Full Stack Engineering Exercise

Hi Brightwheel engineers,

Here you will find my app answering a downtime problem during an email service provider outage.

Launch the app:

To see how it works you need to:

1. Install the environment:

   • JDK 1.8
   • Gradle 2.3+

2. Download the code.

3. Insert the keys:

   • Put the API key values file Keys.java

4. Build the code:

   • execute in a terminal gradle build (make sure Gradle is in your PATH)

5. Run the app:

   • java -jar build/libs/gs-rest-service-0.1.0.jar

6. Send an HTTP POST request with your Json to:

   • http://localhost:8080/email

All frameworks and libraries are downloaded thanks to the build.gradle file. The main framework I used to build the HTTP service is Spring Boot. Here is a list of all the frameworks included in this project:

• Java Platform, Standard Edition 8
• Spring Boot: for the main application running the HTTP service.
• Jackson: a powerful Json parser.
• Jsoup: a HTML parser for formatting the html body of the email.

A word on this exercise:

The application waits for a POST request at the `http://localhost:8080/email` endpoint, and sends the email through an email service provider selected in a list of different providers. If there is an error on the provider side, ie. if the returned HTTP status is of the form 5xx, the application choses another provider, and sends again... And so on until there's no remaining provider. In the exercise, there's only two of them: Mailgun and Sendgrid. However, I experienced troubles setting up an account at Sendgrid: while creating a Mailgun account has been easy and quick, for Sendgrid it has been another story. I then tried with other providers: at Sendinblue, Mailchimp, Sparkpost and Amazon SES, but either they didn't support transactional emails, or they didn't allow sending emails to a single recipient. Finally I found Elasticemail which allowed me to do it, and thus to send an email to the address in the Json provided in the POST request.

I choose email providers within a for loop so one can try to send the email with one provider at a time, this way we can add further providers later. However, each provider has a different API and sets of parameters for POST requests, so I defined a send method for each of these providers.

The tests are not finished yet, I experienced some issues when trying to create "simulated" email providers on a separate local endpoint. To correctly test the Mailgun and Elasticemail send functions, I tried to create dedicated 'fakeservice' enpoints to send back specific status and exceptions using the actuator package provided by Spring boot. However the import didn't work. Then I tried to create a second FakeService class using the @Controller annotation mapped to a 'fakeservice', in addition to the EmailController class used for the 'email' endpoint. But to do so, the Springboot application must be running at the same time, and the fake endpoint could not be reached since the associated FakeService wasn't in running in parallel. What I'm going to try is then to create a second Java project to create fake services at specific endpoints, and launch their executions when running the tests for the main HTTP service.