My previous article “Inotify in Containers” has demonstrated that when ConfigMap is mounted as directories, any changes in the ConfigMap will propagate to related pods.
A follow-up question might be: what if the ConfigMap is mounted as environment variables?
Some said that the answer is NO in Kubernetes1; even in the old Docker world2. Therefore, I’d like to begin with a simple experiment to try to answer the question: After a container starts, will it see any changes of environment variables?
The experiment material is available at https://github.com/William-Yeh/container-and-env , and here’s a simple demo:
It is obvious in the demo that the changes of environment variables will not affect already-running processes inside the containers — let alone pods in the Kubernetes world.
To simply put, if you want ConfigMap to propagate its changes to related pods, mount the ConfigMap as directories, not environment variables.
❷ Containers and Environment Variables
- An analysis of ConfigMap hot-reload can be found in the article by Jimmy Song: “ConfigMap 的热更新”. [return]
- A good Q&A in Stack Overflow: Reload configuration when env variable has changed. [return]