Example session module for ponos (https://github.com/klarna/ponos).

ponos_session.erl

-module(ponos_session).

-behaviour(gen_server).
-export([start/2, init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, code_change/3]).

-record(state, {tasks :: list(), task_state :: any() }).

%% == usage ==
%% 1> ponos_session:start([{print, "Hello"}, {wait, 1000}, {print, "World"}, print_call_count], 0).
%% "Hello"
%% {ok,<0.43.0>}
%% "World"
%% Call count: 3

%% == from ponos ==
%% StartSession = fun() -> ponos_session:start([{print, "Hello"}, {wait, 1000}, {print, "World"}, print_call_count], 0) end.
%% Name         = session_test.
%% LoadSpec     = ponos_load_specs:make_constant(10.0).
%% Options  =  [{duration, 10 * 1000}, {auto_init, false}].
%% Args = [ {name, Name}, {task, StartSession}, {load_spec,LoadSpec}, {options, Options}].
%% [ok] = ponos:add_load_generators([Args]).
%% ponos:init_load_generators([Name]).

%% Public API

start(Tasks, InitState) ->
    gen_server:start_link(?MODULE, [Tasks, InitState], []).

%% Callbacks

init([Tasks, InitState]) ->
    self() ! next_task,
    {ok, #state{ task_state = InitState, tasks = Tasks}}.

handle_call(_Request, _From, State) ->
    {reply, ok, State}.


handle_cast(_Msg, State) ->
    {noreply, State}.


handle_info(next_task, #state{task_state = TaskState, tasks = [NextTask | Tasks]}) ->
    NewTaskState = handle_task(NextTask, TaskState),
    NewState     = #state{task_state = NewTaskState, tasks = Tasks},
    case Tasks of
        [] ->
            {stop, normal, NewState};
        _ ->
            self() ! next_task,
            {noreply, #state{task_state = NewTaskState, tasks = Tasks}}
    end.

terminate(_Reason, _State) ->
    ok.

code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

handle_task({wait, Millisecords}, TaskState) ->
    timer:sleep(Millisecords),
    TaskState + 1;

handle_task({print, Data}, TaskState) ->
    io:format("~p\n", [Data]),
    TaskState + 1;

handle_task(print_call_count, TaskState) ->
    io:format("Call count: ~p\n", [TaskState]),
    TaskState + 1.