Re: Autovacuum launcher doesn't notice death of postmaster immediately

Magnus Hagander wrote:
> On Tue, Jun 12, 2007 at 12:23:50PM +0200, Zdenek Kotala wrote:
>> Alvaro Herrera wrote:
>>> Zeugswetter Andreas ADI SD escribió:
>>>>>>>>> The launcher is set up to wake up in autovacuum_naptime
>>>> seconds 
>>>>>>>>> at most.
>>>>>> Imho the fix is usually to have a sleep loop.
>>>>> This is what we have.  The sleep time depends on the schedule 
>>>>> of next vacuum for the closest database in time.  If naptime 
>>>>> is high, the sleep time will be high (depending on number of 
>>>>> databases needing attention).
>>>> No, I meant a "while (sleep 1(or 10) and counter < longtime) check for
>>>> exit" instead of "sleep longtime".
>>> Ah; yes, what I was proposing (or thought about proposing, not sure if I
>>> posted it or not) was putting a upper limit of 10 seconds in the sleep
>>> (bgwriter sleeps 10 seconds if configured to not do anything).  Though
>>> 10 seconds may seem like an eternity for systems like the ones Peter was
>>> talking about, where there is a script trying to restart the server as
>>> soon as the postmaster dies.
>> There is also one "wild" solution. Postmaster and bgwriter will connect 
>>  with socket/pipe and select command will be used instead sleep. If 
>> connection unexpectedly fails, select finish immediately and we are able 
>> to handle this issue asap. This socket should be used also in some 
>> special case when we need wake up it faster.
> 
> Given the amount of problems we've had with pipes on win32, let's try to
> avoid adding extra ones unless they're really necessary. If split-sleep
> works, that seems a safer bet.

Ok It should be problem. But I'm afraid split-sleep is not good solution 
as well. It should generate a lot of race condition in start/stop 
scripts and monitoring tools. Much better should be improve pg_ctl to 
perform clean up ("pg_ctl cleanup) when postmaster fails.

I think we must offer deterministic way to packagers integrator how to 
handle this issue.
    Zdenek