Fails to start on fresh installation

[timwis]

Hello, I'm new to elixir but learning quickly. I followed the installation instructions to the letter, but I can't start my application once I append {DataDigestQueue.Broker, []} to the children list in lib/data_digest/application.ex.

The error message when I run mix phx.server is:

** (Mix) Could not start application data_digest: DataDigest.Application.start(:normal, []) returned an error: shutdown: failed to start child: DataDigestQueue.Broker
    ** (EXIT) shutdown: failed to start child: ConduitAMQP
        ** (EXIT) an exception was raised:
            ** (UndefinedFunctionError) function ConduitAMQP.start_link/1 is undefined or private
                (conduit_amqp) ConduitAMQP.start_link([DataDigestQueue.Broker, [{:queue, "data_digest.jobs", []}], %{jobs: [from: "data_digest.jobs"]}, [adapter: ConduitAMQP, url: "amqp://guest:guest@localhost:5672"]])
                (stdlib) supervisor.erl:379: :supervisor.do_start_child_i/3
                (stdlib) supervisor.erl:365: :supervisor.do_start_child/2
                (stdlib) supervisor.erl:349: anonymous fn/3 in :supervisor.start_children/2
                (stdlib) supervisor.erl:1157: :supervisor.children_map/4
                (stdlib) supervisor.erl:315: :supervisor.init_children/2
                (stdlib) gen_server.erl:374: :gen_server.init_it/2
                (stdlib) gen_server.erl:342: :gen_server.init_it/6
                (stdlib) proc_lib.erl:249: :proc_lib.init_p_do_apply/3

That suggests to me that Conduit.Broker is trying to start ConduitAMQP with the wrong number of arguments (1 keyword list instead of it spread out among 4 arguments). I can see where this is likely happening in the library, but am surprised that I don't see any other reports of this issue so I assume it's user error after all.

• Conduit.Broker tries to start the adapter with one arg
• ConduitAMQP expects four args (though so does ConduitSQS)

In the meantime, I'm able to get it work by modifying deps/conduit_amqp/lib/conduit_amqp.ex to add:

  def start_link([broker, topology, subscribers, opts]) do
    start_link(broker, topology, subscribers, opts)
  end

[blatyo]

What version of Elixir, conduit, and conduit_amqp are you using?
Can you share your application.ex start function?

https://github.com/conduitframework/conduit/blob/95c67209aa/lib/conduit/broker.ex#L83

This get's passed to child_spec/2 on the adapter module, not directly to start_link.

https://github.com/conduitframework/conduit_amqp/blob/master/lib/conduit_amqp.ex#L31-L37

The list of arguments here, are individual arguments. So a list of 4, is equivalent to four arguments.

[timwis]

I'm on elixir v1.8.1, conduit ~> 0.12, conduit_amqp ~> 0.4.

  def start(_type, _args) do
    # List all child processes to be supervised
    children = [
      # Start the Ecto repository
      DataDigest.Repo,
      # Start the endpoint when the application starts
      DataDigestWeb.Endpoint,
      # Starts a worker by calling: DataDigest.Worker.start_link(arg)
      # {DataDigest.Worker, arg},
      {DataDigestQueue.Broker, []}
    ]

    # See https://hexdocs.pm/elixir/Supervisor.html
    # for other strategies and supported options
    opts = [strategy: :one_for_one, name: DataDigest.Supervisor]
    Supervisor.start_link(children, opts)
  end

[blatyo]

Can you provide the specific versions your using: mix deps

[blatyo]

I suspect the version of conduit and conduit_amqp you're using are not compatible with each other. Newest version of conduit is 0.12.10 and newest of conduit_amqp is 0.6.3. If something said you should use ~> 0.4, that should get updated.

[blatyo]

Also, worth noting that there is an example app you can compare against: https://github.com/conduitframework/conduit_amqp_example

[timwis]

Sure, mix.deps says conduit 0.12.10 and conduit_amqp 0.4.6. I was following the generator output. Upgrading to 0.6.3 has fixed it. Thanks! (And yes I went through the example before reporting the issue, thanks though)