# `Raxol.Gateway.Supervisor`
[🔗](https://github.com/DROOdotFOO/raxol/blob/raxol_gateway-v0.2.0/lib/raxol/gateway/supervisor.ex#L1)

The gateway daemon: pairing, a session `DynamicSupervisor`, and the router.

Strategy is `:rest_for_one`, so the router (which references the sessions
supervisor) restarts if that supervisor dies.

## Options

  * `:handler` (required) -- `{module, opts}` the sessions run. The
    supervisor does not start when the module cannot be loaded (see
    `SessionRouter`)
  * `:adapter` / `:deliver` -- how outbound is delivered (see `SessionRouter`)
  * `:router_name` -- the router's registered name (default
    `Raxol.Gateway.SessionRouter`)
  * `:pairing_name` -- the pairing server's name (default
    `Raxol.Gateway.Pairing`)
  * `:sessions_sup` -- the session supervisor's name (default
    `Raxol.Gateway.SessionSup`)
  * `:authorize` -- `(Route.t() -> :allow | :deny)` the router consults before
    starting a session or delivering an event (see `SessionRouter`). Unset
    allows everything.
  * `:router` / `:pairing` -- extra opts merged into those children

`:rest_for_one` also means a Pairing crash restarts the sessions and the
router behind it. That is deliberate: sessions authorized under the pre-crash
posture should not outlive it. (The router's `:authorize` closure captures a
NAME, so it would survive on its own -- the restart is about the sessions.)
Pass the posture as `:pairing` seed opts rather than calling the running
server, so the restart rebuilds it -- see `Raxol.Gateway.Pairing`.

The corollary is that Pairing sits on the hot path of every event with the
blast radius of every session behind it, so it must not crash on wire input.
`authorize/2` fails closed on a malformed route rather than raising.

# `child_spec`

Returns a specification to start this module under a supervisor.

See `Supervisor`.

# `start_link`

```elixir
@spec start_link(keyword()) :: Supervisor.on_start()
```

---

*Consult [api-reference.md](api-reference.md) for complete listing*