On 03/07/14 03:57, Amer Ather wrote:> Frank and Nathan,
>
> So what I understand that rate conversion does not work for PMWEBAPI
> client but works fine for pmval and pmwebd graphite extension.
Just to back up what Frank said, ...
When we designed the PCP architecture ...
[Historical aside, Nathan mentioned seeing a 1995 copyright notice in
the code, and speculated on a PCP 20-year anniversary ... I've checked
my records and the conceptual design of PCP started in early 1993, but
it was not until late 1993 or early 1994 that the first code was
written, so the 20th anniversary of "starting" PCP has been and gone.
But we barely had source control then, and certainly no obligations to
add copyrights ahead of the initial product shipping in 1995].
... so, over 20 years ago, we made a very early decision to NOT hold
client state in the collection (server) side of the PMAPI. We wanted
the potential memory bloat from holding a history of previous values for
all clients to live with the clients (that were running on workstations)
not on the server(s).
I still believe this is semantically the correct thing to do ...
clients, not pmcd, know what to do with a time series of metric
observations.
So pminfo, pmprobe, pmlogger and PMWEBAPI all sit close PMAPI and choose
not to implement rate conversion, but all the other end-user clients
like pmval, pmie, pmchart, pmview, pmdumpstats, ... do implement rate
conversion (in addition to other more exotic post-processing of the time
series of metric values).
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