[erlang-questions] [ANN]: Damocles, a library for testing distribution scenarios on a single machine

Sergej Jurečko <>
Mon Jan 5 12:52:57 CET 2015


This looks like a great tool and something that could easily be added to
unit tests.
Anyone with ipfw skills to add bsd/osx support?

Sergej
On Jan 5, 2015 1:41 AM, "Christopher Phillips" <> wrote:

> https://github.com/lostcolony/damocles
>
> I asked a while back on this mailing list if anyone had any useful
> libraries or similar for testing distribution scenarios. I only got back a
> few responses (maybe co-op riak_test? Maybe make use of the underlying
> Linux traffic control and network emulation apps?), and my own searches,
> while finding a few libraries, didn't find anything I could easily co-op
> for my purposes.
>
> To that end, I went ahead and spent part of my break on this, and it just
> got sufficiently feature complete to throw out there. I haven't had a
> chance to really start using it heavily, and I've only been testing it on
> my dev box, but a basic run through of the functionality as I typed up the
> readme worked (so any issues being pointed out would be appreciated).
> Essentially, it allows you to create and manipulate local interfaces on a
> Linux machine to emulate packet delay and loss (using the underlying
> traffic control and network emulation mechanisms), with a number of
> convenience methods to (hopefully) easily describe fairly intricate
> distribution scenarios.
>
> Things like "create these 5 interfaces, (now from my test code, launch a
> copy of my app on each one, or even a different app on one of them, to see
> what happens when that resource is flaky); now make it so 1 and 2 can't
> talk to 3 and 4, and vice versa, but everyone can still talk to 5, but
> replies have a 50% chance of being dropped from 5 when responding to 1 and
> 2, and there's a 300ms delay between 3 and 4; (now, let's run more of our
> test code to assert that trying to write to any node still succeeds); okay,
> now let's restore the network back to normal (and have our test code make
> sure the write was retained)", or whatever, can be set up in a
> straightforward, automated manner as part of a common test run, and not be
> reliant on certain VMs being up, nor the tests being run on a specific
> network. The tradeoff, obviously, being that you can't really load test
> things with it. Still, it fits my basic needs, and I figured it might be of
> use to others.
>
> I'll be adding some simple examples when I next get free time (I ran out
> of it from the holiday break without getting to them; dunno when I will),
> and will try and get to any bugs or simple suggestions in a timely manner,
> but hopefully it's fairly straightforward and useful as is.
>
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