From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Dominique Devienne <ddevienne(at)gmail(dot)com> |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: libpq v17 PQsocketPoll timeout is not granular enough |
Date: | 2024-06-10 16:18:19 |
Message-ID: | 740207.1718036299@sss.pgh.pa.us |
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Lists: | pgsql-general |
Dominique Devienne <ddevienne(at)gmail(dot)com> writes:
> PQsocketPoll() being based on time_t, it has only second resolution, AFAIK.
> Despite the [underlying implementation in fe-misc.c][2] supporting at
> least milliseconds.
> ...
> But I think it would a pity if that unreleased API couldn't be made to
> accomodate sub-second timeouts and more use-cases, like above.
> Especially given that libpq v17 isn't out yet. I may come late to the
> game, but hopefully it is not too late.
This is an interesting suggestion, but I think yes it's too late.
We're already past beta1 and this'd require some fairly fundamental
rethinking, since there's no easy substitute for type time_t that has
millisecond resolution. (The callers do want to specify an end time
not a timeout interval, since some of them loop around PQsocketPoll
and don't want the end time to slip.)
I guess conceivably we could use gettimeofday() and struct timeval
instead of time() and time_t, but it'd touch a lot of places in
libpq and it'd make some of the calculations a lot more complex.
Maybe a better idea would be to convert to using our
src/include/portability/instr_time.h abstraction? But that
would be problematic for outside callers.
In any case this doesn't seem like a sane thing to be redesigning
post-beta. A few months ago maybe we'd have done it, but ...
regards, tom lane
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