Hi,

Am Dienstag, den 21.03.2017, 11:03 +0900 schrieb Michael Paquier:
> On Tue, Mar 21, 2017 at 1:32 AM, Michael Banck
> <michael.ba...@credativ.de> wrote:
>      /*
> +     * Try to create a permanent replication slot if one is specified. Do
> +     * not error out if the slot already exists, other errors are already
> +     * reported by CreateReplicationSlot().
> +     */
> +    if (!stream->temp_slot && stream->replication_slot)
> +    {
> +        if (!CreateReplicationSlot(conn, stream->replication_slot,
> NULL, true, true))
> +            return false;
> +    }
> This could be part of an else taken from the previous if where
> temp_slot is checked.

Not sure how this would work, as ISTM the if clause above only sets the
name for param->temp_slot (if supported), but doesn't distinguish which
kind of slot (if any) will actually be created. 

I've done it for the second (refactoring) patch though, but I had to
make `no_slot' a global variable to not have the logic be too
complicated.

> There should be some TAP tests included. And +1 for sharing the same
> behavior as pg_receivewal.

Well, I've adjusted the TAP tests in so far as it's now checking that
the physical slot got created, previously it checked for the opposite:

|-$node->command_fails(
|+$node->command_ok(
|        [   'pg_basebackup',             '-D',
|                "$tempdir/backupxs_sl_fail", '-X',
|                'stream',                    '-S',
|-               'slot1' ],
|-       'pg_basebackup fails with nonexistent replication slot');
|+               'slot0' ],
|+       'pg_basebackup runs with nonexistent replication slot');
|+
|+my $lsn = $node->safe_psql('postgres',
|+       q{SELECT restart_lsn FROM pg_replication_slots WHERE slot_name
|= 'slot0'}
|+);
|+like($lsn, qr!^0/[0-9A-F]{7,8}$!, 'slot is present');

I have now made the message a bit clearer by saying "pg_basebackup -S
creates previously nonexistent replication slot".

Probably there could be additional TAP tests, but off the top of my head
I can't think of any?

New patches attached.


Michael

-- 
Michael Banck
Projektleiter / Senior Berater
Tel.: +49 2166 9901-171
Fax:  +49 2166 9901-100
Email: michael.ba...@credativ.de

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From 93337fe0ef320fe8ef68a9b64c4df85a63c4346c Mon Sep 17 00:00:00 2001
From: Michael Banck <michael.ba...@credativ.de>
Date: Sun, 19 Mar 2017 10:58:13 +0100
Subject: [PATCH 1/2] Create replication slot in pg_basebackup if requested and
 not yet present.

If a replication slot is explicitly requested, try to create it before
starting to replicate from it.
---
 src/bin/pg_basebackup/pg_basebackup.c        | 15 +++++++++++++++
 src/bin/pg_basebackup/t/010_pg_basebackup.pl | 19 ++++++++++++-------
 2 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/src/bin/pg_basebackup/pg_basebackup.c b/src/bin/pg_basebackup/pg_basebackup.c
index 0a4944d..69ca4be 100644
--- a/src/bin/pg_basebackup/pg_basebackup.c
+++ b/src/bin/pg_basebackup/pg_basebackup.c
@@ -581,6 +581,21 @@ StartLogStreamer(char *startpos, uint32 timeline, char *sysidentifier)
 	else
 		param->temp_slot = temp_replication_slot;
 
+	/*
+	 * Try to create a permanent replication slot if one is specified. Do
+	 * not error out if the slot already exists, other errors are already
+	 * reported by CreateReplicationSlot().
+	 */
+	if (!temp_replication_slot && replication_slot)
+	{
+		if (verbose)
+			fprintf(stderr, _("%s: creating replication slot \"%s\"\n"),
+					progname, replication_slot);
+
+		if (!CreateReplicationSlot(param->bgconn, replication_slot, NULL, true, true))
+			return 1;
+	}
+
 	if (format == 'p')
 	{
 		/*
diff --git a/src/bin/pg_basebackup/t/010_pg_basebackup.pl b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
index 14bd813..f50005f 100644
--- a/src/bin/pg_basebackup/t/010_pg_basebackup.pl
+++ b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
@@ -4,7 +4,7 @@ use Cwd;
 use Config;
 use PostgresNode;
 use TestLib;
-use Test::More tests => 72;
+use Test::More tests => 73;
 
 program_help_ok('pg_basebackup');
 program_version_ok('pg_basebackup');
@@ -246,17 +246,22 @@ $node->command_ok(
 	'pg_basebackup -X stream runs with --no-slot');
 
