Magnus Hagander wrote:
On Tue, Oct 19, 2010 at 13:14, Stefan Kaltenbrunner
<ste...@kaltenbrunner.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...
I Think we had some plans to do that - I wonder how hard it would be to
just do the dedicated role thing for now (maybe with the only constraint
that it can only be used on a replication connection) and looking into
making it (technically) less privileged later?
If we want something fixed *now*, should we perhaps just bump the
*default* value for max_wal_senders to 5 or something?
or accept -1 for "unlimited" and use by default, that would fix part of
the complaint from josh but you would still have to restart the master
to implement a limit...
Stefan
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