Awesome

erlang-mesos

An erlang binding for mesos. Currently supports the 0.25.0 version - see releases for previous releases.

How does it work

erlang-mesos has been implemented as a nif. Messages are sent via the nif to mesos and mesos callbacks into erlang asynchronously. Although nifs are never ideal the asynchronous implmentaion of mesos lends itself nicely in this case.

The modules - scheduler.erl and executor.erl are directly equivialant to their counterparts in mesos. To add your own mesos scheduler or framework you implement the behaviours that they expose.

For example a basic scheduler would look like this -

-behaviour (scheduler).

init(_) ->
    FrameworkInfo = #'FrameworkInfo'{user="", name="My Framework"},
    MasterLocation = "127.0.1.1:5050",
    State = [],
    {FrameworkInfo, MasterLocation, State}.

registered(FrameworkID, MasterInfo, State) -> {ok,State}.

reregistered(MasterInfo, State) -> {ok,State}.

resourceOffers(Offer, State) -> {ok,State}.

disconnected(State) -> {ok,State}.

offerRescinded(OfferID, State) -> {ok,State}.

statusUpdate(StatusUpdate, State) -> {ok,State}. 

frameworkMessage(ExecutorID, SlaveID, Message, State) -> {ok,State}.

slaveLost(SlaveID, State) -> {ok,State}.

executorLost(ExecutorID, SlaveID, Status, State)-> {ok,State}.

error(Message, State) -> {ok,State}.

There is an example framework (scheduler) and executor in the src directory.

There is also an example of using erlang-mesos in an OTP application at merkxx.

Future

I want to move the implementation to use the low level wire protocol. As details emerge this api wrapper will move away from the nif implementation to becoming a native erlang implementation. This will of course be "safer" in an erlang context

Getting started

Install mesos

The vagrant file I use for dev testing is at https://github.com/mdevilliers/vagrant-mesos-development-environment. It can be pointed at the version of mesos you wish to develop against plus installs erlang, gcc, git ect.

Install the protobuf tools.

sudo apt-get install libprotobuf-dev protobuf-compiler

git clone .....
cd erlang-mesos

Get the project dependancies

./rebar get-deps

Compile the application including the generated modules from the .proto file

./rebar compile

After that you should be all set with a

./rebar compile skip_deps=true

To run the example framework from a command window

erl -pa ebin 
scheduler:start_link( example_framework, "127.0.1.1:5050").

Note this will only work on a single node (development) cluster due to the way the example executor is found. This is only for convenience whilst developing.

Best Practice

erlang-mesos is a new library interfacing over a nif to a rapidly changing library so at least initally I would recommend running it in another erlang node.

Help

To debug mesos you can use the following enviromental variable before starting up the erlang runtime.

GLOG_v=1 erl -pa ebin

Thanks

Special thanks goes to mokele for the acceptOffer implementation.

mesos-go was an extremely helpful examplar