Embedded mode
=============
Purpose
-------
Embedded mode allows you to insert Ranch listeners directly
in your supervision tree. This allows for greater fault tolerance
control by permitting the shutdown of a listener due to the
failure of another part of the application and vice versa.
Embedding
---------
To embed Ranch in your application you can simply add the child specs
to your supervision tree. This can all be done in the ```init/1``` function
of one of your application supervisors.
Ranch requires at the minimum two kinds of child specs for embedding.
First, you need to add ```ranch_sup``` to your supervision tree, only once,
regardless of the number of listeners you will use. Then you need to
add the child specs for each listener.
Ranch has a convenience function for getting the listeners child specs
called ```ranch:child_spec/6```, that works like ```ranch:start_listener/6```,
except that it doesn't start anything, it only returns child specs.
As for ```ranch_sup```, the child spec is simple enough to not require a
convenience function.
The following example adds both ```ranch_sup``` and one listener to another
application's supervision tree.
``` erlang
init([]) ->
RanchSupSpec = {ranch_sup, {ranch_sup, start_link, []},
permanent, 5000, supervisor, [ranch_sup]},
ListenerSpec = ranch:child_spec(echo, 100,
ranch_tcp, [{port, 5555}],
echo_protocol, []
),
{ok, {{one_for_one, 10, 10}, [RanchSupSpec, ListenerSpec]}}.
```
Remember, you can add as many listener child specs as needed, but only
one ```ranch_sup``` spec!
It is recommended that your architecture makes sure that all listeners
are restarted if ```ranch_sup``` fails. See the Ranch internals chapter for
more details on how Ranch does it.