 $node->command_fails(
-	[ 'pg_basebackup', '-D', "$tempdir/fail", '-S', 'slot1' ],
+	[ 'pg_basebackup', '-D', "$tempdir/fail", '-X', 'none', '-S', 'slot0' ],
 	'pg_basebackup with replication slot fails without -X stream');
-$node->command_fails(
+$node->command_ok(
 	[   'pg_basebackup',             '-D',
 		"$tempdir/backupxs_sl_fail", '-X',
 		'stream',                    '-S',
-		'slot1' ],
-	'pg_basebackup fails with nonexistent replication slot');
+		'slot0' ],
+	'pg_basebackup -S creates previously nonexistent replication slot');
+
+my $lsn = $node->safe_psql('postgres',
+	q{SELECT restart_lsn FROM pg_replication_slots WHERE slot_name = 'slot0'}
+);
+like($lsn, qr!^0/[0-9A-F]{7,8}$!, 'slot is present');
 
 $node->safe_psql('postgres',
-	q{SELECT * FROM pg_create_physical_replication_slot('slot1')});
+       q{SELECT * FROM pg_create_physical_replication_slot('slot1')});
 my $lsn = $node->safe_psql('postgres',
 	q{SELECT restart_lsn FROM pg_replication_slots WHERE slot_name = 'slot1'}
 );
@@ -268,7 +273,7 @@ $node->command_ok(
 $lsn = $node->safe_psql('postgres',
 	q{SELECT restart_lsn FROM pg_replication_slots WHERE slot_name = 'slot1'}
 );
-like($lsn, qr!^0/[0-9A-Z]{7,8}$!, 'restart LSN of slot has advanced');
+like($lsn, qr!^0/[0-9A-F]{7,8}$!, 'restart LSN of slot has advanced');
 
 $node->command_ok(
 	[   'pg_basebackup', '-D', "$tempdir/backupxs_sl_R", '-X',
-- 
2.1.4

From e4bd7b0a40ced05efbd2740b5b4f8ed6b08eae6c Mon Sep 17 00:00:00 2001
From: Michael Banck <michael.ba...@credativ.de>
Date: Tue, 21 Mar 2017 12:50:22 +0100
Subject: [PATCH 2/2] Refactor replication slot creation in pg_basebackup et
 al.

Add new argument `is_temporary' to CreateReplicationSlot() in streamutil.c
which specifies whether a physical replication slot is temporary or not. Update
all callers.

Move the creation of the temporary replication slot for pg_basebackup from
receivelog.c to pg_basebackup.c. At the same time, also create the temporary
slot via CreateReplicationSlot() instead of creating the temporary slot with an
explicit SQL command.
---
 src/bin/pg_basebackup/pg_basebackup.c  | 28 +++++++++++++++++-----------
 src/bin/pg_basebackup/pg_receivewal.c  |  2 +-
 src/bin/pg_basebackup/pg_recvlogical.c |  2 +-
 src/bin/pg_basebackup/receivelog.c     | 18 ------------------
 src/bin/pg_basebackup/streamutil.c     | 18 +++++++++++++-----
 src/bin/pg_basebackup/streamutil.h     |  2 +-
 6 files changed, 33 insertions(+), 37 deletions(-)

