OffBroadwayRedisStream

A Redis Stream consumer for Broadway.

Broadway producer acts as a consumer in the specified Redis stream consumer group. You can run multiple consumers to get better throughput and fault tolerance. Please check Redis Stream Intro for details on stream data type.

It supports failover by automatically claiming pending messages when a node dies. A node is considered dead when it fails to send heartbeats.

defmodule MyBroadway do
  use Broadway

  def start_link(_opts) do
    Broadway.start_link(__MODULE__,
      name: __MODULE__,
      producer: [
        module:
          {OffBroadwayRedisStream.Producer,
           [
             redis_client_opts: [host: "localhost"],
             stream: "orders",
             group: "processor-group",
             consumer_name: hostname()
           ]}
      ],
      processors: [
        default: [min_demand: 5, max_demand: 1000]
      ]
    )
  end

  def handle_message(_, message, _) do
    [_id, key_value_list] = message.data
    IO.inspect(key_value_list, label: "Got message")
    message
  end

  @max_attempts 5

  def handle_failed(messages, _) do
    for message <- messages do
      if message.metadata.attempt < @max_attempts do
        Broadway.Message.configure_ack(message, retry: true)
      else
        [id, _] = message.data
        IO.inspect(id, label: "Dropping")
      end
    end
  end

  defp hostname do
    {:ok, host} = :inet.gethostname()
    to_string(host)
  end
end

Currently, it only supports Redis 6.0.2 and above.

Installation

def deps do
  [
    {:off_broadway_redis_stream, "~> x.x.x"}
  ]
end

License

Copyright (c) 2021 Akash Hiremath.

OffBroadwayRedisStream source code is released under Apache License 2.0. Check LICENSE for more information.