the event listener

What are we building

The (SendGrid) Event Activity service is a REST microservice that

• accepts information from SendGrid's webhook service (SendGrid Webhooks)

• publishes that information to a Kafka queue

• performs minimal formatting of data or the payload

Background

When we submit a request to SendGrid we get an immediate response that the request was received. We can also get asynchronous event activity messages from Sendgrid about the delivery progress and how the recipient interacted with the email.

In order to get these we need to set up a REST 'endpoint' that listens for the messages, and we need to tell Sendgrid to send the messages to our endpoint.

The basic flow

• SendGrid completes processing of the request

• The email makes it to the recipient (or not)

• The recipient opens the email (or not)

• The recipient clicks on any link that we've embedded in the email (or not)

The event activity service

The Event Activity service will listen for these messages and store the raw data in Kafka for further processing. Unlike the Sendgrid mailer service, we replace the controller with a reactive router so that we can explore testing that sort of service. In the next few sections we'll

• Do a brief walk-through of the code

• Explore testng the reactive router

• Explore testing a message service client