Re: Performance monitor signal handler

Jan Wieck <JanWieck(at)Yahoo(dot)com> writes:
> Uh - not much time to spend if the statistics should at least
> be half accurate. And it would become worse in SMP systems.
> So that was a nifty idea, but I think it'd cause much more
> statistic losses than I assumed at first.

> Back to drawing board. Maybe a SYS-V message queue can serve?

That would be the same as a pipe: backends would block if the collector
stopped accepting data. I do like the "auto discard" aspect of this
UDP-socket approach.

I think Philip had the right idea: each backend should send totals,
not deltas, in its messages. Then, it doesn't matter (much) if the
collector loses some messages --- that just means that sometimes it
has a slightly out-of-date idea about how much work some backends have
done. It should be easy to design the software so that that just makes
a small, transient error in the currently displayed statistics.

regards, tom lane