SchemaRegistry

Schema Registry is a collection of micro service message's specifications. This gem is a tool to create and maintain this spec collection.

Please find this good read about why you want to use schema registry: Using a schema registry to ensure data consistency between microservices.

This gem is designed to check your messages before serialization. It works with messages that are composed in a form of Hash.

Installation

You need to have this gem in your repository. It's designed to be modified, hosted at your versions control and required by your services.

So git clone it or fork it instead of installation.

Make sure your add your source to Gemfile:

$ gem 'schema_registry, git: your-repository

Usage

Set up

Schema Registry is a collection of your specifications, therefore first step is actually to create one.

Specifications are described in separate Modules that are used by the gem.

1. Create new module under lib/schemas folder
2. Write down spec

def character_created # this will be used as a name to look up your schema in the register
  # general structure is following
  # verify key, type or other check
  verify :name, String
  # there is an alias for verify - 'v', to make notation more concise
  v :age, Integer
  # if there is nested group, then one need to change analyzed subject as following
  @subject = v :data, Hash
  # then everything as usual 
  v :id, method(uuid?) # one can define predicate functions and put them as a verification method
  v :date, optional(DateTime) # optional allows field value to be nil
  v :home # or you can skip second argument for verify and it will check only key presence in the message
  # if one need to go back to top level, then reset subject back to the message
  @subject = @message
  @subject = v :additional_data, optional(Hash)
  # you can use normal logic here
  return if @subject.nil?
  v :favorite_food, 'Banana' # you can enforce data to be specific value
end

Refer demo items and rspec files.

Utilization

Validate message to be per spec before publishing it to the broker. Use either validate! to get an exception, or validate to get false on failure.

require 'schema_registry'

message = {
  name: 'Luke',
  age: 15,
  data: {
    id: SecureRandom.uuid,
    date: nil
    },
  additional_data: nil
}

if SchemaValidator.new(message, :character_created).validate 
  MessageBrokerClient.publish(message)
end

Notes

Schema naming: currently there is a common namespace for all schema modules, therefore it may result in a clash if names are the same. Thus it's recommended to use service name as a prefix, e.g. auth_account_created.

Validation checks that all fields in the spec are present in the message. Other fields that may be in the message, they will be ignored.

Available checks:

• specific values, e.g. 23, 'Banana' - validation passes only if message and spec values are the same
• types, e.g. String, Integer - is_a? method is used to verify that message values is of certain class
• optional - allows to accept nil value as valid one, but key still has to be present in the message
• uuid? - custom predicate to verify that string is an uuid

Customization

You can define your own checks as a predicates (functions that return true of false). Then use mehtod(your_function) to use it as a check value.

Contributing

Please use issues for bug reports and feature requests, and pull requests are always welcome!

License

The gem is available as open source under the terms of the MIT License.