AMQP RPC Client/Server templates

Warning! POC quality!

Goals

• Reduce boilerplate
• Handle reconnects
• Messages housekeeping
• Logging
• Monitoring
• Use fuse
• Content negotiation

Fuse

Fuse helps reduce latency when something goes wrong with RabbitMQ or RPC server side by breaking circuit and returning immideately. Fuse can be configured via fuse_name and fuse_opts keys. We trying to maintain sensible default for those.

Monitoring/Instrumenting

Clients can be instrumented using built-in metrics plugins. Currenly implemented

• ETS-backed plugin (default)
• Prometheus plugin.

Example

Below is ‘classic’ RPC example from RabbitMQ tutorials rewritten using amqp_rpc:

Client:

defmodule Fibonacci do
  use AMQP.RPC.Client, [exchange: "",
                        queue: "rpc_queue"]

  def fib(n, timeout \\ @timeout) do
    rpc(%{command_name: "fib",
          args: n}, timeout)
  end
end

Server:

defmodule FibonacciServer do
  use AMQP.RPC.Server, [exchange: "",
                        queue: "rpc_queue",
                        commands: [:fib]]

  ## adapted from https://gist.github.com/stevedowney/2f910bd3d72678b4cf99

  def fib(0), do: 0

  def fib(n)
  when is_number(n) and n > 0,
    do: fib(n, 1, 0, 1)

  def fib(_), do: [error: "positive integers only"]

  def fib(n, m, _prev_fib, current_fib)
  when n == m,
    do: current_fib

  def fib(n, m, prev_fib, current_fib),
    do: fib(n, m+1, current_fib, prev_fib + current_fib)

end

Installation

Available in Hex, the package can be installed as:

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

```elixir
def deps do
  [{:amqp_rpc, "~> 0.0.7"}]
end
```

1. Ensure amqp_rpc is started before your application:

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