULL && (do_drop_slot || do_create_slot))
+	{
+		fprintf(stderr, _("%s: replication slot needed with action --create or --drop\n"), progname);
+		fprintf(stderr, _("Try \"%s --help\" for more information.\n"),
+				progname);
+		exit(1);
+	}
+
+	if (do_drop_slot && do_create_slot)
+	{
+		fprintf(stderr, _("%s: cannot use --create together with --drop\n"), progname);
+		fprintf(stderr, _("Try \"%s --help\" for more information.\n"),
+				progname);
+		exit(1);
+	}
+
 	/*
 	 * Required arguments
 	 */
-	if (basedir == NULL)
+	if (basedir == NULL && !do_drop_slot)
 	{
 		fprintf(stderr, _("%s: no target directory specified\n"), progname);
 		fprintf(stderr, _("Try \"%s --help\" for more information.\n"),
@@ -462,10 +523,73 @@ main(int argc, char **argv)
 		exit(1);
 	}
 
+	/*
+	 * Check existence of destination folder.
+	 */
+	if (!do_drop_slot)
+	{
+		DIR *dir = get_destination_dir(basedir);
+		close_destination_dir(dir, basedir);
+	}
+
 #ifndef WIN32
 	pqsignal(SIGINT, sigint_handler);
 #endif
 
+	/*
+	 * Obtain a connection before doing anything.
+	 */
+	conn = GetConnection();
+	if (!conn)
+		/* error message already written in GetConnection() */
+		exit(1);
+
+	/*
+	 * Run IDENTIFY_SYSTEM so we can get the timeline and current xlog
+	 * position.
+	 */
+	if (!RunIdentifySystem(conn, NULL, NULL, NULL, &db_name))
+		disconnect_and_exit(1);
+
+	/*
+	 * Check that there is a database associated with connection, none
+	 * should be defined in this context.
+	 */
+	if (db_name)
+	{
+		fprintf(stderr,
+				_("%s: database defined for replication connection \"%s\"\n"),
+				progname, replication_slot);
+		disconnect_and_exit(1);
+	}
+
+	/*
+	 * Drop a replication slot.
+	 */
+	if (do_drop_slot)
+	{
+		if (verbose)
+			fprintf(stderr,
+					_("%s: dropping replication slot \"%s\"\n"),
+					progname, replication_slot);
+
+		if (!DropReplicationSlot(conn, replication_slot))
+			disconnect_and_exit(1);
+		disconnect_and_exit(0);
+	}
+
+	/* Create a replication slot */
+	if (do_create_slot)
+	{
+		if (verbose)
+			fprintf(stderr,
+					_("%s: creating replication slot \"%s\"\n"),
+					progname, replication_slot);
+
+		if (!CreateReplicationSlot(conn, replication_slot, NULL, NULL, true))
+			disconnect_and_exit(1);
+	}
+
 	while (true)
 	{
 		StreamLog();
-- 
2.1.1

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