DQ - Durable Queue

A library for using durable message queues like SQS or Postgres by way of Ecto.

It also has a testing adapter which allows you to run test synchronously.

TODO

• process that polls for jobs that have timed out and restarts them

Installation

If available in Hex, the package can be installed by adding que to your list of dependencies in mix.exs:

def deps do
  [{:dq, "~> 0.1.0"}]
end

# lib/queue.ex
defmodule Queue do
  use DQ.Queue, otp_app: :example
end

# lib/pool.ex
defmodule Pool do
  use DQ.Pool, otp_app: :example
end

# start the DQ server to run a consumer
worker(Pool, []),

# config.exs
config :example, Pool,
   producers: 1,
   queues: [Queue],
   min_demand: 1,
   max_demand: 10,
   after_empty_result_ms: 1000

# admin ui auth token
config :dq, :token, "xxx"

Ecto (Postgres)

Allows you to create a queue based on a postgres table

Config

config :example, Queue,
  adapter: DQ.Adapters.Ecto,
  repo: Simple.Repo,
  table: "job_table_name"

Migration

defmodule Repo.Migrations.CreateYourJobsTable do
  use Ecto.Migration

  def change do
    create table(:job_table_name) do
      DQ.Adapters.Ecto.Migrations.job()
    end
    DQ.Adapters.Ecto.Migrations.indexes(:job_table_name)
  end
end

Schema

This is is optional, but it allows you to a jobs table on a per struct basis.

defmodule YourJobSchema do
  use Ecto.Schema
  import DQ.Adapters.Ecto.Schema

  schema "job_table_name" do
    job()
  end
end

SQS

config :example, Queue,
  adapter: DQ.Adapters.Sqs
  queue_name: "sqs_queue_name",
  dead_queue_name: "sqs_queue_name_error",

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/dq.

Dead Queues

config :example, Queue,
  dead_queue: DeadQueue

Admin Interface

http://dq-admin.s3-website-us-east-1.amazonaws.com

API Config

Inside of a phoenix project

pipeline :dq do
  plug :accepts, ["json"]
  plug DQ.Plug
end

scope "/dq", DQ do
  pipe_through :dq
  forward "/", Plug.Router, :index
end

config :dq, :queues, [Queue]
config :dq, :token, "generate a long token here"

TODO

• remove genstage, just use simple poller/pool
• single job schema, possible ecto_poly ussage for job structs