[ixpmanager] sflow daemon

[Rowan Thorpe]

> Is sflowtool supposed to be daemonized, or is there a script that
> kicks it off?  It feels like I am missing a piece.

Daemon. It seems there might be two areas for improvement in the
documentation(?):

1) I can't find a link from the standard "installation instructions"
page to the sflow installation page, I only find it by navigating via
"pages" on the github wiki...

2) The sflow installation page doesn't explicitly state how/when to
install/configure/run sflowtool (other than including it in the example
package list for FreeBSD). Even adding "sflowtool must be run as a
daemon, independently of IXP-Manager - whether via init or cron, etc."
to the "Configuring sflowtool" section might be enough?

NB: A small gotcha which bit me hard was that because I was integrating
IXP-Manager onto a server which was also cloning other functionality
from a previous server, there was already a script running sflowtool on
a separate port for unrelated data-collection. Unfortunately it was
running from root crontab rather than system cron (or better yet - init)
and every few days it would do a "killall sflowtool, archive log-file,
re-run sflowtool" cycle, with no logging of the fact. It took me
a while (longer than I'd like to admit) to diagnose why the IXP-M
sflowtool was dying every few days...

FWIW: a month or two ago I posted an ITP (intent to package) and I
packaged and uploaded a Debian package (therefore Ubuntu, etc) for
sflowtool to the mentors server at Debian and asked for a Debian
Developer to sponsor getting it into the official repos (I also
included an init-script I wrote for it - which should be
platform-agnostic enough BTW), but no-one responded yet :-( In the
process I even shook out some small sflowtool bugs and helped the
upstream sflowtool developer to patch them, hence the recent version
bump of that too :-) If anyone knows a Debian Developer who might want
to sign and push my packaging efforts so that sflowtool can become
easier to install on lots of systems, please urge them to visit and give
input/feedback: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=724939

-- 
Rowan Thorpe
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