© 2019
© 2019
This variant uses the docker image from spring-green, but caches all the requests that that container makes to the API with Nginx. So the request from the end-user always goes to the spring-green container, but requests from the spring-green container to the API might get cached by Nginx.
Initially the Nginx cache will be configured to cache everything it can. In the future this configuration will require re-consideration, as the requirements of the Gatling script start including changes to the state of the data, making the cache invalid.
Building this variant was significantly more work than I expected. This was partially due to the fact that I (initially) wanted the spring-green image to remain unchanged, which required me to redirect its calls to the API from outside the image. After many new lessons in (docker) networking, HOSTALIASES, etc. I found no solution that could be implemented in reasonable time. In the end I changed the spring-green image so it would read the API url from an environment variable.
Configuring Nginx to cache JSON server had its own challenges: JSON server returns some headers indicating its output
should not be cached. Complementary to that I missed something in the "Can Cache-Control Headers Be Ignored?" section of
the Nginx caching guide, namely that ignoring the Cache-Control headers
requires setting a value for proxy_cache_valid. If you don't do that, Nginx will quietly not cache anything.
This was also the first project where I added a docker-compose development override config file. This allowed me to approach the cache container directly with my browser, which made figuring out all the above a LOT easier. Usage:
docker-compose -f docker-compose.yml -f docker-compose.development.yml up