To decrease the load on the Kubernetes API server, by default the Controller polls for any changes every 5 minutes. This project can be found in GitHub.Ī downside of this solution is that the updates to the Pods are still happening out-of-bounds from the overall deployment. It keeps a list of which Deployments use what ConfigMaps, and ensure that pods are recreated when a used ConfigMap is changed. One such solution was recently shared by The New Stack, who have created a Controller that continually tracks changes to ConfigMaps. Of course the Kubernetes community is creative enough to come up with solutions to solve this drawback. Almost 2.5 years later there is still no built-in solution in Kubernetes. Interestingly enough, a GitHub issue has been open regarding this issue since 2016. Also, it goes against the notion of immutable containers. The configuration that is updated “at some point” may break the application but as this is an out-of-bound process from the deployment, rollbacks are harder to implement. This introduces unreliable deployments though. When a ConfigMap is updated, the files in the volume are “ eventually updated as well". The only exception here is when mounting configuration to volumes. It is only through re-creating the containers that configuration updates would become available. What this means is that when configuration is updated, the Pod or Deployment that uses it is not triggered and the container will not pick up the latest changes. However, the lifecycle of these ConfigMaps is completely separated from the containers that uses it. These ConfigMaps can be referenced from Pods or Deployments and the values can be injected to the container using environment variables or files through volumes. The construct in Kubernetes to store such configuration is the ConfigMap. One such area is the lifecycle management of application configuration. Adoption is rising while at the same time, new users find out the areas where Kubernetes is still lacking. In recent years Kubernetes has quickly gained a lot of popularity and it currently has huge momentum.
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