On Thu, Nov 2, 2023 at 7:19 AM Peter Smith <smithpb2...@gmail.com> wrote:
>
> But that's not quite compatible with what Alvaro [2] had written long
> back ("... the only acquisitions that would log messages are those in
> StartReplication and StartLogicalReplication.").
>
> In other words, ReplicationSlotAcquire/ReplicationSlotRelease is
> called by more places than you care to log from.
I refreshed my thoughts for this patch and I think it's enough if
walsenders alone log messages when slots become active and inactive.
How about something like the attached v11 patch?
--
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
From eed7c96d9cab98a576728792c2cb111ae61f930f Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Sat, 4 Nov 2023 21:59:27 +0000
Subject: [PATCH v11] Emit messages when replication slots become active and
inactive
These logs will be extremely useful on production servers to debug
and analyze inactive replication slot issues.
---
doc/src/sgml/config.sgml | 10 +++---
src/backend/replication/slot.c | 54 ++++++++++++++++++++++++++++-
src/backend/replication/walsender.c | 10 +++---
src/include/replication/slot.h | 2 ++
4 files changed, 65 insertions(+), 11 deletions(-)
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index bd70ff2e4b..6d14a94cf4 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -7510,11 +7510,11 @@ log_line_prefix = '%m [%p] %q%u@%d/%a '
</term>
<listitem>
<para>
- Causes each replication command to be logged in the server log.
- See <xref linkend="protocol-replication"/> for more information about
- replication command. The default value is <literal>off</literal>.
- Only superusers and users with the appropriate <literal>SET</literal>
- privilege can change this setting.
+ Causes each replication command and related activity to be logged in
+ the server log. See <xref linkend="protocol-replication"/> for more
+ information about replication command. The default value is
+ <literal>off</literal>. Only superusers and users with the appropriate
+ <literal>SET</literal> privilege can change this setting.
</para>
</listitem>
</varlistentry>
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index 99823df3c7..dfb564b04f 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -181,7 +181,12 @@ ReplicationSlotShmemExit(int code, Datum arg)
{
/* Make sure active replication slots are released */
if (MyReplicationSlot != NULL)
- ReplicationSlotRelease();
+ {
+ if (am_walsender)
+ ReplicationSlotReleaseAndLog();
+ else
+ ReplicationSlotRelease();
+ }
/* Also cleanup all the temporary slots. */
ReplicationSlotCleanup();
@@ -539,6 +544,26 @@ retry:
pgstat_acquire_replslot(s);
}
+/*
+ * A wrapper around ReplicationSlotAcquire() but logs a message when
+ * appropriate.
+ *
+ * This function is currently used only in walsender.
+ */
+void
+ReplicationSlotAcquireAndLog(const char *name, bool nowait)
+{
+ Assert(am_walsender);
+
+ ReplicationSlotAcquire(name, nowait);
+
+ ereport(log_replication_commands ? LOG : DEBUG1,
+ (errmsg("walsender process with PID %d acquired %s replication slot \"%s\"",
+ MyProcPid,
+ SlotIsPhysical(MyReplicationSlot) ? "physical" : "logical",
+ NameStr(MyReplicationSlot->data.name))));
+}
+
/*
* Release the replication slot that this backend considers to own.
*
@@ -598,6 +623,33 @@ ReplicationSlotRelease(void)
LWLockRelease(ProcArrayLock);
}
+/*
+ * A wrapper around ReplicationSlotAcquire() but logs a message when
+ * appropriate.
+ *
+ * This function is currently used only in walsender.
+ */
+void
+ReplicationSlotReleaseAndLog(void)
+{
+ char *slotname;
+ bool is_physical;
+
+ Assert(am_walsender);
+
+ slotname = pstrdup(NameStr(MyReplicationSlot->data.name));
+ is_physical = SlotIsPhysical(MyReplicationSlot);
+
+ ReplicationSlotRelease();
+
+ ereport(log_replication_commands ? LOG : DEBUG1,
+ (errmsg("walsender process with PID %d released %s replication slot \"%s\"",
+ MyProcPid,
+ is_physical ? "physical" : "logical", slotname)));
+
+ pfree(slotname);
+}
+
/*
* Cleanup all temporary slots created in current session.
*/
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index e250b0567e..2a1c5056c0 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -322,7 +322,7 @@ WalSndErrorCleanup(void)
wal_segment_close(xlogreader);
if (MyReplicationSlot != NULL)
- ReplicationSlotRelease();
+ ReplicationSlotReleaseAndLog();
ReplicationSlotCleanup();
@@ -697,7 +697,7 @@ StartReplication(StartReplicationCmd *cmd)
if (cmd->slotname)
{
- ReplicationSlotAcquire(cmd->slotname, true);
+ ReplicationSlotAcquireAndLog(cmd->slotname, true);
if (SlotIsLogical(MyReplicationSlot))
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
@@ -843,7 +843,7 @@ StartReplication(StartReplicationCmd *cmd)
}
if (cmd->slotname)
- ReplicationSlotRelease();
+ ReplicationSlotReleaseAndLog();
/*
* Copy is finished now. Send a single-row result set indicating the next
@@ -1261,7 +1261,7 @@ StartLogicalReplication(StartReplicationCmd *cmd)
Assert(!MyReplicationSlot);
- ReplicationSlotAcquire(cmd->slotname, true);
+ ReplicationSlotAcquireAndLog(cmd->slotname, true);
/*
* Force a disconnect, so that the decoding code doesn't need to care
@@ -1323,7 +1323,7 @@ StartLogicalReplication(StartReplicationCmd *cmd)
WalSndLoop(XLogSendLogical);
FreeDecodingContext(logical_decoding_ctx);
- ReplicationSlotRelease();
+ ReplicationSlotReleaseAndLog();
replication_active = false;
if (got_STOPPING)
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index d3535eed58..3dc8699106 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -223,7 +223,9 @@ extern void ReplicationSlotPersist(void);
extern void ReplicationSlotDrop(const char *name, bool nowait);
extern void ReplicationSlotAcquire(const char *name, bool nowait);
+extern void ReplicationSlotAcquireAndLog(const char *name, bool nowait);
extern void ReplicationSlotRelease(void);
+extern void ReplicationSlotReleaseAndLog(void);
extern void ReplicationSlotCleanup(void);
extern void ReplicationSlotSave(void);
extern void ReplicationSlotMarkDirty(void);
--
2.34.1
