kube-controller-manager Controllers: A Glossary

The ????????-????????????????????-?????????????? is a crucial component of the Kubernetes control plane, responsible for managing various controllers that ensure the desired state of the cluster is maintained. Below is a list of both the default controllers managed by the ????????-????????????????????-?????????????? and additional controllers that may be present.

D?e?f?a?u?l?t? ?C?o?n?t?r?o?l?l?e?r?s? ?M?a?n?a?g?e?d? ?b?y? ?k?u?b?e?-?c?o?n?t?r?o?l?l?e?r?-?m?a?n?a?g?e?r?:

? ?????????????????????? ?????????????? ????????????????????: Manages the signing of Kubernetes certificates to ensure secure communication between various components in the cluster.

? ?????????????? ????????????????????: Manages the execution of time-based jobs (CronJobs), ensuring they run at specified times and handle failures and retries.

? ?????????????????? ????????????????????: Ensures that a specific pod runs on all or selected nodes in the cluster, which is useful for cluster-wide services like logging and monitoring.

? ???????????????????? ????????????????????: Manages Deployments, ensuring the desired number of Pods are running and updated.

? ?????????????????? ????????????????????: Populates the Endpoints object to link services with their corresponding pods, enabling the routing of traffic to the correct locations.

? ???????????????????? ?????? ???????????????????? ????????????????????: Automatically adjusts the number of pods in a replication controller, deployment, or replica set based on observed CPU usage or other application-specific metrics.

? ?????? ????????????????????: Manages Job resources to ensure that a specified number of pods successfully terminate, handling batch processing and parallel jobs.

? ?????????????????? ????????????????????: Manages the lifecycle of namespaces, ensuring resources within namespaces are created and deleted as needed.

? ???????? ????????????????????: Monitors the status of nodes in the cluster, detecting node failures, and taking appropriate actions like evicting pods running on unhealthy nodes.

? ???????????????????? ???????????? ????????????????????: Manages the lifecycle of PersistentVolume and PersistentVolumeClaim objects, ensuring that storage volumes are available and bound correctly.

? ?????????????????????? ????????????????????: Ensures that a specified number of pod replicas are running at any given time; considered legacy and largely replaced by ReplicaSet Controller.

? ???????????????????? ????????????????????: Ensures that a specified number of replicas of a pod are running, which is crucial for maintaining application availability.

? ?????????????????????????? ????????????????????: Enforces resource usage limits in namespaces by monitoring and managing the usage of resources like CPU, memory, and storage.

? ?????????????? ???????????????? ????????????????????: Automatically creates and manages default ServiceAccounts for newly created namespaces, enabling secure access to the Kubernetes API.

? ?????????????? ????????????????????: Manages the lifecycle of Service resources to ensure the correct mapping of services to pods, facilitating stable network connections.

? ?????????????????????? ????????????????????: Manages StatefulSets to ensure the deployment and scaling of stateful applications, maintaining stable network identities and storage.

A?d?d?i?t?i?o?n?a?l? ?C?o?n?t?r?o?l?l?e?r?s?:

? ?????????????????????? ?????????????????????? ????????????????????: Manages the aggregation of multiple ClusterRoles to create composite roles that simplify access control.

? ???????????????????? ????????????????????: Manages PodDisruptionBudgets to control the voluntary disruptions (like maintenance) of pods, ensuring application availability.

? ???????????????? ?????????? ????????????????????: Manages EndpointSlices for more scalable endpoint representation, improving the performance and scalability of network traffic routing.

? ?????????????? ?????????????????? ????????????????????: Cleans up orphaned resources that are no longer in use, maintaining cluster hygiene and freeing up resources.

? ?????? ????????????????????: Manages TTL-based cleanup for finished resources like Pods and Jobs, automatically deleting them after a specified period.

These controllers work in concert to maintain the health and desired state of the Kubernetes cluster by continuously monitoring resources and making necessary adjustments based on defined specifications.

Note that the specific set of controllers managed by the kube-controller-manager may vary depending on the Kubernetes version and distribution you are using. This list isn't exhaustive, as the Kubernetes ecosystem is constantly evolving, with new controllers being added or modified.

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