Re: [pcp] automatic derived metrics slowing down remote pcp clients, esp. pmlogconf

[Ken McDonell <kenj@xxxxxxxxxxxxxxxx>]

On 15/05/16 08:22, Mark Goodwin wrote:
> ...
> patch looks good - HOWEVER, thinking about this a bit more, ideally if
> a pmlogger config (or pmlogconf config) asks for a derived metric to be
> logged,
> it should expand this and log the leaf operand metrics.
-1 from me.

pmlogger should continue to log derived metrics.  If you don't do this, 
then the archive cannot be properly replayed unless you also carry 
around the derived metric definitions.
Consider

foo = real.metric.a + real.metric.b

user asks to log foo (potentially from a pmchart "record" operation, 
where the definition of foo may not be visible or obvious).
Then the user sends the archive off to someone else for analysis ... and 
"foo" remains a complete mystery ... the archive only contains 
real.metric.a and real.metric.b.