Re: src/test/subscription/t/002_types.pl hanging on particular environment

On 19/09/17 14:33, Amit Kapila wrote:
> On Tue, Sep 19, 2017 at 3:34 PM, Petr Jelinek
> <petr.jelinek@2ndquadrant.com> wrote:
>> n 18/09/17 18:42, Tom Lane wrote:
>>
>>> So, frankly, I think we would be best off losing the "logical rep
>>> worker slot" business altogether, and making do with just bgworker
>>> slots.
> 
> I think that would be cleaner as compared to what we have now.
> 
>>>  The alternative is getting the postmaster involved in cleaning
>>> up lrep slots as well as bgworker slots, and I'm going to resist
>>> any such idea strongly.  That way madness lies, or at least an
>>> unreliable postmaster --- if we need lrep slots, what other forty-seven
>>> data structures are we going to need the postmaster to clean up
>>> in the future?
>>>
>>> I haven't studied the code enough to know why it grew lrep worker
>>> slots in the first place.  Maybe someone could explain?
>>>
>>
>> I am not quite sure I understand this question, we need to store
>> additional info about workers in shared memory so we need slots for that.
>>
> 
> Yeah, but you could have used the way we do for parallel query where
> we setup dsm and share all such information.  You can check the logic
> of execparallel.c and parallel.c to see how we do all such stuff for
> parallel query.
> 

I don't understand how DSM helps in this case (except perhaps the memory
allocation being dynamic rather than static). We still need this shared
memory area to be accessible from other places than launcher (the
paralllel query has one lead which manages everything, that's not true
for logical replication) and we need it to survive restart of launcher
for example, so all the current issues will stay.

-- 
  Petr Jelinek                  http://www.2ndQuadrant.com/
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