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walreceiver uses a temporary replication slot by default

author Peter Eisentraut <peter@eisentraut.org>

2020年1月14日 13:07:11 +0000 (14:07 +0100)

committer Peter Eisentraut <peter@eisentraut.org>

2020年1月14日 13:40:41 +0000 (14:40 +0100)

If no permanent replication slot is configured using
primary_slot_name, the walreceiver now creates and uses a temporary
replication slot. A new setting wal_receiver_create_temp_slot can be
used to disable this behavior, for example, if the remote instance is
out of replication slots.

Reviewed-by: Masahiko Sawada <masahiko.sawada@2ndquadrant.com>
Discussion: https://www.postgresql.org/message-id/CA%2Bfd4k4dM0iEPLxyVyme2RAFsn8SUgrNtBJOu81YqTY4V%2BnqZA%40mail.gmail.com

doc/src/sgml/config.sgml patch | blob | blame | history

src/backend/replication/libpqwalreceiver/libpqwalreceiver.c patch | blob | blame | history

src/backend/replication/walreceiver.c patch | blob | blame | history

src/backend/utils/misc/guc.c patch | blob | blame | history

src/backend/utils/misc/postgresql.conf.sample patch | blob | blame | history

src/include/replication/walreceiver.h patch | blob | blame | history

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml

index 5d1c90282f949e229f9318a90f5a3a19e72b938b..5d45b6f7cba7c86d4fdfb9ad39971b9f9c2f6a85 100644 (file)

--- a/doc/src/sgml/config.sgml

+++ b/doc/src/sgml/config.sgml

@@ -4124,6 +4124,26 @@ ANY <replaceable class="parameter">num_sync</replaceable> ( <replaceable class="

</listitem>

</varlistentry>

+ <varlistentry id="guc-wal-receiver-create-temp-slot" xreflabel="wal_receiver_create_temp_slot">

+ <term><varname>wal_receiver_create_temp_slot</varname> (<type>boolean</type>)

+ <indexterm>

+ <primary><varname>wal_receiver_create_temp_slot</varname> configuration parameter</primary>

+ </indexterm>

+ </term>

+ <listitem>

+ <para>

+ Specifies whether a WAL receiver should create a temporary replication

+ slot on the remote instance when no permanent replication slot to use

+ has been configured (using <xref linkend="guc-primary-slot-name"/>).

+ The default is on. The only reason to turn this off would be if the

+ remote instance is currently out of available replication slots. This

+ parameter can only be set in the <filename>postgresql.conf</filename>

+ file or on the server command line. Changes only take effect when the

+ WAL receiver process starts a new connection.

+ </para>

+ </listitem>

+ </varlistentry>

<term><varname>wal_receiver_status_interval</varname> (<type>integer</type>)

diff --git a/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c

index b731d3fd04e2cc986d9c486b6f632332a02f95ed..e4fd1f9bb6f0df4a8f0b5713eade8532d1111814 100644 (file)

--- a/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c

+++ b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c

@@ -834,6 +834,10 @@ libpqrcv_create_slot(WalReceiverConn *conn, const char *slotname,

break;

}

+ else

+ {

+ appendStringInfoString(&cmd, " PHYSICAL RESERVE_WAL");

+ }

res = libpqrcv_PQexec(conn->streamConn, cmd.data);

pfree(cmd.data);

diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c

index 77360f1524b4a159256fe3f7f0a8958284044525..b46411433395843e6266d1730399d0e4c373c543 100644 (file)

--- a/src/backend/replication/walreceiver.c

+++ b/src/backend/replication/walreceiver.c

@@ -73,6 +73,7 @@

/* GUC variables */

+bool wal_receiver_create_temp_slot;

int wal_receiver_status_interval;

int wal_receiver_timeout;

bool hot_standby_feedback;

@@ -169,6 +170,7 @@ WalReceiverMain(void)

char conninfo[MAXCONNINFO];

char *tmp_conninfo;

char slotname[NAMEDATALEN];

+ bool is_temp_slot;

XLogRecPtr startpoint;

TimeLineID startpointTLI;

TimeLineID primaryTLI;

@@ -230,6 +232,7 @@ WalReceiverMain(void)

walrcv->ready_to_display = false;

strlcpy(conninfo, (char *) walrcv->conninfo, MAXCONNINFO);

strlcpy(slotname, (char *) walrcv->slotname, NAMEDATALEN);

