Purpose

A task queue in Elixir.

Usage

Initialization

Call TaskQueue.WorkersSupervisor.init(num_workers) to initialize the queue with num_workers workers.

Start a task

Each task is given by:

• A task_id
• A function to execute when a task starts
• A list of parameters for this function
• A timeout (nil means no timetout)
• A function that will be called when the task ends
• A list of parameters for this function

WARNING : the function to execute when a task ends MUST take one additional parameters of the form

%{result: result, timeout: has_timeouted}

which gives the function result and indicates whether the execution terminated because of a timeout.

Call

GenServer.call(TaskQueue.WorkersSupervisor, %{
    start_infos: %{module: <the start function module>,
                   function: :start_fct_name,
                   params: <the list of params>,
                   timeout: <the timetout>},
    task_id: task_id,
    end_infos: %{module: TaskQueue.WorkersSupervisor,
                 function: :end_fct_name,
                 params: end_params}
  }
)

to start a task.

Kill a task

Call

GenServer.call(TaskQueue.WorkersSupervisor, %{kill: task_id})

To kill the task with id task_id.

If the task is still in the queue it will not be executed and the function given in :end_infos will be directly executed when the task turn comes.

If the task is running it will be killed immediately and the function given in :end_infos will be directly executed.

Cancel a task

Call

GenServer.call(TaskQueue.WorkersSupervisor, %{
  cancel: %{module: <the cancel function module>,
            function: :cancel_fct_name,
            params: <the list of params>}, task_id: task_id
})

To cancel the task with id task_id.

If the task is still in the queue it will not be executed and the function given in :end_infos will be directly executed when the task turn comes.

If the task is running, the function cancel_fct_name will be called (and nothing more). The function is meant to gently kill the task.