Feedback-ID: i0c21471d:Fastmail
User-Agent: Cyrus-JMAP/3.9.0-alpha0-647-g545049cfe6-fm-20230814.001-g545049cf
Mime-Version: 1.0
Message-Id: <b151f622-86c4-429e-8629-e48b7038c6c1@app.fastmail.com>
In-Reply-To: <169279891191.621.15758133625753505628@wrigleys.postgresql.org>
References: <169279891191.621.15758133625753505628@wrigleys.postgresql.org>
Date: Wed, 23 Aug 2023 15:31:04 -0300
From: "Euler Taveira" <euler@eulerto.com>
To: "yanliang lei" <msdnchina@163.com>, pgsql-docs@lists.postgresql.org
Subject: Re: There is no description about "Logical Replication also use or
 occupy
 max_wal_senders ",
Content-Type: multipart/alternative;
 boundary=1fa6bbecf7994409a2d3be490c186a2f
Archived-At: 
 <https://www.postgresql.org/message-id/b151f622-86c4-429e-8629-e48b7038c6c1%40app.fastmail.com>
Precedence: bulk

--1fa6bbecf7994409a2d3be490c186a2f
Content-Type: text/plain;charset=utf-8
Content-Transfer-Encoding: quoted-printable

On Wed, Aug 23, 2023, at 10:55 AM, PG Doc comments form wrote:
> max_wal_senders (integer)
>=20
> Specifies the maximum number of concurrent connections from standby se=
rvers
> or streaming base backup clients (i.e., the maximum number of simultan=
eously
> running WAL sender processes). The default is 10. The value 0 means
> replication is disabled. Abrupt disconnection of a streaming client mi=
ght
> leave an orphaned connection slot behind until a timeout is reached, s=
o this
> parameter should be set slightly higher than the maximum number of exp=
ected
> clients so disconnected clients can immediately reconnect. This parame=
ter
> can only be set at server start. Also, wal_level must be set to replic=
a or
> higher to allow connections from standby servers.
>=20
> When running a standby server, you must set this parameter to the same=
 or
> higher value than on the primary server. Otherwise, queries will not be
> allowed in the standby server.
>=20
>=20
>=20
> In the above description=EF=BC=8C there is no description about "Logic=
al Replication
> also use or occupy  max_wal_senders ",

According to the glossary [1], standby server (referred as "replica") is

Replica (server)
A database that is paired with a primary database and is maintaining a c=
opy of
some or all of the primary database's data. The foremost reasons for doi=
ng this
are to allow for greater access to that data, and to maintain availabili=
ty of
the data in the event that the primary becomes unavailable.

... and it implies both (logical and physical) replicas. The logical
replication [2] setup also informs that you need to adjust max_wal_sende=
rs.

Maybe the "standby" terminology could be expanded to avoid confusion for=
 users
from other technologies. If I were to suggest a modification, it would b=
e in
the first paragraph in the "Replication" section [3] (something like "Pr=
imaries
can send data, while standbys are always receivers of physically or logi=
cally
replicated data") or even better rephrase the "Replica (server)" term in=
 the
glossary [1].

> so, I suggest the following modification:
> Specifies the maximum number of concurrent connections from standby se=
rvers
> or streaming base backup clients  and  Logical Replication (i.e., the
> maximum number of simultaneously running WAL sender processes).  ---pl=
ease
> note ,"and  Logical Replication" is newly added=E3=80=82
>=20

The logical replication feature wasn't newly added. It was added almost =
6 years
ago and version 10 (that adds it) was EOL more than 9 months ago.


[1] https://www.postgresql.org/docs/current/glossary.html
[2] https://www.postgresql.org/docs/current/logical-replication-config.h=
tml
[3] https://www.postgresql.org/docs/current/runtime-config-replication.h=
tml


--
Euler Taveira
EDB   https://www.enterprisedb.com/

--1fa6bbecf7994409a2d3be490c186a2f
Content-Type: text/html;charset=utf-8
Content-Transfer-Encoding: quoted-printable

