Re: [HACKERS] Re: Reducing sema usage (was Postmaster dies with many child processes)

Tom Lane wrote:
>Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> writes:
>> If they asked for 64 backends, we better be able go give them to them,
>> and not crash or fail under a load. 64 semaphores is nothing.
>
>That argument would be pretty convincing if pre-grabbing the semaphores
>was sufficient to ensure we could start N backends, but of course it's
>not sufficient. The system could also run out of processes or file
>descriptors, and I doubt that it's reasonable to grab all of those
>instantly at postmaster startup.

The major problem at the moment is not that a new backend fails, but
that it brings down everything else with it. How about having a new
backend set a one-byte flag in shared memory when it has
finished setting itself up? as long as the flag is unset, the
backend is still starting itself up, and a failure will not require
other backends to be brought down.

--
Oliver Elphick Oliver(dot)Elphick(at)lfix(dot)co(dot)uk
Isle of Wight http://www.lfix.co.uk/oliver
PGP key from public servers; key ID 32B8FAA1
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