Elixir v1.4.5 Supervisor.Spec View Source
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
Notice in this case we don’t have to explicitly import
Supervisor.Spec
as use Supervisor
automatically does so.
Defining a module-based supervisor can be useful, for example,
to perform initialization tasks in the c: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 aSupervisor
orGenServer
; if the child process is aGenEvent
,: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}
Shutdown values (:shutdown)
The following shutdown values are supported in the :shutdown
option:
:brutal_kill
- the child process is unconditionally terminated usingProcess.exit(child, :kill)
:infinity
- if the child process is a supervisor, this is a mechanism to give the subtree enough time to shutdown; it can also be used with workers with careany integer - the value of
:shutdown
can also be any integer meaning that the supervisor tells the child process to terminate by callingProcess.exit(child, :shutdown)
and then waits for an exit signal back. If no exit signal is received within the specified time (the value of this option, in milliseconds), the child process is unconditionally terminated usingProcess.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
Supported id values
Supported module values
Supported restart values
Supported shutdown values
The supervisor specification
strategy :: :simple_one_for_one | :one_for_one | :one_for_all | :rest_for_one
Supported strategies
Supported worker values
Link to this section Functions
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 c: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 theSupervisor
module docs.:max_restarts
- the maximum amount of restarts allowed in a time frame. Defaults to3
.:max_seconds
- the time frame in which:max_restarts
applies. Defaults to5
.
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.
Defines the given module
as a supervisor which will be started
with the given arguments.
supervisor(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: :infinity,
modules: [module]]
Check the documentation for the Supervisor.Spec
module for more
information on the options.
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]]
Check the documentation for the Supervisor.Spec
module for more
information on the options.