Re: Patch for reserved connections for replication users - Mailing list pgsql-hackers

From Euler Taveira
Subject Re: Patch for reserved connections for replication users
Date
Msg-id 5263E472.2030606@timbira.com.br
Whole thread Raw
In response to Re: Patch for reserved connections for replication users  (Josh Berkus <josh@agliodbs.com>)
List pgsql-hackers
On 15-10-2013 14:34, Josh Berkus wrote:
> On 10/15/2013 07:36 AM, Robert Haas wrote:
>> On Tue, Oct 15, 2013 at 10:34 AM, Andres Freund <andres@2ndquadrant.com> wrote:
>>> Josh said we should treat replication connections in a separate "pool"
>>> from normal database connections, right? So you withdraw your earlier
>>> objection to that?
>>
>> I don't think that's what he said.  Here's what I was referring to:
> 
> To clarify: I do, indeed, support the idea of treating replication
> connections as a pool outside of max_connections.  Here's why:
> 
+1. I've already faced the same problem Josh described. Even if it is
documented (as in max_wal_senders), it is not easy to figure out why you
can't connect (check 2 parameters and query 2 views). Also, the 'check
connections' task is so complicated in a monitoring tool.

Let's separate the replication connections in another pool (that is not
related to user connections). We already have the infrastructure to
limit replication connections (max_wal_senders), let's use it.

> FATAL: connection limit exceeded for non-superusers
> 
> SHOW max_connections;
> 
> 100
> 
> SELECT COUNT(*) FROM pg_stat_activity;
> 
> 94
> 
> SHOW superuser_reserved_connections;
> 
> 3
> 
> ????
> 
> ... search around quite a bit,  eventually figure out that you have
> three replication connections open.  We've already set up an illogical
> and hard-to-troubleshoot situation where replication connections do not
> appear in pg_stat_activity, yet they are counted against max_connections.
> 
Another situation is when you can't run pg_basebackup because automated
routines got all of the available connections and the replication user
is not a superuser (even if replication user is a superuser, if some app
run as superuser there won't be slots available).


--   Euler Taveira                   Timbira - http://www.timbira.com.br/  PostgreSQL: Consultoria, Desenvolvimento,
Suporte24x7 e Treinamento
 



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