Re: [HACKERS] Re: [HACKERS] Re: [HACKERS] Re: [HACKERS] Windows service is not starting so there’s message in log: FATAL: "could not create shared memory segment “Global/PostgreSQL.851401618”: Permission denied”

On Tue, May 17, 2016 at 4:16 AM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> On Mon, May 16, 2016 at 9:45 AM, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>
> wrote:
>>
>> On Sun, May 15, 2016 at 3:34 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
>> wrote:
>> > Sounds sensible, but if we want to that route, shall we have some
>> > mechanism
>> > such that if retrying it for 10 times (10 is somewhat arbitrary, but we
>> > retry 10 times in PGSharedMemoryCreate, so may be there is some
>> > consistency)
>> > doesn't give us unique name and we are getting EACCES error, then just
>> > throw
>> > the error instead of more retries. This is to ensure that if the API is
>> > returning EACCES due to reason other than duplicate handle, then we
>> > won't
>> > retry indefinitely.
>>
>> The logic in win32_shmem.c relies on the fact that a segment will be
>> recycled, and the retry is here because it may take time at OS level.
>> On top of that it relies on the segment names being unique across
>> systems. So it seems to me that it is not worth the complication to
>> duplicate that logic in the dsm implementation.
>
> If we don't do retry for fixed number of times, then how will we handle the
> case if EACCES is due to the reason other than duplicate handle?

EACCES is a bit too low-level... I had in mind to check GetLastError
with only ERROR_ACCESS_DENIED, and retry only in this case, which is
the case where one postmaster is trying to access the segment of
another.
--
Michael