[Gllug] Modern Fault finding techniques

[Aaron Trevena]

On 17 November 2011 19:03, James Courtier-Dutton <james.dutton at gmail.com> wrote:
>> So the question is, what do people consider newer better technologies. The
>> interview question was "A user phones up and say the page on the web site is
>> very slow".

That's a good open-ended discussion question in interviews and
appropriate for both developers and sysadmins.

If it's not a app dev or app support role I wouldn't expect somebody
to talk through troubleshooting an app aside from some basic ballpark
stuff, but I would expect a sysadmin to be able to help isolate the
problem so that the right team are (re-)assigned the trouble ticket.

There are plenty of system level things that could be problematic that
a sysadmin would be in a  better position to spot : heavy IO, flakey
network connections to other systems the application uses - not just
databases - there could be nosql applications, memcached, mogilefs etc
that are causing problems, some clustering apps support multiple
fallback handling so the app won't see errors, but under the cover a
web page request could be making multiple attempts to reach a resource
on a different load balanced machine, there are also fun things like
the number of apache processes rapidly increasing because part of the
application is waiting for a slow database query or an overloaded
resource elsewhere.

The thing is, system administration can and should be more than just
making sure the operating system on a given machine is running
smoothly without any applications running - and system administrators
are part of a team, working with developers and support and hopefully
providing tools or knowledge that enables them to resolve or prevent
problems - not just putting there hands up and saying "oh that's a
software/hardware/application/support problem - not my area.. I'm off
on a fag break" ;)

A.

-- 
Aaron J Trevena, BSc Hons
http://www.aarontrevena.co.uk
LAMP System Integration, Development and Consulting
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