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Re: [pcp] IB pmda and writing out the default config file

To: Mark Goodwin <goodwinos@xxxxxxxxx>
Subject: Re: [pcp] IB pmda and writing out the default config file
From: Martin Hicks <mort@xxxxxxx>
Date: Tue, 14 Jul 2009 08:21:40 -0500
Cc: Max Matveev <makc@xxxxxxxxx>, pcp@xxxxxxxxxxx
In-reply-to: <4A5C65A3.3050100@xxxxxxxxx>
References: <20090608171828.GA14199@xxxxxxxxxxxxxxxxxxxxxxxxx> <18990.24528.172761.247069@xxxxxxxxxxxx> <20090616182224.GI20783@xxxxxxxxxxxxxxxxxxxxxxxxx> <20090706173919.GC18171@xxxxxxxxxxxxxxxxxxxxxxxxx> <4A5C65A3.3050100@xxxxxxxxx>
User-agent: Mutt/1.5.17 (2007-11-01)
On Tue, Jul 14, 2009 at 09:01:55PM +1000, Mark Goodwin wrote:
> Martin Hicks wrote:
>>> How about this patch.  It rejigs things a lot, but essentially:
>>>
>>> - No config file will be created unless the '-w' flag is passed to
>>>   pmdaib. (this is a change)
>>>
>>> - By default, if no config file is found, only local ports are monitored.
>>>   (before we would always write out a config file containing only local
>>>    ports)
>>>
>>> - If a config file exists then it is the preferred source of information
>>>   and perhaps not even local ports will be monitored. (before you could
>>>   have edited the automatically created file to remove the local ports)
>>>
>>>
>>> So in the case of a user who is using a custom config file (either to
>>> name the instances differently, or to monitor remote ports) who replaces
>>> an HCA, it will be up to them to edit the config file that they created.
>>>
>>> For those who are using the ib pmda in its simplest mode with no config
>>> file, no changes will be necessary when an HCA is replaced but they have
>>> no guarantee of static device naming if they add an additional HCA.
>
> Seems like a reasonable compromise to me. Instance naming in merged
> archives spanning reboots will sometimes be screwed up, but you still
> have the option to avoid that if it really matters. When you look at the
> flaming hoops the scsi and device-mapper folks have jumped thru to
> achieve persistent naming, a more sophisticated scheme isn't warranted; 
> set-and-forget performance monitoring is more important in most cases.

I think I'm going to change things so the '-w' writes the config file
and exits immediately.

I'll also write up a manpage.  This PMDA is fairly complicated and I had
a few "oh, it does that too?" moments while I was doing this work.

mh

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