Supervisor.Spec — Elixir v1.16.3

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# View Source Supervisor.Spec (Elixir v1.16.3)

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Outdated functions for building child specifications.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)`

# Summary

## Types

child_id()

Supported ID values

modules()

Supported module values

restart()

Supported restart values

shutdown()

Supported shutdown values

spec()

The supervisor specification

strategy()

Supported strategies

worker()

Supported worker values

## Functions

supervise(children, options) deprecated

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

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

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

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

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

# Types

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# child_id()

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    @type child_id() :: term()

Supported ID values

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# modules()

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

Supported module values

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# restart()

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

Supported restart values

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# shutdown()

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    @type shutdown() :: timeout() | :brutal_kill

Supported shutdown values

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# spec()

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

The supervisor specification

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# strategy()

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

Supported strategies

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# worker()

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    @type worker() :: :worker | :supervisor

Supported worker values

# Functions

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# supervise(children, options)

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

    @spec 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.

    @spec 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.

    @spec 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.