Hello
> I have reworked that part, adding more comments about the use of GUC
> parameters when establishing the connection to the primary for a WAL
> receiver. And also I have added an extra comment to walreceiver.c
> about the use of GUcs in general, to avoid this stuff again in the
> future. There were some extra nits with the format of
> postgresql.conf.sample.
Thank you! I just noticed that you removed my proposed change to this condition
in RequestXLogStreaming
- if (slotname != NULL)
+ if (slotname != NULL && slotname[0] != '\0')
We need this change to set is_temp_slot properly. PrimarySlotName GUC can
usually be an empty string, so just "slotname != NULL" is not enough.
I attached patch with this change.
regards, Sergei
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 672bf6f1ee..8b742c83c5 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -4160,11 +4160,7 @@ ANY <replaceable class="parameter">num_sync</replaceable> ( <replaceable class="
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.
+ The default is off. This parameter can only be set at server start.
</para>
</listitem>
</varlistentry>
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index de2d4ee582..483fedb218 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -284,6 +284,7 @@ bool StandbyModeRequested = false;
char *PrimaryConnInfo = NULL;
char *PrimarySlotName = NULL;
char *PromoteTriggerFile = NULL;
+bool wal_receiver_create_temp_slot = false;
/* are we currently in standby mode? */
bool StandbyMode = false;
@@ -11951,7 +11952,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
}
curFileTLI = tli;
RequestXLogStreaming(tli, ptr, PrimaryConnInfo,
- PrimarySlotName);
+ PrimarySlotName, wal_receiver_create_temp_slot);
receivedUpto = 0;
}
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index 25e0333c9e..779d19f1c1 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -15,6 +15,12 @@
* WalRcv->receivedUpto variable in shared memory, to inform the startup
* process of how far it can proceed with XLOG replay.
*
+ * WAL receivers cannot load directly GUC parameters used when establishing
+ * their connection to the primary, and rely on parameter values passed down
+ * by the startup process when WAL streaming is requested. This applies
+ * to for example the replication slot creation and the connection string to
+ * use for the connection with the primary.
+ *
* If the primary server ends streaming, but doesn't disconnect, walreceiver
* goes into "waiting" mode, and waits for the startup process to give new
* instructions. The startup process will treat that the same as
@@ -74,7 +80,6 @@
/* GUC variables */
-bool wal_receiver_create_temp_slot;
int wal_receiver_status_interval;
int wal_receiver_timeout;
bool hot_standby_feedback;
@@ -349,42 +354,23 @@ 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
+ * Create temporary replication slot if requested. In that
+ * case, we update 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' || is_temp_slot)
+ if (is_temp_slot)
{
- bool changed = false;
+ snprintf(slotname, sizeof(slotname),
+ "pg_walreceiver_%lld",
+ (long long int) walrcv_get_backend_pid(wrconn));
- if (wal_receiver_create_temp_slot)
- {
- snprintf(slotname, sizeof(slotname),
- "pg_walreceiver_%lld",
- (long long int) walrcv_get_backend_pid(wrconn));
+ walrcv_create_slot(wrconn, slotname, true, 0, NULL);
- walrcv_create_slot(wrconn, slotname, true, 0, NULL);
- changed = true;
- }
- else if (slotname[0] != '\0')
- {
- slotname[0] = '\0';
- changed = true;
- }
-
- if (changed)
- {
- SpinLockAcquire(&walrcv->mutex);
- strlcpy(walrcv->slotname, slotname, NAMEDATALEN);
- walrcv->is_temp_slot = wal_receiver_create_temp_slot;
- SpinLockRelease(&walrcv->mutex);
- }
+ SpinLockAcquire(&walrcv->mutex);
+ strlcpy(walrcv->slotname, slotname, NAMEDATALEN);
+ SpinLockRelease(&walrcv->mutex);
}
/*
diff --git a/src/backend/replication/walreceiverfuncs.c b/src/backend/replication/walreceiverfuncs.c
index 89c903e45a..21d1823607 100644
--- a/src/backend/replication/walreceiverfuncs.c
+++ b/src/backend/replication/walreceiverfuncs.c
@@ -215,13 +215,19 @@ ShutdownWalRcv(void)
/*
* Request postmaster to start walreceiver.
