Gnat

Connect to and interact with NATS and/or NATS Streaming servers.

Installation

If available in Hex, the package can be installed as:

1. Add gnat to your list of dependencies in mix.exs:

```elixir
def deps do
  [{:gnat, "~> 0.1.0"}]
end
```

2. Ensure gnat is started before your application:

```elixir
def application do
  [applications: [:gnat]]
end
```

Features

• Documentation
  • NATS
  • NATS Streaming
• NATS Streaming
• Request/reply API

Server Version Requirements

• NATS >= 0.9.0 (I think)
• NATS Streaming >= 0.3.7

Quickstart - NATS

{:ok, conn} = Gnat.start_link(deliver_to: self())
Gnat.sub(conn, "foo", "sid123")
Gnat.pub(conn, "foo", "hello!")
receive do
  {:nats_msg, msg} -> IO.puts "#{msg.subject}: #{msg.payload}"
end
Gnat.close(conn)

Quickstart - NATS Streaming

{:ok, conn} = Gnat.Stream.start_link(deliver_to: self())
Gnat.Stream.subscribe(conn, "foo")
Gnat.Stream.publish(conn, "foo", "hello!")
receive do
  {:nats_stream_msg, msg} ->
    IO.puts "#{msg.subject}: #{msg.data}"
    Gnat.Stream.ack(conn, msg)
end
Gnat.Stream.close(conn)

Request/Reply

The NATS protocol allows for request/reply messaging.

Gnat makes this very easy to use with Gnat.request/3. We can demonstrate by writing a echo server.

Server

{:ok, conn} = Gnat.start_link(deliver_to: self())
Gnat.sub(conn, "echo", Gnat.new_sid)
Stream.repeatedly(fn ->
  receive do
    {:nats_msg, msg} -> msg
  end
end) |> Enum.each(fn msg ->
  Gnat.pub(conn, msg.reply_to, msg.payload)
end)

Client

{:ok, conn} = Gnat.start_link
{:ok, reply} = Gnat.request(conn, "echo", "hello")
IO.puts reply.payload # => "hello"
{:ok, res} = Gnat.request(conn, "echo", "goodbye")
IO.puts reply.payload # => "goodbye"
Gnat.close(conn)

TODO

• Authentication
• one-to-many request/reply