Re: max_wal_senders must die

On Tue, Oct 19, 2010 at 13:14, Stefan Kaltenbrunner
<stefan(at)kaltenbrunner(dot)cc> wrote:
> Josh Berkus wrote:
>>
>> Hackers,
>>
>> What purpose is served, exactly, by max_wal_senders?
>>
>> In order for a standby to connect, it must have a superuser login, and
>> replication connections must be enabled in pg_hba.conf.  How is having one
>> more setting in one more file you have to enable on the master benefitting
>> anyone?
>>
>> Under what bizarre set of circumstances would anyone have runaway
>> connections from replicas to the master?
>>
>> Proposed that we simply remove this setting in 9.1.  The real maximum wal
>> senders should be whatever max_connections is.
>
> I disagree - limiting the maximum number of replication connections is
> important for my usecases.
> Replication connections are significantly more heavilyweight than a normal
> connection and right now I for example simply use this setting to prevent
> stupid mistakes (especially in virtualized^cloudstyle environments).
>
> What we really should look into is using a less privileged role - or
> dedicated replication role - and use the existing per role connection limit
> feature. That  feature is unlimited by default, people can change it like
> for every role and we can git rid of that guc.

+1 for being able to control it that wya - that should keep it simple
for the newbie usecase, while retaining the ability for fine-grained
control for those who need it.

I think it's already on the TODO for 9.1 to use a separate role for it...

If we want something fixed *now*, should we perhaps just bump the
*default* value for max_wal_senders to 5 or something?

--
 Magnus Hagander
 Me: http://www.hagander.net/
 Work: http://www.redpill-linpro.com/