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Re: linux interface, pcp protocol, tutorials

To: adrian.lukas@xxxxxxxxxxxxxxxxxxxxx
Subject: Re: linux interface, pcp protocol, tutorials
From: Max Matveev <makc@xxxxxxx>
Date: Fri, 9 Mar 2001 18:34:35 +1100 (EST)
Cc: PCP Mails <pcp@xxxxxxxxxxx>
In-reply-to: <200103071812.f27ICuA02857@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
References: <200103071812.f27ICuA02857@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
Sender: owner-pcp@xxxxxxxxxxx
>>>>> "al" == adrian lukas <adrian.lukas@xxxxxxxxxxxxxxxxxxxxx> writes:

 al> 1. Are any tutorials that describe some "pcp linux sessions"? 
 al> In the "Admin's Guide" i read something about a "Tutorial".
 al> Is this tutorial available only for irix?

At the moment - yes. It could appear on Linux one day, provided we
will find time to check for Irix-isms and update it where necessary.

 al> After building and installing the package, i made some tests
 al> (pminfo).  There were no metrics defined in any metric name
 al> space. It takes me some time to realize that the standard name
 al> spaces must be builded too.  Unfortunately in the standard docs i
 al> didn't found any remarks about that.

There is a bit of magic which is done for the user who installs RPMs -
if file /var/pcp/pmns/.NeedRebuild exist, next time
/etc/rc.d/init.d/pcp starts, it will rebuild the name
space. Unfortunately, there is no install line for that file - we
don't want it to be part of RPM because rpm(1) will complain after we
remove it.

In general, we don't expect Mrs User to do it - it's done
automagically by pcp startup script and it's done by PMDAs'
Install/Remove scripts, whence lack of documentation.

BTW, there is also /var/pcp/config/magic/.NeedUpdate.

 al> 2. In the "Admin's Guide" are some pcp tools described that
 al> are not present on linux distribution (at least on my box).
 al> Is that normal or i forget something? (example: pmchart)

It's normal: those tools are in the pcp-pro - another RPM which we
ship as binary only.

 al> 3. What interface uses pcp to collect data on a linux host?
 al> Here i mean operating system specific data (linux metric name space),
 al> that refer to os activity (memory, processes, etc).
 al> Is /proc fs the "hole" linux interface?

"hole" as in "whole"? Mostly yes. Some people refer to PCP as
"distributed /proc".

 al> 4. Where can i find a specification of the pcp communication
 al> protocol? (here i mean "pcp" protocol, not TCP/IP).

Do you mean over the wire protocol? I'm affraid there is no formal
written specification, or at least I haven't seen one yet, - but
sniffing around src/libpcp/src/pdu.c will uncover few interesting
things.

 al> (I read something about a text and a binary protocol...)

We normally use binary protocol, ie. values are sent as numbers and
not as ascii strings. Ascii protocol is mostly for debugging.

max

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