hannu at skype.net writes:
> Is it true (as I think it is) that running pg_dump on master database will
> stall replication ?
>
> If the reason is long-held transaction, could we do something about it,
> like trying to run pg_dump in some kind of read-only mode ?

It will halt things iff the pg_dump includes the Slony-I cluster
schema, because the 'generate Sync' event that Slony-I periodically
raises does an explicit
  "LOCK _slonyschema.sl_event;"

That winds up waiting for the pg_dump to finish, and all the other
Slony-I work that is trying to access sl_event sits and waits behind
that.

You can evade the problem if you can pg_dump just the schemas that you
need, and avoid pg_dump'ing the Slony-I cluster schema.  We've been
able to make use of that evasion.

There will doubtless be some discussions as to whether the lock could
be a little less intrusive; it's not self-evident whether the present
policy is forcibly necessary, or if some less exclusive lock could be
sufficient.
-- 
"cbbrowne","@","ca.afilias.info"
<http://dev6.int.libertyrms.com/>
Christopher Browne
(416) 673-4124 (land)