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https://github.com/MyMedsAndMe/spell

Spell is a Web Application Messaging Protocol (WAMP) client implementation in Elixir. WAMP is an open standard WebSocket subprotocol that provides two application messaging patterns in one unified protocol: Remote Procedure Calls + Publish & Subscribe: http://wamp.ws/
https://github.com/MyMedsAndMe/spell

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Spell is a Web Application Messaging Protocol (WAMP) client implementation in Elixir. WAMP is an open standard WebSocket subprotocol that provides two application messaging patterns in one unified protocol: Remote Procedure Calls + Publish & Subscribe: http://wamp.ws/

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README 

        
# spell [DEPRECATED]



Spell is an [Elixir](http://elixir-lang.org/) [WAMP](http://wamp.ws/) client

implementing the

[basic profile](https://github.com/tavendo/WAMP/blob/master/spec/basic.md)

specification.



# Reason for fork



For spellchecking old symposium



# Oficial readme



Why WAMP?



[WAMP](http://wamp.ws/) is the Web Application Message Protocol supported by

[Tavendo](http://tavendo.com/). It's an open standard WebSocket subprotocol that

provides two application messaging patterns in one unified protocol: Remote

Procedure Calls + Publish & Subscribe.



Why Spell?



- Flexible interface: one line blocking calls or raw message handling -- use

whichever tool works best.

- Robust peers: peer processes are supervised, and will restart or retry when

appropriate.

- Easy to extend: add new roles, transports, or serializers without changing

the core library:



## Getting Help



Spell uses GitHub [issues](https://github.com/MyMedsAndMe/spell/issues) and

[pull requests](https://github.com/MyMedsAndMe/spell/pulls) for development.



Spell has a mailing list at [email protected]; general questions or ideas are

welcome there. See [librelist](http://librelist.com/) for how to sign up.



## Using Spell with your Elixir Project



To use Spell from within your Elixir library add, add it to your `mix.exs` deps,

along with the required transport and serialization libraries:



```elixir

defp deps do

  [

    ...

    # Required:

    {:spell, "~> 0.1"},

    # Required if using the websocket transport:

    {:websocket_client, github: "jeremyong/websocket_client", tag: "v0.7"},

    # Required if using the JSON serializer:

    {:poison, "~> 1.4"},

    # Required if using the msgpack serializer:

    {:msgpax, "~> 0.7"}

  ]

end

```



Fetch the dependencies by running:



```

$ mix deps.get

```



## How it Works



You can run the examples you're about to run into, though first you'll need

[crossbar.io](http://crossbar.io/). You might install it via pip:



```shell

$ pip install crossbar

```



If you are going to use MessagePack you will need to install the optional

crossbar package.



```shell

$ pip install crossbar[msgpack]

```



Start an Elixir shell:



```bash

$ iex -S mix

```



Start up Crossbar.io:



```elixir

iex> Crossbar.start()

```



To stop Crossbar.io from IEx:



```elixir

iex> Crossbar.stop()

```



You can find more detailed documentation at any time by checking

the source code documentation. `Spell` provides an entry point:



```elixir

iex> h Spell

```



You can hit C-c C-c to exit the shell. Be sure to stop Crossbar.io

first.



### Peers



In WAMP, messages are exchanged between peers. Peers are assigned a set of roles

which define how they handle messages. A client peer (Spell!) may have any

choice of client roles, and a server peer may have any choice of server roles.



There are two functional groupings of roles:



- PubSub

  - Publisher

  - Subscriber

  - Broker _[Server]_

- RPC

  - Caller

  - Callee

  - Dealer _[Server]_



By default a client peer is started with the above four client roles:



```elixir

Spell.connect("ws://example.org", realm: "realm1")

```



See `Spell.Peer` and `Spell.Role`.



#### Authentication



Spell supports

[WAMP Challenge Response Authentication (CRA)](https://github.com/tavendo/WAMP/blob/master/spec/advanced.md#challenge-response-authentication). This

is flexible, and can be used to back a variety of authentication schemes.



To setup a Spell peer with authentication:



```elixir

alias Spell.Authentication.CRA

authentication = [id: "harry", schemes: [{CRA, [secret: "alohamora"]}]]

Spell.connect("ws://example.org", realm: "realm1",

              authentication: authentication)

```



See `Spell.Authentication`.



### PubSub



Once subscribed to a topic, the subscriber will receive all messages

published to that topic.



```elixir

# Events must be published to a topic.

topic = "com.spell.example.pubsub.topic"



# Create a peer with the subscriber role.

subscriber = Spell.connect(Crossbar.uri,

                           realm: Crossbar.get_realm(),

                           roles: [Spell.Role.Subscriber])



# `call_subscribe/2,3` synchronously subscribes to the topic.

{:ok, subscription} = Spell.call_subscribe(subscriber, topic)



# Create a peer with the publisher role.

publisher = Spell.connect(Crossbar.uri,

                          realm: Crossbar.get_realm(),

                          roles: [Spell.Role.Publisher])



# `call_publish/2,3` synchronously publishes a message to the topic.

{:ok, publication} = Spell.call_publish(publisher, topic)



# `receive_event/2,3` blocks to receive the event.

case Spell.receive_event(publisher, subscription) do

  {:ok, event}     -> handle_event(event)

  {:error, reason} -> {:error, reason}

end



# Cleanup.

for peer <- [subscriber, publisher], do: Spell.close(peer)

```



See `Spell.Role.Publisher` and `Spell.Role.Subscriber` for more information.



