Re: max_standby_delay considered harmful

Simon Riggs wrote:
> On Wed, 2010-05-12 at 08:52 -0400, Robert Haas wrote:
>> On Wed, May 12, 2010 at 7:26 AM, Simon Riggs <simon@2ndquadrant.com> wrote:
>>> On Wed, 2010-05-12 at 07:10 -0400, Robert Haas wrote:
>>>
>>>> I'm not sure what to make of this.  Sometimes not shutting down
>>>> doesn't sound like a feature to me.
>>> It acts exactly the same in recovery as in normal running. It is not a
>>> special feature of recovery at all, bug or otherwise.
>> Simon, that doesn't make any sense.  We are talking about a backend
>> getting stuck forever on an exclusive lock that is held by the startup
>> process and which will never be released (for example, because the
>> master has shut down and no more WAL can be obtained for replay).  The
>> startup process does not hold locks in normal operation.
> 
> When I test it, startup process holding a lock does not prevent shutdown
> of a standby. 
> 
> I'd be happy to see your test case showing a bug exists and that the
> behaviour differs from normal running.

In my testing the postmaster simply does not shut down even with no 
clients connected any more once in a while - most of the time it works 
just fine but in like 1 out of 10 cases it get's stuck - my testcase (as 
detailed in the related thread) is simply doing an interval load on the 
master (pgbench -T 120 && sleep 30 && pgbench -T 120 - rinse and repeat 
as needed) and pgbench -S && pg_ctl restart && pgbench -S in a lop on 
the standby. once in a while the standby will simply not shut down 
(forever - not only by eceeding the default timeout of pgctl which seems 
to get triggered much more often on the standby than on the master - 
have not looked into that yet in detail)


Stefan