Re: [pcp] pcp grafana and graphite - How to convert pcp metric values into percent

[Amer Ather <aather@xxxxxxxxxxx>]

Great information!Â

I somehow misunderstood the scope of derived PCP metrics. It make sense if taking into account PCP design philosophy not to keep monitoring client state information. ÂOur interest in PCP as a on-demand tool was mainly due to this design. We don't want to have another tool on the system collecting system stats and adding overhead. We want to use PCP as a troubleshooting tool where high resolution data collection is triggered on-demand basis to debug the issue.

With PCP graphite integration, we also like to evaluate PCP archives/logging feature as a replacement to sar to log historical data. ÂUsing web graphite client (like grafana), we can build intuitive graphs for data correlation to help us discover anomalies quickly.

Question:

I want to make we are implementing the logic on web client correctly. Let's say PMAPI client is fetching metrics at a second interval. To process it one show do the following:

• fetch the given metric, say kernel.all.cpu.idle
• calculate the delta
• Apply rate conversion. As Nattan pointed out,Âcounters need toÂbe converted into a rate (change-in-value over change-in-time) and Âunits (milli-seconds) converted into a utilization by multiplying by 100Âto produce a percent: "kernel.pct.cpu.idle = 100 * kernel.all.cpu.idle / hinv.ncpu". Metric hinv.ncpu can be cached considering it does n't change.

Thanks for all your help,

Regards,

Amer.

On Wed, Jul 2, 2014 at 1:39 PM, Frank Ch. Eigler <fche@xxxxxxxxxx> wrote:

Hi, Ken -

> [...] Âso the 20th anniversary of "starting" PCP has been and gone.
> [...]

Congrats!

> ... so, over 20 years ago, we made a very early decision to NOT hold

> client state in the collection (server) side of the PMAPI. Â[...] ÂI

> still believe this is semantically the correct thing to do ...
> clients, not pmcd, know what to do with a time series of metric

> observations. [...]

Indeed so. ÂA new issue under contention is whether the client side of
PMAPI - libpcp - could/should have rate-conversion capabilities, so
each client programs wouldn't have to reinvent that wheel.

- FChE

--

Thanks,

Amer Ather

Cloud Performance Engineering

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