On Mon, Feb 17, 2020 at 04:57:04PM +0300, Sergei Kornilov wrote: > Thank you, here is updated patch
Thanks > I changed this comments because they describes behavior during > change value of wal_receiver_create_temp_slot. But yes, I need to > add some comments to RequestXLogStreaming. 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. >> As per the discussion done on this thread, let's also switch the >> parameter default to be disabled. > > Done (my vote is also for disabling this option by default). We visibly tend to move in this direction, at least based on our discussion. Let's see where this leads. For now, I have registered this patch to next CF (https://commitfest.postgresql.org/27/2456/), with yourself as author and myself as reviewer, and then let's wait for mainly Peter E. and others for more input. -- Michael
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);
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 3813eadfb4..e0f3ed5c2a 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -283,6 +283,7 @@ 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;
@@ -11901,7 +11902,7 @@ 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 2ab15c3cbb..ff45482faa 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
@@ -73,7 +79,6 @@
/* GUC variables */
-bool wal_receiver_create_temp_slot;
int wal_receiver_status_interval;
int wal_receiver_timeout;
bool hot_standby_feedback;
@@ -348,42 +353,23 @@ 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..821680a857 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';
+ /*
+ * 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)
+ {
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 8228e1f390..ec9cd3696c 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -2029,11 +2029,11 @@ 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 e1048c0047..1dd2a86567 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/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index c1128f89ec..683d87c491 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -4140,11 +4140,7 @@ 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>
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