The Harmony Service gem simplifies creation of a micro-service (Service) in the Harmony Platform.

You can connect your Service to pages and Apps inside Harmony. Whenever a page or App connected to your service is triggered it will route a message through to your service with a representative class. You should respond with the appropriate class encapsulating any data you want to display. For example, if your Service recieves a Harmony::Service::Chart::Request, it should return a Harmony::Service::Chart::Response.

You can find the relevant mappings here.


  1. Create a new Service via the Harmony platform
  2. Download the Harmony Service Template.
  3. Add your own code. You will need to use your own source code control.


In order to test your code locally you can run bundle exec rspec. Once you have completed development you can upload into Harmony Platform.

The service has 9 request models at the moment, namely..

Model Purpose
Action List Provide a list of purchase order items for approval or rejection
Calculator Turn a loan calculation spreadsheet into an optimised mobile app
Chart Display Data and various other chart types
Document Product briefs, presentations, and other documents for the app
Capture Capture documents or evidence
Instruction Text and Images to help use the app
Video Stream viedos and content
Webpage Embed a company webpage or URL
Form Create forms to document and photograph health and safety incidents

For the first integration use case, let's walk through the creation of a simple Harmony Calculator based service. For this we will be cloning the Harmony Service Weather example and integrate it with the Harmony environment. you can use the documentation present in that repository to understand how the service works.

Go to OpenWeatherMap.org and get a free API key, follow instructions on how to setup the service on the Harmony service plugin that incorporates this feature. From the documentation presented we examine the service

def work_with_request(request)
  case request
  when Harmony::Service::Calculator::Request
    if request.inputs && request.inputs.include?('city') && request.outputs.include?('temperature')
      city = request.inputs['city']
      weather = weather_service.current_temperature(city)
      Harmony::Service::Calculator::Response.new({outputs: {temperature: weather}})          
      Harmony::Service::Calculator::Response.new({outputs: {city: ['London','New York,US','Bangalore']}})

def weather_service
  @weather_service ||= WeatherService.new(ENV['open_weather_map_api_key'])

From the above service code we can notice that we request the service setup for two kinds of interaction, first being the standard use case of passing City as an input and expecting Temperature as an output. Most of the straight forward query integrations would do well with the Calculator request model

The interface gives us access to :uri, :inputs, :outputs that can be passed in as a Request, while the Response channel gives us :outputs. The service invokes the work_with_request function, which as you can see hooks up to the weather service by passing the city parameter to it. if there are no inputs the service will respond with the ideal inputs. Once the service has been prepared and automated tests have been installed, let's prepare the service for apps on Harmony.

  1. Log into www.harmonyplatform.io

  2. Click on Services, select +New

  3. Choose Custom, Create service

  4. Under New Custom Service, Choose a name - let's call it Weather Checker

  5. Leave the permission type as-is

  6. Create an environment variable open_weather_api_key to be used by the service and populate it with the one obtained from the website. this populates config/application.yml via Figaro o be


  1. In the repository folder, run the packaging command as indicated in the build box, to generate a compressed image in the builds folder. select Choose file and pick the said file.


  1. Click on Create build, which triggers an upload. wait for the status to say Build succeeded. this should take a few minutes.

  2. Click on Apps, on the main navigation bar, and selected +New, Enter a name

  3. Select Add a Page, and choose Calculator

  4. In Inputs type City and in Outputs type Temperature, this must correspond to what the service recieves as per the code above. select the service that we just setup, the names don't have to match.


  5. Choose Save & Test, You shold be able to get a result from the service here

  6. Now enter Harmony App and test out the same and see if the output matches

Once you get it working, this can serve as a template to modify and integrate your own services, and extend this to include multiple inputs, mutiple services and several pages to suit your business needs.


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