Re: shared-memory based stats collector

Hi,

On 2018-07-06 22:03:12 +0200, Magnus Hagander wrote:
> *If* we can provide the snapshots view of them without too much overhead I
> think it's worth looking into that while *also* proviiding a lower overhead
> interface for those that don't care about it.

I don't see how that's possible without adding significant amounts of
complexity and probably memory / cpu overhead. The current stats already
are quite inconsistent (often outdated, partially updated, messages
dropped when busy) - I don't see what we really gain by building
something MVCC like in the "new" stats subsystem.

> If it ends up that keeping the snapshots become too much overhead in either
> in performance or code-maintenance, then I agree can probably drop that.
> But we should at least properly investigate the cost.

I don't think it's worthwhile to more than think a bit about it. There's
fairly obvious tradeoffs in complexity here. Trying to get there seems
like a good way to make the feature too big.

Greetings,

Andres Freund