Kubelet in Kubernetes | Deep Dive Guide Barely 10 Minutes

Kubelet Basic Definition one of the two main components on a worker node (the other is kube-proxy, a network proxy used to enable network comms). "node agent" or "bridge" ("supervisor/manager of a department" or "lieutenant" i.e. manages resources) Actually a Linux daemon (background process, similar to windows service). starts at boot and not usually interacted with. What Does Kubelet Do? One-Liner: it manages containers on it's node. Registers node with the apiserver (automatically by default) Receives podspecs (desired states) ensures those mentioned containers are running and healthy i.e. create, update or delete usually receives from apiserver but can be also from file or http endpoint by interacting with the node's container runtime (e.g. containerd). What Does Kubelet Do? Part II ** Constantly trying to ensure the desired state via control loop. ** Container health monitoring (to ensure health) Manages container lifecycles (starting, stopping, restarting) Ensures node cpu and memory resources are not exhausted Metrics Each K8s component has its own metrics, including kubelet. Prefixed "kubelet_" Exposed http endpoint on /metrics on port 10250 on the node Better to scrape it with monitoring solution like Prometheus Examples: sum(kubelet_node_name) sum(kube_node_status_condition{condition="Ready", status="true"}) kubelet_running_pods [check vs pod limit per node, usually 110] kubelet_runtime_operations_errors_total [consistent, low amount]