What factors contribute to the completion speed of…

The termination of pods in Kubernetes is regulated by the following factors:

terminationGracePeriodSeconds: Defines the time given to applications in a pod for proper termination (handling current requests, closing connections, etc.) after receiving the SIGTERM signal. If the application does not terminate within this time, a SIGKILL is sent.

apiVersion: v1
kind: Pod
metadata:
  name: my-pod
spec:
  containers:
  - name: app
    image: my-image
  terminationGracePeriodSeconds: 30 # Default value - 30 seconds

** preStop Hook:** Allows executing specific actions before sending SIGTERM. For example, stopping acceptance of new connections.

apiVersion: v1
kind: Pod
metadata:
  name: my-pod
spec:
  containers:
  - name: app
    image: my-image
    lifecycle:
      preStop:
        exec:
          command: ["/bin/sh", "-c", "nginx -s quit"] # Example: proper shutdown of Nginx

** readiness and liveness probes:** Determine the readiness and "alive" state of the pod. If pods become "not alive" (livenessProbe fails) or "not ready" (readinessProbe fails, and the controller sees that the pod is no longer needed), they can be terminated.

apiVersion: v1
kind: Pod
metadata:
  name: my-pod
spec:
  containers:
  - name: app
    image: my-image
    readinessProbe:
      httpGet:
        path: /ready
        port: 8080
      initialDelaySeconds: 5
      periodSeconds: 3
    livenessProbe:
      httpGet:
        path: /live
        port: 8080
      initialDelaySeconds: 15
      periodSeconds: 5

** Desired State:** Kubernetes controllers (e.g., Deployment, ReplicaSet) aim to maintain the specified number of replicas. When the Desired State changes (decreasing the number of replicas) or during updates, pods that are no longer needed start to terminate. The speed of this process depends on the update strategy (e.g., RollingUpdate) and parameters like maxUnavailable.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-deployment
spec:
  replicas: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxUnavailable: 1 # Defines how many pods can be unavailable during update
      maxSurge: 1

** Node Drain:** When a node is put into maintenance mode (kubectl drain), Kubernetes terminates the pods on that node. The speed also depends on terminationGracePeriodSeconds and the —ignore-daemonsets setting.
** Application responding to SIGTERM:** The application inside the pod should handle the SIGTERM signal properly and be able to finish its work within the terminationGracePeriodSeconds.

Factor	Impact on termination
`terminationGracePeriodSeconds`	Time for proper termination after `SIGTERM`
`preStop Hook`	Actions before `SIGTERM`
Readiness/Liveness Probes	Triggers for initiating termination process
Desired State / Strategy	Number and speed of termination during replica change/update
Node Drain	Termination of all pods on a node for maintenance
Handling `SIGTERM` in application	Application's ability to terminate itself properly

What factors contribute to the completion speed of pods according to set time management?