ServiceProtocol

Basic protocol for communicating between services.

Currently implements HTTP/JSON, see ServiceProtocol::Redis for an alternate adapter.

Features

• Designed to work with ServiceOperation but can interface with any class that respond to .call(params) and return an object that responds to #to_hash.
• Syncronizes metadata (user_id, trace_id, etc) between services via RequestStore.
• Uses #to_json to serialize complex objects in JSON:API format (See Serializtion note below).
• Allows batched requests.

Example

Call Math::MultiplyByTwo.call(input: 1) on the 'math service'

ServiceProtocol::Remote.call(
  'math_service:math/multiply_by_two',
  { input: 1 },  # params
  { user_id: 1 } # meta
)

=> { input: 1, output: 2 }

Environment Variables

SERVICE_PROTOCOL - Which adapter to use:

• "basic" - in process calls with serialization.
• "lib" - direct calls without serialization.
• "web" - HTTP/JSON.

SERVICE_PROTOCOL_TOKEN - A token to share across services to add basic security if service is exposed to public networks. Can be rolled by comma separating tokens (eg "old_token,new_token").

Serialization

Currently #to_json expects a hash in JSON:API format:

{ "id" : 1, "type": "ModelName", "attributes": { ... } }

To implement this in ActiveRecord::Base requires modifying the serialization method:

  alias serializable_hash_attributes serializable_hash

  def serializable_hash(options = {})
    attrs = serializable_hash_attributes(options)
    { 'id' => attrs.delete('id'), 'type' => self.class.name.demodulize, 'attributes' => attrs }
  end

Todo

• Decouple serialization strategy
• Move environment variables, logger and Proxy::REQUIRED_META_KEYS to Configuration.
• Better unit tests.
• Remove Hash#traverse dependency.
• BaseServer for authenticates? method
• Rename Proxy and Entity