Re: Performance monitor signal handler

At 13:49 16/03/01 -0500, Jan Wieck wrote:
>
> Similar problem as with shared memory - size. If a long
> running backend of a multithousand table database needs to
> send access stats per table - and had accessed them all up to
> now - it'll be alot of wasted bandwidth.

Not if you only send totals for individual counters when they change; some
stats may never be resynced, but for the most part it will work. Also, does
Unix allow interrupts to occur as a result of data arrivibg in a pipe? If
so, how about:

- All backends to do *blocking* IO to collector.

- Collector to receive an interrupt when a message arrives; while in the
interrupt it reads the buffer into a local queue, and returns from the
interrupt.

- Main line code processes the queue and writes it to a memory mapped file
for durability.

- If collector dies, postmaster starts another immediately, which slears
the backlog of data in the pipe and then remaps the file.

- Each backend has its own local copy of it's counters which *possibly* to
collector can ask for when it restarts.

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