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From: Ramakrishna m <ram.pgdb@gmail.com>
Date: Tue, 23 Apr 2024 22:55:40 +0530
Message-ID: <CAG-eXHLx3JGO+pGVBRDPvpUamc6Jbutj2egH7Y8+XTgZzy0V7A@mail.gmail.com>
Subject: Logical Replication Delay on Remote Server
To: pgsql-general@lists.postgresql.org
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Hi Team,

I am facing replication lag in postgres16 at times,not able to find the
reason.

Please find the configuration:
1) Two replication slots for two servers (1 is the same data center,
another remote)
2) weekly once/twice facing lag(around 2GB for 1k TPS environment) in the
remote   replication slot and another same data center server slot with 0
lag.

My observation:

1) Noticed pg_stat_replication_slot total_txn reduced from 1k to 5 or 6 but
other  slot is same with 1k TPS
2)And noticed lag for remote slot but fine with same data center
3) Most importantly I have plenty of Bandwidth available in n/w ,2GB is
still freely available out of 4GB network.
4)No IO issues on servers
I am not able to prove if this is due to Network .Can you help me how to
proceed on this?
At Least how the logical decoding total_txn is counting the view
pg_stat_replication_slot?

-- 
Thanks & Regards,
Ram.

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<div dir=3D"ltr"><div><div><font face=3D"arial, sans-serif">Hi Team,<br></f=
ont></div><div><font face=3D"arial, sans-serif"><br></font></div><div><font=
 face=3D"arial, sans-serif">I am facing=C2=A0<span class=3D"gmail-il">repli=
cation</span>=C2=A0lag in postgres16 at times,not able to find the reason.<=
/font></div><div><font face=3D"arial, sans-serif"><br>Please find the confi=
guration:<br>1) Two=C2=A0<span class=3D"gmail-il">replication</span>=C2=A0s=
lots for two servers (1 is the same data center, another=C2=A0<span class=
=3D"gmail-il">remote</span>)</font></div><div><font face=3D"arial, sans-ser=
if">2) weekly once/twice facing lag(around 2GB for 1k TPS environment) in t=
he=C2=A0<span class=3D"gmail-il">remote</span>=C2=A0 =C2=A0<span class=3D"g=
mail-il">replication</span>=C2=A0slot and another same data center=C2=A0<sp=
an class=3D"gmail-il">server</span>=C2=A0slot with 0 lag.<br><br></font></d=
iv><div><font face=3D"arial, sans-serif">My observation:</font></div><div><=
font face=3D"arial, sans-serif"><br>1) Noticed pg_stat_replication_slot=C2=
=A0total_txn reduced from 1k to 5 or 6 but other=C2=A0 slot is same with 1k=
 TPS<br>2)And noticed lag for=C2=A0<span class=3D"gmail-il">remote</span>=
=C2=A0slot but fine with same data center<br>3) Most importantly=C2=A0I hav=
e plenty of Bandwidth available in n/w ,2GB is still freely available=C2=A0=
out of 4GB network.<br>4)No IO issues on servers<br>I am not able to prove =
if this is due to Network .Can you help me how to proceed on this?=C2=A0<br=
>At Least=C2=A0how the=C2=A0<span class=3D"gmail-il">logical</span>=C2=A0de=
coding=C2=A0total_txn is counting the view pg_stat_replication_slot?<font c=
olor=3D"#888888"><br></font></font></div><font color=3D"#888888"><br class=
=3D"gmail-Apple-interchange-newline"></font></div><span class=3D"gmail_sign=
ature_prefix">-- </span><br><div dir=3D"ltr" class=3D"gmail_signature" data=
-smartmail=3D"gmail_signature"><div dir=3D"ltr">Thanks &amp; Regards,<div>R=
am.<br></div></div></div></div>

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