Re: windows shared memory error

From: Magnus Hagander <magnus(at)hagander(dot)net>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Andrew Dunstan <andrew(at)dunslane(dot)net>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: windows shared memory error
Date: 2009-05-04 14:14:59
Message-ID: 49FEF863.5040407@hagander.net
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Tom Lane wrote:
> Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
>> Magnus Hagander wrote:
>>> The actual 1 second value was completely random - it fixed all the
>>> issues on my test VM at the time. I don't recall exactly the details,
>>> but I do recall having to run a lot of tests before I managed to provoke
>>> an error, and that with the 1 sec thing i could run it for a day of
>>> repeated restarts without any errors.
>
>> Well, my untested hypothesis is that the actual time required is
>> variable, depending on environmental factors such as machine load.
>
> Seems reasonable.
>
>> So testing repeatedly where such factors are constant might not be good
>> enough. That's why I suggested some sort of increasing backoff, in an
>> attempt to be adaptive.
>
> I still think there's absolutely no evidence suggesting that a variable
> backoff is necessary. Given how little this code is going to be
> exercised in the real world, how long will it take till we find out
> if you get it wrong? Use a simple retry loop and be done with it.

+1. Let's keep it as simple as possible for now. I doubt it's actually
dependent on the *failed* call.

Andrew, you want to write up a patch or do you want me to do it?

//Magnus

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