Re: Streaming replication status

On Sun, 2010-01-10 at 12:10 -0800, Josh Berkus wrote:
> > We need monitoring anywhere we have a max_* parameter. Otherwise we
> > won't know how close we are to disaster until we hit the limit and
> > things break down. Otherwise we will have to set parameters by trial and
> > error, or set them so high they are meaningless.
>
> I agree.
>
> Thing is, though, we have a de-facto max already ... when pgxlog runs
> out of disk space.

What I mean is this: The purpose of monitoring is to avoid bad things
happening by being able to predict that a bad thing will happen before
it actually does happen. Cars have windows to allow us to see we are
about to hit something.

> And no monitoring *in postgresql* for that, although
> obviously you can use OS monitoring for it.

PostgreSQL doesn't need to monitor that. If the user wants to avoid
out-of-space they can write a script to monitor files/space. The info is
accessible, if you wish to monitor it.

Currently there is no way of knowing what the average/current transit
time is on replication, no way of knowing what is happening if we go
idle etc.. Those things need to be included because they are not
otherwise accessible. Cars need windows, not just a finely tuned engine.

--
Simon Riggs www.2ndQuadrant.com