At 06:57 15/03/01 -0500, Jan Wieck wrote:
>
> And shared memory has all the interlocking problems we want
> to avoid.
I suspect that if we keep per-backend data in a separate area, then we
don;t need locking since there is only one writer. It does not matter if a
reader gets an inconsistent view, the same as if you drop a few UDP packets.
> What about a collector deamon, fired up by the postmaster and
> receiving UDP packets from the backends.
This does sound appealing; it means that individual backend data (IO etc)
will survive past the termination of the backend. I'd like to see the stats
survive the death of the collector if possible, possibly even survive a
stop/start of the postmaster.
> Now whatever the backend has to tell the collector, it simply
> throws a UDP packet into his direction. If the collector can
> catch it or not, not the backends problem.
If we get the backends to keep the stats they are sending in local counters
as well, then they can send the counter value (not delta) each time, which
would mean that the collector would not 'miss' anything - just it's
operations/sec might see a hiccough. This could have a sidebenefit that(if
wewanted to?) we could allow a client to query their own counters to get an
idea of the costs of their queries.
When we need to reset the counters that should be done explicitly, I think.
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