To use HareMq in your Elixir project, follow these steps:

Install the required dependencies by adding them to your mix.exs file:

defp deps do
[
  {:hare_mq, "~> 1.2.0"}
]
end

Publisher

The MyApp.MessageProducer module is responsible for publishing messages to a message queue using the HareMq.Publisher behavior. This module provides an interface for sending messages with specified routing and exchange settings. It also supports deduplication based on specific keys.

The MyApp.MessageProducer module is configured with the following options:

• routing_key: Specifies the routing key used to route messages to the appropriate queue. In this example, the routing key is set to "routing_key".

• exchange: Defines the exchange to which messages will be published. In this example, the exchange is set to "exchange".

• unique: This configuration option sets up deduplication rules:

• period: Defines the time period for deduplication in ms. In this example, it is set to :infinity, meaning that messages are considered unique indefinitely based on the specified keys.

• keys: A list of keys used to determine message uniqueness. If the message is a string, deduplication is managed by default behavior and you do not need to specify keys. If provided, deduplication is based on the specified keys. In the example, deduplication is based on the :project_id key.

defmodule MyApp.MessageProducer do
use HareMq.Publisher,
  routing_key: "routing_key",
  exchange: "exchange"

# Function to send a message to the message queue.
def send_message(message) do
  # Publish the message using the HareMq.Publisher behavior.
  publish_message(message)
end
end

defmodule MyApp.MessageProducer do
use HareMq.Publisher,
  routing_key: "routing_key",
  exchange: "exchange",
  unique: [
    period: :infinity,
    keys: [:project_id]
  ]

# Function to send a message to the message queue.
def send_message(message) do
  # Publish the message using the HareMq.Publisher behavior.
  publish_message(message)
end
end

Consumer

The MyApp.MessageConsumer module is designed to consume messages from a message queue using the HareMq.Consumer behavior. This module provides the functionality to receive and process messages with specific routing and exchange settings.

The MyApp.MessageConsumer module is configured with the following options:

• queue_name: Specifies the name of the queue from which messages will be consumed. In this example, the queue name is set to "queue_name".

• routing_key: Defines the routing key used to filter messages. In this example, the routing key is set to "routing_key".

• exchange: Defines the exchange from which messages will be consumed. In this example, the exchange is set to "exchange".

defmodule MyApp.MessageConsumer do
use HareMq.Consumer,
  queue_name: "queue_name",
  routing_key: "routing_key",
  exchange: "exchange"

# Function to process a received message.
def consume(message) do
  # Log the beginning of the message processing.
  IO.puts("Processing message: #{inspect(message)}")
end
end

Dynamic Consumer

The MyApp.MessageConsumer module is designed to consume messages from a message queue using the HareMq.DynamicConsumer behavior. This module provides the functionality to receive and process messages with dynamic scaling based on the specified number of worker processes.

The MyApp.MessageConsumer module is configured with the following options:

• queue_name: Specifies the name of the queue from which messages will be consumed. In this example, the queue name is set to "queue_name".

• routing_key: Defines the routing key used to filter messages. In this example, the routing key is set to "routing_key".

• exchange: Defines the exchange from which messages will be consumed. In this example, the exchange is set to "exchange".

• consumer_count: Indicates the number of worker processes that should be used to handle incoming messages. In this example, consumer_count is set to 10, which means that 10 worker processes will be run to consume and process messages concurrently.

• auto_scaling: Allows configuration for dynamic scaling of consumers:

• min_consumers: The minimum number of consumers to maintain.

• max_consumers: The maximum number of consumers to maintain.

• messages_per_consumer: The number of messages each consumer should handle before scaling adjustments are considered.

• check_interval: The interval (in milliseconds) at which to check the queue length and adjust the number of consumers accordingly.

defmodule MyApp.MessageConsumer do
use HareMq.DynamicConsumer,
  queue_name: "queue_name",
  routing_key: "routing_key",
  exchange: "exchange",
  consumer_count: 10

# Function to process a received message.
def consume(message) do
  # Log the beginning of the message processing.
  IO.puts("Processing message: #{inspect(message)}")
end
end

MessageConsumer with auto scaling

defmodule MyApp.MessageConsumer do
use HareMq.DynamicConsumer,
  queue_name: "queue_name",
  routing_key: "routing_key",
  exchange: "exchange",
  consumer_count: 10,
  auto_scaling: [
    min_consumers: 1,
    max_consumers: 20,
    messages_per_consumer: 100,
    check_interval: 5_000
  ]

# Function to process a received message.
def consume(message) do
  # Log the beginning of the message processing.
  IO.puts("Processing message: #{inspect(message)}")
end
end

Usage in Application: MyApp.Application

defmodule MyApp.Application do
use Application

def start(_type, _args) do
  children = [
    # Start the message consumer.
    MyApp.MessageConsumer,

    # Start the message producer.
    MyApp.MessageProducer,
  ]

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

Configuration

config :hare_mq,
:amqp,
  host: "localhost",
  url: "amqp://guest:guest@myhost:12345",
  user: "guest",
  password: "guest"

config :hare_mq, :configuration,
delay_in_ms: 10_000,
retry_limit: 15,
message_ttl: 31_449_600

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