diff --git a/src/bin/pg_basebackup/pg_basebackup.c b/src/bin/pg_basebackup/pg_basebackup.c
index 69ca4be..c7ae281 100644
--- a/src/bin/pg_basebackup/pg_basebackup.c
+++ b/src/bin/pg_basebackup/pg_basebackup.c
@@ -92,6 +92,7 @@ static pg_time_t last_progress_report = 0;
 static int32 maxrate = 0;		/* no limit by default */
 static char *replication_slot = NULL;
 static bool temp_replication_slot = true;
+static bool no_slot = false;
 
 static bool success = false;
 static bool made_new_pgdata = false;
@@ -487,8 +488,6 @@ LogStreamerMain(logstreamer_param *param)
 	stream.partial_suffix = NULL;
 	stream.replication_slot = replication_slot;
 	stream.temp_slot = param->temp_slot;
-	if (stream.temp_slot && !stream.replication_slot)
-		stream.replication_slot = psprintf("pg_basebackup_%d", (int) getpid());
 
 	if (format == 'p')
 		stream.walmethod = CreateWalDirectoryMethod(param->xlog, 0, do_sync);
@@ -582,18 +581,26 @@ StartLogStreamer(char *startpos, uint32 timeline, char *sysidentifier)
 		param->temp_slot = temp_replication_slot;
 
 	/*
-	 * Try to create a permanent replication slot if one is specified. Do
-	 * not error out if the slot already exists, other errors are already
-	 * reported by CreateReplicationSlot().
+	 * Create replication slot if one is needed.
 	 */
-	if (!temp_replication_slot && replication_slot)
+	if (!no_slot)
 	{
+		if (!replication_slot)
+			replication_slot = psprintf("pg_basebackup_%d", (int) getpid());
+
 		if (verbose)
-			fprintf(stderr, _("%s: creating replication slot \"%s\"\n"),
-					progname, replication_slot);
+		{
+			if (temp_replication_slot)
+				fprintf(stderr, _("%s: creating temporary replication slot \"%s\"\n"),
+						progname, replication_slot);
+			else
+				fprintf(stderr, _("%s: creating replication slot \"%s\"\n"),
+						progname, replication_slot);
+		}
 
-		if (!CreateReplicationSlot(param->bgconn, replication_slot, NULL, true, true))
-			return 1;
+		if (!CreateReplicationSlot(param->bgconn, replication_slot, NULL, true,
+								   temp_replication_slot, true))
+			disconnect_and_exit(1);
 	}
 
 	if (format == 'p')
@@ -2110,7 +2117,6 @@ main(int argc, char **argv)
 	int			c;
 
 	int			option_index;
-	bool		no_slot = false;
 
 	progname = get_progname(argv[0]);
 	set_pglocale_pgservice(argv[0], PG_TEXTDOMAIN("pg_basebackup"));
diff --git a/src/bin/pg_basebackup/pg_receivewal.c b/src/bin/pg_basebackup/pg_receivewal.c
index 15348ad..d221633 100644
--- a/src/bin/pg_basebackup/pg_receivewal.c
+++ b/src/bin/pg_basebackup/pg_receivewal.c
@@ -699,7 +699,7 @@ main(int argc, char **argv)
 					progname, replication_slot);
 
 		if (!CreateReplicationSlot(conn, replication_slot, NULL, true,
-								   slot_exists_ok))
+								   false, slot_exists_ok))
 			disconnect_and_exit(1);
 		disconnect_and_exit(0);
 	}
diff --git a/src/bin/pg_basebackup/pg_recvlogical.c b/src/bin/pg_basebackup/pg_recvlogical.c
index 6b081bd..14ce537 100644
--- a/src/bin/pg_basebackup/pg_recvlogical.c
+++ b/src/bin/pg_basebackup/pg_recvlogical.c
@@ -980,7 +980,7 @@ main(int argc, char **argv)
 					progname, replication_slot);
 
 		if (!CreateReplicationSlot(conn, replication_slot, plugin,
-								   false, slot_exists_ok))
+								   false, false, slot_exists_ok))
 			disconnect_and_exit(1);
 		startpos = InvalidXLogRecPtr;
 	}
diff --git a/src/bin/pg_basebackup/receivelog.c b/src/bin/pg_basebackup/receivelog.c
index f415135..d884793 100644
--- a/src/bin/pg_basebackup/receivelog.c
+++ b/src/bin/pg_basebackup/receivelog.c
@@ -509,24 +509,6 @@ ReceiveXlogStream(PGconn *conn, StreamCtl *stream)
 	}
 
