ConduitNSQ

A NSQ adapter for conduit.

CAVEAT: This adapter library is not mature so take precaution when using it for production. This library also may not be as lightweight, eficient, thoughtout. As an example, this library uses honeydew as a worker pool to throttle sending and receiving messages instead of the builtin GenStage.

Installation

The package can be installed by adding conduit_nsq to your list of dependencies in mix.exs:

def deps do
  [{:conduit_nsq, "~> 0.1.4"}]
end

Once you created your own MyApp.Broker, remember to add it in your application:

  def start(_type, _args) do
    children = [
      MyApp.Broker
    ]

    opts = [strategy: :one_for_one, name: MyApp.Supervisor]
    Supervisor.start_link(children, opts)
  end

Configuring the Adapter

This library uses elixir_nsq to connect to the message queue. Aside from specifiying the :adapter, every option in the following snippet below is passed down to NSQ.Config:

config :my_app, MyApp.Broker,
  adapter: ConduitNSQ,
  producer_nsqds: [
    "127.0.0.1:12150",
  ],
  nsqds: [
    "127.0.0.1:12150",
    "127.0.0.1:13150",
    "127.0.0.1:14150"
  ],
  nsqlookupds: ["127.0.0.1:12161"],

  backoff_multiplier: 2_000

Checkout the list of supported options.

The only different option is :producer_nsqds which is publisher specific endpoints than consumer specific endpoints. This option is to support the idiomatic strategy of publishing to colocated nsqds while listening in to external producers. (See Eliminating SPOFs).

For more adapter specific options:

# Default config
config :conduit_nsq,
  publisher_workers: 3,
  processor_workers: 10,
  publish_timeout: 60_000,
  process_timeout: 60_000

Options

Aside from `:adapter`, the current options should be good defaults.

• :adapter - The message queue adapter to use, should be ConduitNSQ.
• :publisher_workers - The number of workers for publishing messages. See Honeydew.start_workers/3
• :processor_workers - The number of workers for receiving messages. See Honeydew.start_workers/3
• :publish_timeout - Timeout in publishing messages. See Honeydew.yield/2
• :process_timeout - Timeout in receiving messages. See Honeydew.yield/2

Configuring Topic

Inside the configure block of a broker, you can define topics via queue that will be created at application startup with the options you specify.

defmodule MyApp.Broker do
  configure do
    queue "my-topic"
    queue "other-topic"
  end
end

All topics that the application will publish to must be defined here since each message is routed to the corresponding NSQ.Producer.Supervisor otherwise the message might be unsent.

Ephemeral Topics or Channels

You can suffix topics and channels with #ephemeral based on bounded memory footprint). However, when publishing or subscribing to the topic, also add the same suffix to the topic or channel to match

Configuring a Subscriber

Inside an incoming block for a broker, you can define subscriptions to topics. Conduit will route messages on those topics to your subscribers.

defmodule MyApp.Broker do
  incoming MyApp do
    subscribe :my_subscriber, MySubscriber,
      topic: "my-queue",
      channel: "my-channel"
    subscribe :my_other_subscriber, MyOtherSubscriber,
      topic: "my-other-queue",
      from: "my-other-channel"
  end
end

Make sure the :topics here are found in the configure block to receive the messages.

Options

The only required options are :topic and :channel which follows NSQ.Consumer.Supervisor.

• :topic - Topic to connect with
• :channel - Topic channel to listen into

Configuring a Publisher

Inside an outgoing block for a broker, you can define publications to topics.

defmodule MyApp.Broker do
  outgoing do
    publish :something, topic: "my-topic"
    publish :something_else, topic: "my-other-topic",
  end
end

Options

The only required option is :topic which follows NSQ.Producer.Supervisor.

• :topic - Topic to publish to