#### Pattern-based subscriptions



By default, peers subscribe to topics using an exact matching policy. Using

pattern-based subscriptions a peer can receive messages that match certain

criteria.



```elixir

# assuming we have a subscriber peer connected



# exact match

{:ok, subscription} = Spell.call_subscribe(subscriber, "com.spell.my_topic")

# subscriber will receive messages published in the "com.spell.my_topic" topic



# prefix match

{:ok, subscription} = Spell.call_subscribe(subscriber, "com.spell.my_topic_prefix", options: %{match: :prefix})

# subscriber will receive messages published in topics:

# "com.spell.my_topic_prefix.foo",  "com.spell.my_topic_prefix.bar", ...



# wildcard match

{:ok, subscription} = Spell.call_subscribe(subscriber, "com.spell..my_topic", options: %{match: :wildcard})

# subscriber will receive messages published in topics:

# "com.spell.foo.my_topic", "com.spell.bar.my_topic", ...

```



### RPC



RPC allows a caller to call a procedure using a remote callee.



Let's start with the caller's half:



```elixir

# Calls are sent to a particular procedure.

procedure = "com.spell.example.rpc.procedure"



# Create a peer with the callee role.

caller = Spell.connect(Crossbar.uri,

                       realm: Crossbar.get_realm(),

                       roles: [Spell.Role.Callee])



# `call_register/2,3` synchronously calls the procedure with the arguments.

{:ok, registration} = Spell.call(subscriber, procedure,

                                 arguments: ["args"],

                                 arguments_kw: %{})



Spell.close(caller)

```



In addition to the synchronous `Spell.call_...` type functions described so far,

Spell includes asynchronous `Spell.cast_...` functions. To handle the result of

these messages you can use a `Spell.receive_...` helper, or, most flexibly,

use a `receive` clause.



Next is a contrived example showing the RPC caller and the callee being used

from a single process. Note how asynchronous casts and receive functions are

used to avoid a deadlock.



Note: I omitted the `arguments` and `arguments_kw` options for brevity's sake.



```elixir

# Calls are sent to a particular procedure.

procedure = "com.spell.example.rpc.procedure"



# Create a peer with the callee role.

callee = Spell.connect(Crossbar.uri,

                       realm: Crossbar.get_realm(),

                       roles: [Spell.Role.Callee])



# `call_register/2,3` synchronously registers the procedure.

{:ok, registration} = Spell.call_register(callee, procedure)



# Create a peer with the caller role.

caller = Spell.connect(Crossbar.uri,

                       realm: Crossbar.get_realm(),

                       roles: [Spell.Role.Caller])



# `cast_call/2,3` asynchronously calls the procedure.

{:ok, call} = Spell.cast_call(caller, procedure)



# `receive_invocation/2,3` blocks until it receives the call invocation.

{:ok, invocation} = Spell.receive_invocation(callee, call)



# `cast_yield/2,3` asynchronously yields the result back to the caller

:ok = Spell.cast_yield(callee, invocation.id, handle_invocation(invocation))



# `receive_event/2,3` blocks until timeout to receive the result.

case Spell.receive_result(publisher, call) do

  {:ok, result}    -> handle_result(result)

  {:error, reason} -> {:error, reason}

end



# Cleanup.

for peer <- [callee, caller], do: Spell.close(peer)

```



See `Spell.Role.Caller` and `Spell.Role.Callee` for more information.



### Adding New Roles



In Spell, Roles are middleware for handling messages. Technically they're most

similar to GenEvent handlers: callbacks which are hooked into a manager. In this

case, the manager is a `Spell.Peer` process.



It's easy to get started:



```elixir

defmodule Broker do

  use Spell.Role



  def get_features(_options), do: {:broker, %{}}



  def handle_message(%Message{type: :publish} = message, peer, state) do

    publish(message, peer, state)

  end



  ... shamelessly skipping the real work.

end



Spell.Peer.connect(Crossbar.uri, realm: Crossbar.get_realm(), roles: [Broker])

```



See `Spell.Role` for descriptions of the Role callbacks.



## Examples



Look in `examples/` for the scripts.



There are shortcuts to run the examples -- run the following from Spell's root:



```shell

$ mix spell.example.pubsub

```



## Testing



To run Spell's integration tests, you must have

[crossbar installed](#crossbar-install).



To run the tests:



```shell

# run unit and integration tests with default configuration

$ mix test



# run only unit tests

$ mix test.unit



# run integration tests using a specific serializer

$ SERIALIZER=json mix test.integration

$ SERIALIZER=msgpack mix test.integration



# run integration tests with all possible serializers

$ SERIALIZER=all mix test.integration

$ mix test.integration



# run unit and integration tests with all possible configurations

$ mix test.all

```



The Crossbar.io test server can be configured to listen on a different port

by running:



```shell

$ CROSSBAR_PORT=8000 mix ...

```



## Creating the Documentation



To generate HTML from the source code documentation you can run:



```shell

$ mix docs

```