Cafex

Cafex is a pure Elixir implementation of Kafka client with ZooKeeper and Consul intergration.

Cafex support Kafka 0.8 and 0.9 group membership APIs.

Cafex provides all kafka APIs encapsulation, producer implementation and high-level consumer implementation.

Producer

Example

iex> Application.start :cafex
iex> topic_name = "test_topic"
iex> brokers = [{"127.0.0.1", 9092}]
iex> {:ok, producer} = Cafex.start_producer topic_name, client_id: "myproducer",
                                                        brokers: brokers,
                                                        partitioner: MyPartitioner,
                                                        acks: 1,
                                                        batch_num: 100,
                                                        linger_ms: 10
iex> Cafex.produce producer, "message", key: "key"
iex> Cafex.async_produce producer, "message", key: "key"

Producer options

partitioner

The partitioner for partitioning messages amongst sub-topics. The default partitioner is Cafex.Partitioner.Random.

client_id

The client id is a user-specified string sent in each request to help trace calls. It should logically identify the application making the request.

Default cafex_producer.

acks

The number of acknowledgments the producer requires the leader to have received before considering a request complete. This controls the durability of records that are sent.

Default value is 1.

batch_num

The number of messages to send in one batch when linger_ms is not zero. The producer will wait until either this number of messages are ready to send.

linger_ms

This setting is the same as linger.ms config in the new official producer configs. This setting defaults to 0 (i.e. no delay).

NOTE: If linger_ms is set to 0, the batch_num will not take effect.

Consumer

Example

defmodule MyConsumer do
  use Cafex.Consumer

  def consume(msg, state) do
    # handle the msg
    {:ok, state}
  end
end

iex> Application.start :cafex
iex> topic_name = "test_topic"
iex> brokers = [{"127.0.0.1", 9092}]
iex> options = [client_id: "myconsumer",
                topic: topic_name,
                brokers: brokers,
                offset_storage: :kafka,
                group_manager: :kafka,
                lock: :consul,
                group_session_timeout: 7000, # ms
                auto_commit: true,
                auto_commit_interval: 500,   # ms
                auto_commit_max_buffers: 50,
                fetch_wait_time: 100,        # ms
                fetch_min_bytes: 32 * 1024,
                fetch_max_bytes: 64 * 1024,
                handler: {MyConsumer, []}]
iex> {:ok, consumer} = Cafex.start_consumer :myconsumer, options

The options argument of the function start_consumer can be put in the config/config.exs:

config :cafex, :myconsumer,
  client_id: "cafex",
  topic: "test_topic",
  brokers: [
    {"192.168.99.100", 9092},
    {"192.168.99.101", 9092}
  ],
  offset_storage: :kafka,
  group_manager: :kafka,
  lock: :consul,
  group_session_timeout: 7000, # ms
  auto_commit: true,
  auto_commit_interval: 500,   # ms
  auto_commit_max_buffers: 50,
  fetch_wait_time: 100,        # ms
  fetch_min_bytes: 32 * 1024,
  fetch_max_bytes: 64 * 1024,
  handler: {MyConsumer, []}

By default, cafex will use :kafka as the offset storage, use the new kafka group membership API, which was added in the 0.9.x, as the group manager, and use the :consul as the worker lock. Make suer your Kafka server is 0.9.x or above.

But :zookeeper is another option for these. If you use zookeeper, the starting options of :erlzk must be specified under the :zookeeper key:

config :cafex, :myconsumer,
  client_id: "cafex",
  topic: "test_topic",
  brokers: [...],
  offset_storage: :zookeeper,
  group_manager: :zookeeper,
  lock: :zookeeper,
  zookeeper: [
    timeout: 5000,
    servers: [{"192.168.99.100", 2181}],
    chroot: "/cafex"
  ],
  ...

TODO

• Support kafka 0.10.x.x
• Add tests