 	/*
-	 * Create temporary replication slot if one is needed
-	 */
-	if (stream->temp_slot)
-	{
-		snprintf(query, sizeof(query),
-			 "CREATE_REPLICATION_SLOT \"%s\" TEMPORARY PHYSICAL RESERVE_WAL",
-				 stream->replication_slot);
-		res = PQexec(conn, query);
-		if (PQresultStatus(res) != PGRES_TUPLES_OK)
-		{
-			fprintf(stderr, _("%s: could not create temporary replication slot \"%s\": %s"),
-					progname, stream->replication_slot, PQerrorMessage(conn));
-			PQclear(res);
-			return false;
-		}
-	}
-
-	/*
 	 * initialize flush position to starting point, it's the caller's
 	 * responsibility that that's sane.
 	 */
diff --git a/src/bin/pg_basebackup/streamutil.c b/src/bin/pg_basebackup/streamutil.c
index 507da5e..67d801a 100644
--- a/src/bin/pg_basebackup/streamutil.c
+++ b/src/bin/pg_basebackup/streamutil.c
@@ -322,7 +322,7 @@ RunIdentifySystem(PGconn *conn, char **sysid, TimeLineID *starttli,
  */
 bool
 CreateReplicationSlot(PGconn *conn, const char *slot_name, const char *plugin,
-					  bool is_physical, bool slot_exists_ok)
+					  bool is_physical, bool is_temporary, bool slot_exists_ok)
 {
 	PQExpBuffer query;
 	PGresult   *res;
@@ -335,12 +335,20 @@ CreateReplicationSlot(PGconn *conn, const char *slot_name, const char *plugin,
 
 	/* Build query */
 	if (is_physical)
-		appendPQExpBuffer(query, "CREATE_REPLICATION_SLOT \"%s\" PHYSICAL",
-						  slot_name);
+		if (is_temporary)
+			appendPQExpBuffer(query, "CREATE_REPLICATION_SLOT \"%s\" TEMPORARY PHYSICAL",
+							  slot_name);
+		else
+			appendPQExpBuffer(query, "CREATE_REPLICATION_SLOT \"%s\" PHYSICAL",
+							  slot_name);
 	else
 	{
-		appendPQExpBuffer(query, "CREATE_REPLICATION_SLOT \"%s\" LOGICAL \"%s\"",
-						  slot_name, plugin);
+		if (is_temporary)
+			appendPQExpBuffer(query, "CREATE_REPLICATION_SLOT \"%s\" TEMPORARY LOGICAL \"%s\"",
+							  slot_name, plugin);
+		else
+			appendPQExpBuffer(query, "CREATE_REPLICATION_SLOT \"%s\" LOGICAL \"%s\"",
+							  slot_name, plugin);
 		if (PQserverVersion(conn) >= 100000)
 			/* pg_recvlogical doesn't use an exported snapshot, so suppress */
 			appendPQExpBuffer(query, " NOEXPORT_SNAPSHOT");
diff --git a/src/bin/pg_basebackup/streamutil.h b/src/bin/pg_basebackup/streamutil.h
index 460dcb5..1fe4168 100644
--- a/src/bin/pg_basebackup/streamutil.h
+++ b/src/bin/pg_basebackup/streamutil.h
@@ -32,7 +32,7 @@ extern PGconn *GetConnection(void);
 
 /* Replication commands */
 extern bool CreateReplicationSlot(PGconn *conn, const char *slot_name,
-					  const char *plugin, bool is_physical,
+					  const char *plugin, bool is_physical, bool is_temporary,
 					  bool slot_exists_ok);
 extern bool DropReplicationSlot(PGconn *conn, const char *slot_name);
 extern bool RunIdentifySystem(PGconn *conn, char **sysid,
-- 
2.1.4

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