public inbox for [email protected]  

help / color / mirror / Atom feed

From: Robert Haas <[email protected]>
To: Fujii Masao <[email protected]>
Cc: Josh Berkus <[email protected]>
Cc: Kevin Grittner <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: Heikki Linnakangas <[email protected]>
Cc: [email protected]
Cc: PostgreSQL-development <[email protected]>
Subject: Re: [HACKERS] Streaming replication document improvements
Date: Tue, 20 Apr 2010 10:01:48 -0400
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>

On Tue, Apr 20, 2010 at 9:47 AM, Fujii Masao <[email protected]> wrote:
> Yeah, I agree with you, but the difference is only how to achieve.
> ISTM that there are three choices:
>
> 1. Heikki's proposal
>> ReservedBackends = superuser_reserved_connections + max_wal_senders
>> MaxBackends = max_connections + autovacuum_max_workers + max_wal_senders + 1

This seemed sensible to me when Heikki first described it, but now it
seems overly complex.

> 2. My proposal
>    Remove superuser privilege from replication connection

I'm not sure this really fixes the problem.  If we add a separate
replication privilege, then presumably superusers will automatically
have that privilege, in accord with our usual policy on such things.
So potentially someone could still set up replication using a
superuser account and then they could still get bitten by this
problem.

> 3. Your proposal
>    Treat superuser replication connection like non-superuser one

Well, only for this one very specific purpose.  I would adjust the
docs like this:

Determines the number of connection "slots" that are reserved for
connections by PostgreSQL  superusers. At most max_connections
connections can ever be active simultaneously. Whenever the number of
active concurrent connections is at least max_connections minus
superuser_reserved_connections, new connections will be accepted only
for superusers, and no new replication connections will be accepted.

I think that's pretty simple and clear.  If we want to burn an extra
sentence explaining what this is all about, we could add:

(If replication connections were permitted to use the reserved
connection slots, an installation with max_wal_senders set to a value
greater than or equal to the value set for
superuser_reserved_connections might find that no reserved connections
remained for interactive access to the database.)

> Since 3. is confusing for me, I like 1. or 2.

What do others think?

...Robert

view thread (34+ messages)  latest in thread

reply

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: [email protected]
  Cc: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]
  Subject: Re: [HACKERS] Streaming replication document improvements
  In-Reply-To: <[email protected]>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox