Which tag is included at high cardinality for container metrics on Kubernetes?

The correct answer is container_id because it is a tag that exhibits high cardinality in the context of container metrics on Kubernetes. High cardinality refers to having a large number of unique values within a dataset. In Kubernetes, each container is assigned a unique identifier known as the container ID. Since containers can be created and destroyed frequently, the number of unique container IDs can be very high at any given time, making this tag especially valuable for monitoring and analyzing performance and resource usage on an individual container level.

Tags like pod_name, service_name, and namespace are generally more limited in their uniqueness. For example, while pod_name will vary between different deployments and may have a significant number of unique values, it usually does not reach the high levels of unique identifiers represented by container IDs. Similarly, service_name and namespace are used for organizational purposes but typically do not exhibit the same level of uniqueness as container_id, hence they do not demonstrate high cardinality to the same extent. Understanding this distinction is crucial for effective monitoring and performance tracking in Kubernetes environments.