Supervisor.Spec (Elixir v1.12.0-dev) View Source

This module is deprecated. Use the new child specifications outlined in the Supervisor module instead.

Outdated functions for building child specifications.

The functions in this module are deprecated and they do not work with the module-based child specs introduced in Elixir v1.5. Please see the Supervisor documentation instead.

Convenience functions for defining supervisor specifications.

Example

By using the functions in this module one can specify the children to be used under a supervisor, started with Supervisor.start_link/2:

import Supervisor.Spec

children = [
  worker(MyWorker, [arg1, arg2, arg3]),
  supervisor(MySupervisor, [arg1])
]

Supervisor.start_link(children, strategy: :one_for_one)

Sometimes, it may be handy to define supervisors backed by a module:

defmodule MySupervisor do
  use Supervisor

  def start_link(arg) do
    Supervisor.start_link(__MODULE__, arg)
  end

  def init(arg) do
    children = [
      worker(MyWorker, [arg], restart: :temporary)
    ]

    supervise(children, strategy: :simple_one_for_one)
  end
end

Note that in this case we don't have to explicitly import Supervisor.Spec since use Supervisor automatically does so. Defining a module-based supervisor can be useful, for example, to perform initialization tasks in the Supervisor.init/1 callback.

Supervisor and worker options

In the example above, we defined specs for workers and supervisors. These specs (both for workers as well as supervisors) accept the following options:

  • :id - a name used to identify the child specification internally by the supervisor; defaults to the given module name for the child worker/supervisor

  • :function - the function to invoke on the child to start it

  • :restart - an atom that defines when a terminated child process should be restarted (see the "Restart values" section below)

  • :shutdown - an atom that defines how a child process should be terminated (see the "Shutdown values" section below)

  • :modules - it should be a list with one element [module], where module is the name of the callback module only if the child process is a Supervisor or GenServer; if the child process is a GenEvent, :modules should be :dynamic

Restart values (:restart)

The following restart values are supported in the :restart option:

  • :permanent - the child process is always restarted

  • :temporary - the child process is never restarted (not even when the supervisor's strategy is :rest_for_one or :one_for_all)

  • :transient - the child process is restarted only if it terminates abnormally, i.e., with an exit reason other than :normal, :shutdown or {:shutdown, term}

Note that supervisor that reached maximum restart intensity will exit with :shutdown reason. In this case the supervisor will only restart if its child specification was defined with the :restart option set to :permanent (the default).

Shutdown values (:shutdown)

The following shutdown values are supported in the :shutdown option:

  • :brutal_kill - the child process is unconditionally terminated using Process.exit(child, :kill)

  • :infinity - if the child process is a supervisor, this is a mechanism to give the subtree enough time to shut down; it can also be used with workers with care

  • a non-negative integer - the amount of time in milliseconds that the supervisor tells the child process to terminate by calling Process.exit(child, :shutdown) and then waits for an exit signal back. If no exit signal is received within the specified time, the child process is unconditionally terminated using Process.exit(child, :kill)

Link to this section Summary

Types

Supported ID values

Supported module values

Supported restart values

Supported shutdown values

The supervisor specification

Supported strategies

Supported worker values

Functions

Receives a list of children (workers or supervisors) to supervise and a set of options.

Defines the given module as a supervisor which will be started with the given arguments.

Defines the given module as a worker which will be started with the given arguments.

Link to this section Types

Specs

child_id() :: term()

Supported ID values

Specs

modules() :: :dynamic | [module()]

Supported module values

Specs

restart() :: :permanent | :transient | :temporary

Supported restart values

Specs

shutdown() :: timeout() | :brutal_kill

Supported shutdown values

Specs

spec() ::
  {child_id(), start_fun :: {module(), atom(), [term()]}, restart(), shutdown(),
   worker(), modules()}

The supervisor specification

Specs

strategy() :: :simple_one_for_one | :one_for_one | :one_for_all | :rest_for_one

Supported strategies

Specs

worker() :: :worker | :supervisor

Supported worker values

Link to this section Functions

Link to this function

supervise(children, options)

View Source
This function is deprecated. Use the new child specifications outlined in the Supervisor module instead.

Specs

supervise([spec()],
  strategy: strategy(),
  max_restarts: non_neg_integer(),
  max_seconds: pos_integer()
) :: {:ok, tuple()}

Receives a list of children (workers or supervisors) to supervise and a set of options.

Returns a tuple containing the supervisor specification. This tuple can be used as the return value of the Supervisor.init/1 callback when implementing a module-based supervisor.

Examples

supervise(children, strategy: :one_for_one)

Options

  • :strategy - the restart strategy option. It can be either :one_for_one, :rest_for_one, :one_for_all, or :simple_one_for_one. You can learn more about strategies in the Supervisor module docs.

  • :max_restarts - the maximum number of restarts allowed in a time frame. Defaults to 3.

  • :max_seconds - the time frame in which :max_restarts applies. Defaults to 5.

The :strategy option is required and by default a maximum of 3 restarts is allowed within 5 seconds. Check the Supervisor module for a detailed description of the available strategies.

Link to this function

supervisor(module, args, options \\ [])

View Source
This function is deprecated. Use the new child specifications outlined in the Supervisor module instead.

Specs

supervisor(module(), [term()],
  restart: restart(),
  shutdown: shutdown(),
  id: term(),
  function: atom(),
  modules: modules()
) :: spec()

Defines the given module as a supervisor which will be started with the given arguments.

supervisor(module, [], restart: :permanent)

By default, the function start_link is invoked on the given module. Overall, the default values for the options are:

[
  id: module,
  function: :start_link,
  restart: :permanent,
  shutdown: :infinity,
  modules: [module]
]

See the "Supervisor and worker options" section in the Supervisor.Spec module for more information on the available options.

Link to this function

worker(module, args, options \\ [])

View Source
This function is deprecated. Use the new child specifications outlined in the Supervisor module instead.

Specs

worker(module(), [term()],
  restart: restart(),
  shutdown: shutdown(),
  id: term(),
  function: atom(),
  modules: modules()
) :: spec()

Defines the given module as a worker which will be started with the given arguments.

worker(ExUnit.Runner, [], restart: :permanent)

By default, the function start_link is invoked on the given module. Overall, the default values for the options are:

[
  id: module,
  function: :start_link,
  restart: :permanent,
  shutdown: 5000,
  modules: [module]
]

See the "Supervisor and worker options" section in the Supervisor.Spec module for more information on the available options.