#SETUP

• Spring boot application
• Wiremock server, mocking third party APIs
• Redis instance
  

To Launch the application, navigate to the root folder and run

docker-compose up

It will launch a Redis instance, on port 6380, and a wiremock server on port 8889

Run spring boot

mvn package

mvn spring-boot:run

Spring boot will run on port 8081

#Caching demo

• Open postman
• Call localhost:8081/person-details?id=1, with method GET. it will take at least 500 ms
• Call the API again immediately after, the call will take significantly less time, < 10 ms depending on system specifications
• Wait 30 seconds, and call the API again, it will take > 500 ms. This is because the entry got evicted

Explanation

• The service layer for /person-details calls a third party API, localhost:8889/details to get the required information
• localhost:8889/details is configured in Wiremock to respond with a delay of 500 ms. Refer to /resources/wiremock/mappings/person-details-success.json
• ApiGatewayServiceImpl has the functions that call third party APIs. During the first call, the response is cached in Redis, using RedisService, with a TTL of 30 seconds
• During the second call, the function finds the entry in Redis, and returns it immediately.
• After 30 seconds pass, Redis will evict the entry, and the service layer has to call the external API again

You can also observe the above using a Redis GUI, such as RedisInsights.