+ is_temp_slot = walrcv->is_temp_slot;

startpoint = walrcv->receiveStart;

startpointTLI = walrcv->receiveStartTLI;

@@ -345,6 +348,44 @@ WalReceiverMain(void)

WalRcvFetchTimeLineHistoryFiles(startpointTLI, primaryTLI);

+ /*

+ * Create temporary replication slot if no slot name is configured or

+ * the slot from the previous run was temporary, unless

+ * wal_receiver_create_temp_slot is disabled. We also need to handle

+ * the case where the previous run used a temporary slot but

+ * wal_receiver_create_temp_slot was changed in the meantime. In that

+ * case, we delete the old slot name in shared memory. (This would

+ * all be a bit easier if we just didn't copy the slot name into

+ * shared memory, since we won't need it again later, but then we

+ * can't see the slot name in the stats views.)

+ */

+ if (slotname[0] == '0円' || is_temp_slot)

+ {

+ bool changed = false;

+ if (wal_receiver_create_temp_slot)

+ {

+ snprintf(slotname, sizeof(slotname),

+ "pg_walreceiver_%d", walrcv_get_backend_pid(wrconn));

+ walrcv_create_slot(wrconn, slotname, true, 0, NULL);

+ changed = true;

+ }

+ else if (slotname[0] != '0円')

+ {

+ slotname[0] = '0円';

+ changed = true;

+ }

+ if (changed)

+ {

+ SpinLockAcquire(&walrcv->mutex);

+ strlcpy(walrcv->slotname, slotname, NAMEDATALEN);

+ walrcv->is_temp_slot = wal_receiver_create_temp_slot;

+ SpinLockRelease(&walrcv->mutex);

+ }

* Start streaming.

diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c

index 62285792ecafe5a82f55d8a63a8170662d8a4ea2..e5f8a1301faa3a33f1461029131245792466bd7b 100644 (file)

--- a/src/backend/utils/misc/guc.c

+++ b/src/backend/utils/misc/guc.c

@@ -1969,6 +1969,15 @@ static struct config_bool ConfigureNamesBool[] =

NULL, NULL, NULL

+ {

+ {"wal_receiver_create_temp_slot", PGC_SIGHUP, REPLICATION_STANDBY,

+ gettext_noop("Sets whether a WAL receiver should create a temporary replication slot if no permanent slot is configured."),

+ },

+ &wal_receiver_create_temp_slot,

+ true,

+ NULL, NULL, NULL

+ },

/* End-of-list marker */

{

{NULL, 0, 0, NULL, NULL}, NULL, false, NULL, NULL, NULL

diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample

index 087190ce6383fc349423acd4f039d02c3084e646..e1048c0047b88f04ff773fdfb47292a05a9a983b 100644 (file)

--- a/src/backend/utils/misc/postgresql.conf.sample

+++ b/src/backend/utils/misc/postgresql.conf.sample

@@ -321,6 +321,7 @@

#max_standby_streaming_delay = 30s # max delay before canceling queries

# when reading streaming WAL;

# -1 allows indefinite delay

+#wal_receiver_create_temp_slot = on # create temp slot if primary_slot_name not set

#wal_receiver_status_interval = 10s # send replies at least this often

# 0 disables

#hot_standby_feedback = off # send info from standby to prevent

diff --git a/src/include/replication/walreceiver.h b/src/include/replication/walreceiver.h

index 172cfa28629c1ea7715ab18d2cb644f35068504c..e08afc6548f8693b5995578b99d7f2f171f1d96a 100644 (file)

--- a/src/include/replication/walreceiver.h

+++ b/src/include/replication/walreceiver.h

@@ -23,6 +23,7 @@

#include "utils/tuplestore.h"

/* user-settable parameters */

+extern bool wal_receiver_create_temp_slot;

extern int wal_receiver_status_interval;

extern int wal_receiver_timeout;

extern bool hot_standby_feedback;

@@ -121,6 +122,12 @@ typedef struct

char slotname[NAMEDATALEN];

+ /*

+ * If it's a temporary replication slot, it needs to be recreated when

+ * connecting.

+ */

+ bool is_temp_slot;

/* set true once conninfo is ready to display (obfuscated pwds etc) */

bool ready_to_display;

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