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Subject: Re: Fix pg_stat_wal_receiver to show CONNECTING status
From: Chao Li <li.evan.chao@gmail.com>
In-Reply-To: <ag00OeH1sbt5ie_6@paquier.xyz>
Date: Wed, 20 May 2026 15:53:38 +0800
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>,
 Michael Paquier <michael.paquier@gmail.com>,
 Xuneng Zhou <xunengzhou@gmail.com>
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 <1F153E64-B791-42FA-A60A-64813B20B81E@gmail.com>
 <ag00OeH1sbt5ie_6@paquier.xyz>
To: Michael Paquier <michael@paquier.xyz>
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> On May 20, 2026, at 12:10, Michael Paquier <michael@paquier.xyz> =
wrote:
>=20
> On Wed, May 20, 2026 at 09:47:40AM +0800, Chao Li wrote:
>> I just read v2, and it is actually the first solution I tried. The
>> reason I gave up on that approach and switched to the implementation
>> in v1 is that it may wrongly report last_msg_send_time,
>> last_msg_receipt_time, and latest_end_time.
>=20
> As of the code, we have the following at the top of WalReceiverMain()
> before the first connection attempt:
>    /* Initialise to a sanish value */
>    now =3D GetCurrentTimestamp();
>    walrcv->lastMsgSendTime =3D
>       walrcv->lastMsgReceiptTime =3D walrcv->latestWalEndTime =3D now;
>=20

Was that okay because walrcv->ready_to_display was false, so the sane =
initial value would not show up through pg_stat_wal_receiver?

> And the state of v2 is actually fine, because we finish by reporting
> in the SQL calls values that represent the state the WAL receiver is=20=

> initialized at based on what the code does.  It would be IMO an issue
> to hide this information, as they can offer hits about the moment when
> we've begun a connection.
> --
> Michael

With v2, slot_name, sender_host, sender_port, and conninfo are already =
left NULL while the receiver is in CONNECTING state. I feel we don't =
have to show the timestamp fields either. Since the columns are named =
last_msg_send_time and last_msg_receipt_time, users may naturally =
interpret them as the last time a message was sent to or received from
the primary. If we show the standby server start time in those columns, =
I am afraid that could be confusing.

But I think it might be useful to show the *_lsn and *_tli values in =
CONNECTING state if they are available.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/