<!DOCTYPE html><html><head><title></title><style type=3D"text/css">p.Mso=
Normal,p.MsoNoSpacing{margin:0}</style></head><body><div>On Wed, Aug 23,=
 2023, at 10:55 AM, PG Doc comments form wrote:<br></div><blockquote typ=
e=3D"cite" id=3D"qt" style=3D""><div>max_wal_senders (integer)<br></div>=
<div><br></div><div>Specifies the maximum number of concurrent connectio=
ns from standby servers<br></div><div>or streaming base backup clients (=
i.e., the maximum number of simultaneously<br></div><div>running WAL sen=
der processes). The default is 10. The value 0 means<br></div><div>repli=
cation is disabled. Abrupt disconnection of a streaming client might<br>=
</div><div>leave an orphaned connection slot behind until a timeout is r=
eached, so this<br></div><div>parameter should be set slightly higher th=
an the maximum number of expected<br></div><div>clients so disconnected =
clients can immediately reconnect. This parameter<br></div><div>can only=
 be set at server start. Also, wal_level must be set to replica or<br></=
div><div>higher to allow connections from standby servers.<br></div><div=
><br></div><div>When running a standby server, you must set this paramet=
er to the same or<br></div><div>higher value than on the primary server.=
 Otherwise, queries will not be<br></div><div>allowed in the standby ser=
ver.<br></div><div><br></div><div><br></div><div><br></div><div>In the a=
bove description=EF=BC=8C there is no description about "Logical Replica=
tion<br></div><div>also use or occupy&nbsp; max_wal_senders ",<br></div>=
</blockquote><div><br></div><div>According to the glossary [1], standby =
server (referred as "replica") is<br></div><div><br></div><div>Replica (=
server)<br></div><div>A database that is paired with a primary database =
and is maintaining a copy of<br></div><div>some or all of the primary da=
tabase's data. The foremost reasons for doing this<br></div><div>are to =
allow for greater access to that data, and to maintain availability of<b=
r></div><div>the data in the event that the primary becomes unavailable.=
<br></div><div><br></div><div>... and it implies both (logical and physi=
cal) replicas. The logical<br></div><div>replication [2] setup also info=
rms that you need to adjust max_wal_senders.<br></div><div><br></div><di=
v>Maybe the "standby" terminology could be expanded to avoid confusion f=
or users<br></div><div>from other technologies. If I were to suggest a m=
odification, it would be in<br></div><div>the first paragraph in the "Re=
plication" section [3] (something like "Primaries<br></div><div>can send=
 data, while standbys are always receivers of physically or logically<br=
></div><div>replicated data") or even better rephrase the "Replica (serv=
er)" term in the<br></div><div>glossary [1].<br></div><div><br></div><bl=
ockquote type=3D"cite" id=3D"qt" style=3D""><div>so, I suggest the follo=
wing modification:<br></div><div>Specifies the maximum number of concurr=
ent connections from standby servers<br></div><div>or streaming base bac=
kup clients&nbsp; and&nbsp; Logical Replication (i.e., the<br></div><div=
>maximum number of simultaneously running WAL sender processes).&nbsp; -=
--please<br></div><div>note ,"and&nbsp; Logical Replication" is newly ad=
ded=E3=80=82<br></div><div><br></div></blockquote><div><br></div><div>Th=
e logical replication feature wasn't newly added. It was added almost 6 =
years<br></div><div>ago and version 10 (that adds it) was EOL more than =
9 months ago.<br></div><div><br></div><div><br></div><div>[1] <a href=3D=
"https://www.postgresql.org/docs/current/glossary.html">https://www.post=
gresql.org/docs/current/glossary.html</a><br></div><div>[2] <a href=3D"h=
ttps://www.postgresql.org/docs/current/logical-replication-config.html">=
https://www.postgresql.org/docs/current/logical-replication-config.html<=
/a><br></div><div>[3] <a href=3D"https://www.postgresql.org/docs/current=
/runtime-config-replication.html">https://www.postgresql.org/docs/curren=
t/runtime-config-replication.html</a><br></div><div><br></div><div><br><=
/div><div id=3D"sig112409080"><div class=3D"signature">--<br></div><div =
class=3D"signature">Euler Taveira<br></div><div class=3D"signature">EDB&=
nbsp;&nbsp; <a href=3D"https://www.enterprisedb.com/">https://www.enterp=
risedb.com/</a><br></div></div><div><br></div></body></html>
--1fa6bbecf7994409a2d3be490c186a2f--