Architecture (Outdated)

Current architecture design as discussed starting 16/04/2020

This is the current view of how the service will work, with the back end making calls out to TIS Core to pull in data not duplicated in Revalidation.

The disadvantage with this approach is the tight coupling between the back end and TIS Core which means routing complexity, monitoring and recovery is added to the back end. Managing messages to other services should not be the responsibility of the back end.

The complexity of the back end will be increased each time it needs to talk to another service, e.g. Self Service for Form Rs or future GMC Connect APIs.

Long term design featuring a message broker

In the long term, integration could be performed using an off the shelf product, such as AWS MQ and Apache Camel.

AWS MQ integrates with Apache Camel and can be used to provide a sophisticated message broker service which supports multiple messaging patterns out of the box. Implementing this solution will de-couple micro-services from each other, allowing greater flexibility when it comes to changing existing services or adding extra services that need to be consumed.

With our current, envisaged configuration there would be very little custom code required to be written for the integration service. Most of our requirements would be handled by configurable settings in Camel.

Single request/response timeline

This diagram shows the path a request takes through the components of the service in the case of a request for dynamic data from the back end. The diagram illustrates the use of a controller, but the concept is the same where no controller or a broker is used.

The steps are

1. The client makes a request from the internet

2. Route 53, or other DNS directs the request to the Revalidation service

3. The WAF checks the incoming request is acceptable

4. API Gateway routes the message to the controller

5. The controller routes messages to the back end and TIS Core via private API Gateway calls

6. The back end and TIS Core send their responses back to the controller via the gateway

7. The controller aggregates the response and returns it to the public API Gateway

8. The public API Gateway sends the response back to the client via the WAF and Route 53.

Current Implementation

This is the current implementation in stage-revalidation as at Fri 24/04/2020:

Detailed AWS Architecture

This is the architecture for the Revalidation service as at Friday, 18/05/2020

Updated Architecture - JS - 19/05/2020

Needs to be made pretty using draw.io - files above

An attempt by Phil using the famous artist Babul for inspiration

Draw.io files

SVG File