On Thu, May 5, 2022 at 2:57 PM Bharath Rupireddy
<bharath.rupireddyforpostg...@gmail.com> wrote:
>
> On Fri, Apr 29, 2022 at 4:02 PM Alvaro Herrera <alvhe...@alvh.no-ip.org>
> wrote:
> >
> > If I read the code right, this patch emits logs when
> > pg_logical_slot_get_changes and pg_replication_slot_advance SQL
> > functions are called. Is this desirable/useful, for the use case you
> > stated at start of thread? I think it is most likely pointless. If you
> > get rid of those, then the only acquisitions that would log messages are
> > those in StartReplication and StartLogicalReplication. So I wonder if
> > it would be better to leave the API of ReplicationSlotAcquire() alone,
> > and instead make StartReplication and StartLogicalReplication
> > responsible for those messages.
> >
> > I didn't look at the release-side messages you're adding, but I suppose
> > it should be symmetrical.
Here's the v6 patch, a much simpler one - no changes to any of the
existing function APIs. Please see the sample logs at [1]. There's a
bit of duplicate code in the v6 patch, if the overall approach looks
okay, I can remove that too in the next version of the patch.
Thoughts?
[1]
2022-07-25 12:30:14.847 UTC [152873] LOG: acquired physical
replication slot "foo"
2022-07-25 12:30:20.878 UTC [152873] LOG: released physical
replication slot "foo"
2022-07-25 12:49:18.023 UTC [168738] LOG: acquired logical
replication slot "bar"
2022-07-25 12:49:28.105 UTC [168738] LOG: released logical
replication slot "bar"
Regards,
Bharath Rupireddy.
From c57cfd8dd27eaf9e0c17c47769cb24b8ab961116 Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Mon, 25 Jul 2022 12:51:26 +0000
Subject: [PATCH v6] 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 | 21 ++++++++++++++++
src/backend/replication/walsender.c | 39 +++++++++++++++++++++++++++++
3 files changed, 64 insertions(+), 3 deletions(-)
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index e2d728e0c4..8bf3c2ab53 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -7461,9 +7461,10 @@ 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 850b74936f..43563bec7e 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -179,8 +179,29 @@ ReplicationSlotShmemExit(int code, Datum arg)
{
/* Make sure active replication slots are released */
if (MyReplicationSlot != NULL)
+ {
+ bool is_physical;
+ char slotname[NAMEDATALEN] = {0};
+
+ is_physical = SlotIsPhysical(MyReplicationSlot);
+ strcpy(slotname, NameStr(MyReplicationSlot->data.name));
+
ReplicationSlotRelease();
+ 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)));
+ }
+ }
+
/* Also cleanup all the temporary slots. */
ReplicationSlotCleanup();
}
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 3a86786cc3..ebd34316e2 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -322,8 +322,29 @@ WalSndErrorCleanup(void)
wal_segment_close(xlogreader);
if (MyReplicationSlot != NULL)
+ {
+ bool is_physical;
+ char slotname[NAMEDATALEN] = {0};
+
+ is_physical = SlotIsPhysical(MyReplicationSlot);
+ strcpy(slotname, NameStr(MyReplicationSlot->data.name));
+
ReplicationSlotRelease();
+ 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)));
+ }
+ }
+
ReplicationSlotCleanup();
replication_active = false;
@@ -704,6 +725,10 @@ StartReplication(StartReplicationCmd *cmd)
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("cannot use a logical replication slot for physical replication")));
+ ereport(log_replication_commands ? LOG : DEBUG3,
+ (errmsg("acquired physical replication slot \"%s\"",
+ 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
@@ -844,8 +869,14 @@ StartReplication(StartReplicationCmd *cmd)
}
if (cmd->slotname)
+ {
ReplicationSlotRelease();
+ ereport(log_replication_commands ? LOG : DEBUG3,
+ (errmsg("released physical replication slot \"%s\"",
+ cmd->slotname)));
+ }
+
/*
* Copy is finished now. Send a single-row result set indicating the next
* timeline.
@@ -1256,6 +1287,10 @@ StartLogicalReplication(StartReplicationCmd *cmd)
cmd->slotname),
errdetail("This slot has been invalidated because it exceeded the maximum reserved size.")));
+ ereport(log_replication_commands ? LOG : DEBUG3,
+ (errmsg("acquired logical replication slot \"%s\"",
+ 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
@@ -1318,6 +1353,10 @@ StartLogicalReplication(StartReplicationCmd *cmd)
FreeDecodingContext(logical_decoding_ctx);
ReplicationSlotRelease();
+ ereport(log_replication_commands ? LOG : DEBUG3,
+ (errmsg("released logical replication slot \"%s\"",
+ cmd->slotname)));
+
replication_active = false;
if (got_STOPPING)
proc_exit(0);
--
2.34.1
