# `Chronicle.Client`
[🔗](https://github.com/Cratis/Chronicle.Elixir/blob/main/lib/chronicle/client.ex#L4)

Supervisor that manages a Chronicle connection and all registered observers.

`Chronicle.Client` is the main entry point for the Chronicle Elixir client.
Start it in your application's supervision tree, providing a connection
string and the list of event types, reactors, reducers, and read models to
register.

## Usage

In your `Application.start/2`:

    def start(_type, _args) do
      children = [
        {Chronicle.Client,
          connection_string: "chronicle://localhost:35000?disableTls=true",
          event_store: "my-store",
          event_types: [
            MyApp.Events.AccountOpened,
            MyApp.Events.FundsDeposited
          ],
          reactors: [MyApp.Reactors.NotificationReactor],
          reducers: [MyApp.Reducers.AccountReducer],
          read_models: [MyApp.ReadModels.Account]}
      ]

      Supervisor.start_link(children, strategy: :one_for_one)
    end

Read models that contain `from/2`, `join/2`, or `removed_with/2` declarations
are automatically registered as server-side projections.

## Multiple clients

You can start multiple clients with different names:

    {Chronicle.Client,
      name: :bank_chronicle,
      connection_string: "chronicle://bank-server:35000",
      event_store: "bank"}

    {Chronicle.Client,
      name: :crm_chronicle,
      connection_string: "chronicle://crm-server:35000",
      event_store: "crm"}

## Options

  * `:name` — registered name for this client. Defaults to `Chronicle.Client`.
  * `:connection_string` — a connection string binary or
    `Chronicle.Connections.ConnectionString` struct. Defaults to
    `ConnectionString.default/0` (localhost:35000).
  * `:event_store` — the event store name. Defaults to `"default"`.
  * `:namespace` — the namespace within the event store. Defaults to `"default"`.
  * `:event_types` — list of event type modules to register with the event store.
  * `:reactors` — list of reactor modules to start (each `use Chronicle.Reactor`).
  * `:reducers` — list of reducer modules to start (each `use Chronicle.Reducer`).
  * `:read_models` — list of read model modules (each `use Chronicle.ReadModel`).
    Modules that contain `from/2` declarations are registered as projections.

## Convenience functions

Once started, use `Chronicle.append/3` and `Chronicle.read_model/3` for the
most common operations, or use the subsystem modules directly:

  * `Chronicle.EventLog` — append and query events
  * `Chronicle.ReadModels` — query read model instances
  * `Chronicle.EventTypes` — manage event type registrations

# `child_spec`

Returns a specification to start this module under a supervisor.

See `Supervisor`.

# `config`

```elixir
@spec config(atom() | pid()) :: map()
```

Returns the stored configuration for the given client name.

Used internally by `Chronicle.EventLog`, `Chronicle.ReadModels`, etc.

# `start_link`

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

Starts a Chronicle client supervisor linked to the current process.

---

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