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

[Christopher Phillips]

  Hmm, I've had so little experience with tuntap interfaces I didn't think
of them. That sounds like the way to go to get things working on OSX,
though at a much larger amount of effort (both the learning curve on my
part, and re-implementing the degradation behaviors I get for free from the
kernel). Thanks for suggesting it; once I get things to where it's usable
on Linux in all the ways I want, some research and a rewrite may be in
order to get it fully portable.

On Mon, Jan 5, 2015 at 8:11 PM, Michael Santos <michael.santos@REDACTED>
wrote:

> On Mon, Jan 05, 2015 at 09:16:42AM -0500, Christopher Phillips wrote:
> > For OSX ipfw was deprecated in Lion and removed in Yosemite. I've done a
> > bit of looking at the replacement, pf, and it looks like dropping packets
> > based on percentage is doable, as is bandwidth throttling (something I'd
> > like to add, in general), but I don't see any way to induce a delay,
> beyond
> > an implicit one based on tos prioritization. If someone knows how and can
> > point me in the right direction I'd appreciate it.
>
> The portable way is to use a tuntap device. Then you can arbitrarily
> drop packets, throttle bandwidth, introduce latency, whatever, from your
> code. Sort of like quickcheck for networks :)
>
> > On Mon, Jan 5, 2015 at 6:52 AM, Sergej Jurečko <sergej.jurecko@REDACTED
> >
> > wrote:
> >
> > > 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" <lostcolony@REDACTED>
> > > 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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> > >> http://erlang.org/mailman/listinfo/erlang-questions
> > >>
> > >>
>
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>
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