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From: Bharath Rupireddy <[email protected]>
To: Alvaro Herrera <[email protected]>
Cc: Amit Kapila <[email protected]>
Cc: Kyotaro Horiguchi <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: add log messages when replication slots become active and inactive (was Re: Is it worth adding ReplicationSlot active_pid to ReplicationSlotPersistentData?)
Date: Thu, 23 Mar 2023 23:03:38 +0530
Message-ID: <CALj2ACXvqFcxro64q4gjDeBNLgyPH0E6bG-WJ6w7qBqbggj3=w@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <CAA4eK1+CoHVhP6hs+5-_1_A9EymSyqDPzHxBs1jSrTm5fj6CvQ@mail.gmail.com>
	<[email protected]>

On Thu, Mar 23, 2023 at 3:37 PM Alvaro Herrera <[email protected]> wrote:
>
> On 2023-Mar-22, Amit Kapila wrote:
>
> > I see that you have modified the patch to address the comments from
> > Alvaro. Personally, I feel it would be better to add such a message at
> > a centralized location instead of spreading these in different callers
> > of slot acquire/release functionality to avoid getting these missed in
> > the new callers in the future. However, if Alvaro and others think
> > that the current style is better then we should go ahead and do it
> > that way. I hope that we should be able to decide on this and get it
> > into PG16. Anyone else would like to weigh in here?
>
> I like Peter Smith's suggestion downthread.

+1. Please review the attached v8 patch further.

-- 
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com


Attachments:

  [application/octet-stream] v8-0001-Add-LOG-messages-when-replication-slots-become-ac.patch (6.4K, ../CALj2ACXvqFcxro64q4gjDeBNLgyPH0E6bG-WJ6w7qBqbggj3=w@mail.gmail.com/2-v8-0001-Add-LOG-messages-when-replication-slots-become-ac.patch)
  download | inline diff:
From b0824cbe21d02d6826aead6cc7cf50c955160626 Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <[email protected]>
Date: Thu, 23 Mar 2023 17:21:12 +0000
Subject: [PATCH v8] Add LOG 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            |  7 +++--
 src/backend/replication/slot.c      | 45 +++++++++++++++++++++++++++++
 src/backend/replication/walsender.c | 17 +++++++++++
 src/backend/utils/misc/guc_tables.c |  2 +-
 src/include/replication/slot.h      |  2 ++
 5 files changed, 69 insertions(+), 4 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 481f93cea1..f9b0d3c9a9 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -7593,9 +7593,10 @@ 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>.
+        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>
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index 2293c0c6fc..4dba028ab9 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -180,7 +180,16 @@ ReplicationSlotShmemExit(int code, Datum arg)
 {
 	/* Make sure active replication slots are released */
 	if (MyReplicationSlot != NULL)
+	{
+		bool is_physical;
+		char *slotname;
+
+		is_physical = SlotIsPhysical(MyReplicationSlot);
+		slotname = pstrdup(NameStr(MyReplicationSlot->data.name));
 		ReplicationSlotRelease();
+		LogReplicationSlotReleased(is_physical, slotname);
+		pfree(slotname);
+	}
 
 	/* Also cleanup all the temporary slots. */
 	ReplicationSlotCleanup();
@@ -596,6 +605,42 @@ ReplicationSlotRelease(void)
 	LWLockRelease(ProcArrayLock);
 }
 