*
- * recptr indicates the position where streaming should begin, conninfo
- * is a libpq connection string to use, and slotname is, optionally, the name
- * of a replication slot to acquire.
+ * "recptr" indicates the position where streaming should begin. "conninfo"
+ * is a libpq connection string to use. "slotname" is, optionally, the name
+ * of a replication slot to acquire. "create_temp_slot" indicates to create
+ * a temporary slot when no "slotname" is given.
+ *
+ * WAL receivers do not directly load GUC parameters used for the connection
+ * to the primary, and rely on the values passed down by the caller of this
+ * routine instead. Hence, the addition of any new parameters should happen
+ * through this code path.
*/
void
RequestXLogStreaming(TimeLineID tli, XLogRecPtr recptr, const char *conninfo,
- const char *slotname)
+ const char *slotname, bool create_temp_slot)
{
WalRcvData *walrcv = WalRcv;
bool launch = false;
@@ -248,10 +254,22 @@ RequestXLogStreaming(TimeLineID tli, XLogRecPtr recptr, const char *conninfo,
else
walrcv->conninfo[0] = '\0';
- if (slotname != NULL)
+ /*
+ * Use configured replication slot if present, and ignore the value
+ * of create_temp_slot as the slot name should be persistent. Otherwise,
+ * use create_temp_slot to determine whether this WAL receiver should
+ * create a temporary slot by itself and use it, or not.
+ */
+ if (slotname != NULL && slotname[0] != '\0')
+ {
strlcpy((char *) walrcv->slotname, slotname, NAMEDATALEN);
+ walrcv->is_temp_slot = false;
+ }
else
+ {
walrcv->slotname[0] = '\0';
+ walrcv->is_temp_slot = create_temp_slot;
+ }
if (walrcv->walRcvState == WALRCV_STOPPED)
{
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 68082315ac..80b6801c82 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -2030,11 +2030,11 @@ static struct config_bool ConfigureNamesBool[] =
},
{
- {"wal_receiver_create_temp_slot", PGC_SIGHUP, REPLICATION_STANDBY,
+ {"wal_receiver_create_temp_slot", PGC_POSTMASTER, 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,
+ false,
NULL, NULL, NULL
},
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index aa44f0c9bf..f2e55d1bd3 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -321,7 +321,9 @@
#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_create_temp_slot = off # Create temp slot if primary_slot_name
+ # is not set.
+ # (change requires restart)
#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/access/xlog.h b/src/include/access/xlog.h
index 98b033fc20..12362421d7 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -129,6 +129,7 @@ extern int recoveryTargetAction;
extern int recovery_min_apply_delay;
extern char *PrimaryConnInfo;
extern char *PrimarySlotName;
+extern bool wal_receiver_create_temp_slot;
/* indirectly set via GUC system */
extern TransactionId recoveryTargetXid;
diff --git a/src/include/replication/walreceiver.h b/src/include/replication/walreceiver.h
index e08afc6548..cf3e43128c 100644
--- a/src/include/replication/walreceiver.h
+++ b/src/include/replication/walreceiver.h
@@ -23,7 +23,6 @@
#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;
@@ -321,7 +320,8 @@ extern void ShutdownWalRcv(void);
extern bool WalRcvStreaming(void);
extern bool WalRcvRunning(void);
extern void RequestXLogStreaming(TimeLineID tli, XLogRecPtr recptr,
- const char *conninfo, const char *slotname);
+ const char *conninfo, const char *slotname,
+ bool create_temp_slot);
extern XLogRecPtr GetWalRcvWriteRecPtr(XLogRecPtr *latestChunkStart, TimeLineID *receiveTLI);
extern int GetReplicationApplyDelay(void);
extern int GetReplicationTransferLatency(void);
