Azure Cloud Service microservice to K8 Migration

2/2/2021

I am in the process of evaluating moving a very large Azure Cloud Service (Web Role) microservice architecture to AKS and have been working through the necessary code and build changes to support it.

In order to replicate the production environment locally for the developers, we run nginx on the host with SSL offloading and DNS (hosted in Azure) A records pointing to 127.0.0.1. When running in the Azure Emulator, the net affect is the ability for both the developer to visit the various web front ends in their browser (i.e. https://myapp.mydomain.dev) as well as hit the various API's in the solution (Web API 2) in Postman/cURL, etc.

Additionally due to how the networking of the Azure Emulator works, the apps themselves can resolve each other through nginx on the host (i.e. MVC app at https://myapp.mydomain.dev can obtain a token from the IdP web API at https://identity.mydomain.dev and then use that token at the API at https://api.mydomain.dev). This is the critical piece and the source of my question.

All attempts at getting the containers themselves to resolve each other the same way the host OS can (browser/Postman, SSL offloading via nginx) have failed. Many of the instructions out there are understandably for linux containers but having adapted the various networking docker-compose settings for the windows container equivalent have not yet yielded an success. In order to keep the development environments aligned with the real work systems, which are tenantized and make sure of the default mapping in nginx to catch all incoming traffic and route it to a specific user facing app/container, it is not as simple as determining a "static" method of addressing these on startup and why the effort was put in to produce the development environments we have today.

Right now when one service (container) attempts to communication with another, it ultimately results in a resolution error as all requests resolve to https://127.0.0.1 due to the DNS A records hosted in Azure for the domain. Since this migration will be a longer term project, the environments need to co-exist so changing the way that DNS is resolved (real DNS A records pointing to 127.0.0.1), host running nginx and handling SSL offloading to the various webroles normally running in the Azure Emulator is not an option.

Is there a way (with Windows containers) to either:

  • Allow the container to utilize nginx on the host OS transparently (app must still call the API at https://api.mydomain.dev), which will cause the traffic to be routed properly to the correct container/port defined in the docker-compose file?

OR

  • Run nginx on each container, allowing each container to then resolve and route appropriately without knowing the IP of the other container, possibly through an alias which could be added to the containers nginx.conf before the service starts?

The platform utilizes OAuth2/OIDC and it is critical to maintain the full URL to the other services from the applications perspective. Beyond mirroring production and sandbox environments, this URL's are utilized for redirect URL and post logout redirect URL validation among other things so using "https://myContainerNameForOtherContainerAlias" is not a workable solution.

Will I have the same problem when setting up the AKS environment as well?

-- James Legan
azure-aks
docker
kubernetes
nginx

0 Answers