Probe timing parameters (initialDelay, period, timeout) in Kubernetes - Commands & Configuration

Introduction

Kubernetes uses probes to check if your app is healthy and ready. Probe timing parameters control when and how often these checks happen, helping avoid false alarms and ensuring smooth app operation.

When your app needs some time to start before Kubernetes checks if it's ready

When you want Kubernetes to check your app's health regularly to restart it if it fails

When your app sometimes takes longer to respond and you want to avoid marking it unhealthy too soon

When you want to control how long Kubernetes waits for a probe response before considering it failed

Config File - pod.yaml

pod.yaml

apiVersion: v1
kind: Pod
metadata:
  name: example-pod
spec:
  containers:
  - name: example-container
    image: nginx:1.23
    livenessProbe:
      httpGet:
        path: /healthz
        port: 80
      initialDelaySeconds: 10
      periodSeconds: 5
      timeoutSeconds: 2
    readinessProbe:
      httpGet:
        path: /ready
        port: 80
      initialDelaySeconds: 5
      periodSeconds: 3
      timeoutSeconds: 1

This pod configuration defines two probes: livenessProbe and readinessProbe.

• initialDelaySeconds sets how many seconds Kubernetes waits before starting the first probe after the container starts.
• periodSeconds sets how often Kubernetes runs the probe.
• timeoutSeconds sets how long Kubernetes waits for the probe to respond before marking it failed.

These settings help Kubernetes know when your app is ready and healthy.

Commands

This command creates the pod with the defined probes and their timing parameters.

Terminal

kubectl apply -f pod.yaml

Expected Output

pod/example-pod created

This command checks the status of the pod to see if it is running and ready.

Terminal

kubectl get pods example-pod

Expected Output

NAME          READY   STATUS    RESTARTS   AGE

example-pod   1/1     Running   0          10s

This command shows detailed information about the pod, including probe events and timing details.

Terminal

kubectl describe pod example-pod

Expected Output

Name:         example-pod

Namespace:    default

Containers:

  example-container:

    Container ID:   docker://abcdef123456

    Image:          nginx:1.23

    State:          Running

    Ready:          True

    Restart Count:  0

    Liveness:       http-get http://:80/healthz delay=10s timeout=2s period=5s

    Readiness:      http-get http://:80/ready delay=5s timeout=1s period=3s

Events:

  Type    Reason     Age   From               Message

  ----    ------     ----  ----               -------

  Normal  Scheduled  1m    default-scheduler  Successfully assigned default/example-pod to node-1

  Normal  Pulled     1m    kubelet            Container image "nginx:1.23" already present on machine

  Normal  Created    1m    kubelet            Created container example-container

  Normal  Started    1m    kubelet            Started container example-container

Key Concept

If you remember nothing else from this pattern, remember: initialDelaySeconds waits before first check, periodSeconds sets check frequency, and timeoutSeconds sets how long to wait for a response.

Common Mistakes

Setting initialDelaySeconds too low so probes start before the app is ready

Kubernetes may mark the app as unhealthy and restart it unnecessarily.

Set initialDelaySeconds to a value that matches your app's startup time.

Setting timeoutSeconds too low causing probes to fail if the app responds slowly

Probes fail even if the app is healthy but slow, causing restarts.

Set timeoutSeconds to a reasonable value that allows your app to respond.

Setting periodSeconds too high, so failures are detected too late

Kubernetes takes longer to detect and fix unhealthy apps.

Set periodSeconds to a balanced value for timely health checks without overload.

Summary

Define probe timing parameters in pod.yaml to control health and readiness checks.

Use kubectl apply to create the pod and kubectl get/describe to verify probe behavior.

Adjust initialDelaySeconds, periodSeconds, and timeoutSeconds to match your app's needs.