Usability notes from using runit for the first time

From: Kevin Burke <>
Date: Sat, 8 Feb 2014 22:32:56 -0800

Recently I set up a daemon to monitor server load, that's monitored by
runit. I ran into a few problems that ended up taking the better part of a
day to debug, so I wanted to note them here.

*Despite starting a single Python process via runit, after about 20 minutes
several Python processes would be running on the host.* The problem, it
turns out, was that I wasn't using exec() to replace the `run` script with
my Python process. It may be worth noting this in the FAQ; something like
"I started my service with runit, but it looks like several instances are
running" and tell people to ensure they started their service with exec. It
may also be worth telling people that if monitored via top() or similar,
your running program must appear as a child of runsvdir for runsv to
effectively monitor it.

*Second, changes to my `run` script weren't being picked up by runs v. *I
havne't double checked this, but I believe running "sv down <service>; sv
up <service>" was not enough for runit to pick up changes in my program's
`run` file. Only after I removed the /service/myservice directory were the
changes picked up. Again, I haven't double checked this but if this is
actually the program's behavior then it may be worth noting this in a FAQ.

*Third, does runsv log anywhere*, or can it be run in a debug mode? When I
saw multiple processes popping up in the process list, my intuition was to
try and enable debug logs to figure out what was doing on.

Finally, I would like to restart the process if it is using too much
memory. Reading the `chpst` man page reveals this:

*-m bytes:* limit memory. Limit the data segment, stack segment, locked
physical pages, and total of all segment per process to bytes bytes each.

What is the actual behavior if the process tries to use more memory than it
is allowed? Will it (can it) just restart the process?

Thanks for your help! runsv/chpst are awesome tools and I'm glad they are
so good.


Kevin Burke | Twilio
phone: 925.271.7005 |
Received on Sun Feb 09 2014 - 06:32:56 UTC

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