class NATS::Services

• NATS::Services
• Reference
• Object

Overview

The NATS Services API allows you to build microservices using NATS instead of HTTP. Since NATS has the concept of request/reply messages through a decentralized message broker, you don't need to deal with domain names, load-balancing, service meshes, or other concepts that you might have to implement in HTTP-based microservices. NATS takes care of all of those for you.

inventory = nats.services.add "inventory",
  version: "0.1.0",
  description: "Manage store inventory"

# Add the top-level subject namespace for the service
inventory.add_group "inventory" do |inv|
  # Add a namespace specifically for managing products
  inv.add_group "products" do |products|
    # Create a product. Receives a CreateProductRequest and returns a Product.
    # Example using the NATS CLI:
    #   nats req inventory.products.create '{"name":"Computer","description":"It is a computer","price_cents":200000}'
    products.add_endpoint "create" do |request|
      # Deserialize the request body and make a product out of it
      product = CreateProductRequest.from_json(request.data_string).product
      # Save the product to our KV store
      products_kv[product.id.to_s] = product.to_json
      # Reply with the serialized product
      nats.reply request, product.to_json
    end

    # Return the product with the given id passed in the subject.
    # Example: inventory.products.get.0197e31f-3ffa-7fd7-8512-a331a20e5ae3
    # Equivalent to the following HTTP request:
    #   GET /inventory/products/0197e31f-3ffa-7fd7-8512-a331a20e5ae3
    products.add_endpoint "show", subject: "get.*" do |request|
      # Split the subject to get the id
      _, _, _, product_id = request.subject.split('.')

      # Fetch the product from the `inventory-products` KV bucket
      nats.reply request, products_kv[product_id]
    end
  end
end

Defined in:

Constant Summary

NAME_PATTERN = /\A[\w\-]+\z/

Instance Method Summary

• #add(name : String, *, version : String, description : String, metadata : Hash(String, String) = {} of String => String)

  Register a service with the NATS server.

Instance Method Detail

inventory = nats.services.add "inventory",
  version: "0.1.0",
  description: "Manage inventory"