[CentOS] best parallel / cluster SSH

[Les Mikesell]

On 2/4/2010 12:31 PM, Alan McKay wrote:
>> It depends on what you need to do.  If you really have enough machines
>> or long-running jobs that a shell loop through them isn't practical, you
>> might want something higher-level like cfengine or puppet, or at least
>> something running under cron to make them independent.
>
> cfengine or puppet (or something else - slackmaster?) are where I want
> to be eventually - but in the immediate term something like this would
> help a lot.    e.g bouncing my 4 front-end apache servers on 4
> different boxes.   That sort of thing.

Usually for that sort of thing I explicitly _don't_ want all of a group 
to be out of service at the same moment so I much prefer to:

for host in host1 host2 host3 host4
do
echo $host
ssh $host service httpd restart
done

which doesn't take much more thought then doing it locally and if I 
expect to repeat it I can save the commands in a script.

> I was actually going to start another "configuration management redux"
> thread as a follow up to a thread I started a few months ago.

I'm interested in the topic, but most of what I've seen just add 
complexity for no particular reason.  Clustering ssh commands might be 
an exception for a certain subset of things that need to happen at 
approximately the same time on multiple machines (and you are willing to 
risk breaking them all at once with a typo).

-- 
   Les Mikesell
    lesmikesell at gmail.com