+/*
+ * Helper function to log a message after replication slot acquisition.
+ */
+void
+LogReplicationSlotAquired(bool is_physical, char *slotname)
+{
+	Assert(MyReplicationSlot != NULL);
+
+	if (is_physical)
+		ereport(log_replication_commands ? LOG : DEBUG3,
+				(errmsg("acquired physical replication slot \"%s\"",
+						slotname)));
+	else
+		ereport(log_replication_commands ? LOG : DEBUG3,
+				(errmsg("acquired logical replication slot \"%s\"",
+						slotname)));
+}
+
+/*
+ * Helper function to log a message after replication slot release.
+ */
+void
+LogReplicationSlotReleased(bool is_physical, char *slotname)
+{
+	Assert(MyReplicationSlot == NULL);
+
+	if (is_physical)
+		ereport(log_replication_commands ? LOG : DEBUG3,
+				(errmsg("released physical replication slot \"%s\"",
+						slotname)));
+	else
+		ereport(log_replication_commands ? LOG : DEBUG3,
+				(errmsg("released logical replication slot \"%s\"",
+						slotname)));
+}
+
 /*
  * Cleanup all temporary slots created in current session.
  */
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 75e8363e24..38d25ed3c8 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -322,7 +322,16 @@ WalSndErrorCleanup(void)
 		wal_segment_close(xlogreader);
 
 	if (MyReplicationSlot != NULL)
+	{
+		bool is_physical;
+		char *slotname;
+
+		is_physical = SlotIsPhysical(MyReplicationSlot);
+		slotname = pstrdup(NameStr(MyReplicationSlot->data.name));
 		ReplicationSlotRelease();
+		LogReplicationSlotReleased(is_physical, slotname);
+		pfree(slotname);
+	}
 
 	ReplicationSlotCleanup();
 
@@ -703,6 +712,8 @@ StartReplication(StartReplicationCmd *cmd)
 					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 					 errmsg("cannot use a logical replication slot for physical replication")));
 
+		LogReplicationSlotAquired(true, cmd->slotname);
+
 		/*
 		 * We don't need to verify the slot's restart_lsn here; instead we
 		 * rely on the caller requesting the starting point to use.  If the
@@ -843,7 +854,10 @@ StartReplication(StartReplicationCmd *cmd)
 	}
 
 	if (cmd->slotname)
+	{
 		ReplicationSlotRelease();
+		LogReplicationSlotReleased(true, cmd->slotname);
+	}
 
 	/*
 	 * Copy is finished now. Send a single-row result set indicating the next
@@ -1260,6 +1274,8 @@ StartLogicalReplication(StartReplicationCmd *cmd)
 						cmd->slotname),
 				 errdetail("This slot has been invalidated because it exceeded the maximum reserved size.")));
 
+	LogReplicationSlotAquired(false, cmd->slotname);
+
 	/*
 	 * Force a disconnect, so that the decoding code doesn't need to care
 	 * about an eventual switch from running in recovery, to running in a
@@ -1321,6 +1337,7 @@ StartLogicalReplication(StartReplicationCmd *cmd)
 
 	FreeDecodingContext(logical_decoding_ctx);
 	ReplicationSlotRelease();
+	LogReplicationSlotReleased(false, cmd->slotname);
 
 	replication_active = false;
 	if (got_STOPPING)
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index 1c0583fe26..ea41ccc7e2 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -1203,7 +1203,7 @@ struct config_bool ConfigureNamesBool[] =
 	},
 	{
 		{"log_replication_commands", PGC_SUSET, LOGGING_WHAT,
-			gettext_noop("Logs each replication command."),
+			gettext_noop("Logs each replication command and related activity."),
 			NULL
 		},
 		&log_replication_commands,
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index 8872c80cdf..147e4d4371 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -202,6 +202,8 @@ extern void ReplicationSlotDrop(const char *name, bool nowait);
 
 extern void ReplicationSlotAcquire(const char *name, bool nowait);
 extern void ReplicationSlotRelease(void);
+extern void LogReplicationSlotAquired(bool is_physical, char *slotname);
+extern void LogReplicationSlotReleased(bool is_physical, char *slotname);
 extern void ReplicationSlotCleanup(void);
 extern void ReplicationSlotSave(void);
 extern void ReplicationSlotMarkDirty(void);
-- 
2.34.1



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  Subject: Re: add log messages when replication slots become active and inactive (was Re: Is it worth adding ReplicationSlot active_pid to ReplicationSlotPersistentData?)
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