Re: How to get archived/historical metrics for network.tcpconn.* items

On 30/11/16 05:32, [email protected] wrote:
> I wanted to know how I could get archived or historical metrics for the
> network.tcpconn.* items. For example, when I do a pminfo -dfmtT
> network.tcpconn.time_wait I get the expected output.
> network.tcpconn.time_wait PMID: 60.19.6 [Number of TIME_WAIT connections]
>     Data Type: 32-bit unsigned int  InDom: PM_INDOM_NULL 0xffffffff
>     Semantics: instant  Units: count
> Help:
> Number of TIME_WAIT connections
>     value 26
>
> If I try to get the information from one of the files under pmlogger the
> information ist not in it. Also I don't see the metrics in the
> pmlogger.log file like I see the other metrics. Do I need to add the
> network.tcpconn.* metrics somewhere like /var/lib/pcp/config/pmlogconf?

G'day William.

Frank's confirmed your suspicion, but there is a general principle here, 
namely on a given host, pmcd and the associated PMDAs expose a myriad of 
metrics.  But not all of these are of interest on any particular host 
running a specific mix of workloads.  As a consequence, pmlogger 
collects (in the archives) only a subset of the available metrics at 
specific sampling rates.

Serious use of PCP archives for retrospective performance analysis will 
often require some local customization of the pmlogger configuration to:

(a) add metrics you're interested in,
(b) cull metrics you have no interest in, and
(c) refine the sampling rates.

This is a bit of an iterative balancing act ... on the one hand you want 
just those metrics that are known to be of interest, and on the other 
you want to capture those metrics that _might_ reasonably be of interest 
in the future.

Make the pmlogger config too narrow and you'll miss metrics or sample 
less frequently than required, make it too broad and pmlogger (and more 
critically pmcd and the PMDAs may become a significant load) and the 
size of the archives gets out of control.

Good luck.



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