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Liveness and Readiness in Kubernetes: 5 Essential Tips for Reliable Deployments

Posted on by Monika
liveness and readiness probes in kubernetes

Introduction

Liveness and readiness in kubernetes are key features in Kubernetes that ensure your application is healthy and available. While  checks help restart unhealthy containers, readiness checks ensure only ready pods receive traffic.

 What Are Probes in Kubernetes?

In Kubernetes, both a probe is a diagnostic mechanism to check the status of a container running inside a Pod.

Kubernetes offers three types of probes:

  1. Live probe – Is the container alive?

  2. Readiness probe – Is the container ready to accept traffic?

  3. Startup probe – Has the container started correctly? (introduced in Kubernetes v1.16)

 What is a Liveness Probe?

It probe checks whether a container is still running. If this check fails continuously, Kubernetes will restart the container automatically.

Why is it important?

Sometimes, a container might appear to be running (from the OS point of view), but the application inside is deadlocked, stuck, or in an unrecoverable state. It probes catch such situations.

Behavior:

  • If the live probe fails, Kubernetes kills and restarts the container.

  • The container restart follows the pod’s restart Policy (usually Always in Deployments).

liveness and readiness probes in kubernetes

 What is a Readiness Probe?

A readiness probe checks whether the container is ready to serve traffic. If the check fails, Kubernetes will temporarily remove the Pod from the Service endpoints, i.e., it won’t receive traffic.

Why is it important?

Your application may need time to:

  • Load data from disk or database

  • Warm-up caches

  • Connect to third-party services

If you route traffic too early, it may result in errors. Readiness probes delay traffic routing until your app is truly ready.

 Behavior:

  • If the readiness probe fails, the Pod is marked as not ready

  • The container is not restarted

  • The Pod remains running, but doesn’t receive traffic from Services

liveness and readiness probes in kubernetesDifferences between liveness and readiness in kubernetes

Feature Liveness Probe Readiness Probe
Purpose Checks if the container is alive Checks if the container is ready to serve traffic
Failure Action Restarts the container Removes the Pod from Service endpoints
Triggered By Deadlocks, stuck threads Initialization, temporary failures
Recovery Requires restart Automatically re-added when ready
Service Exposure Does not affect service routing Affects service load balancing

Types of Probes in Liveness and readiness in kubernetes

All probes (liveness, readiness, startup) support the following types:

1. HTTP Probes

Make an HTTP GET request to a specified endpoint in the container.

httpGet:
path: /healthz
port: 8080

2. TCP Socket Probes

Attempt to open a TCP connection to the container.

tcpSocket:
port: 3306

3. Exec Probes

Run a command inside the container. Exit code 0 is success.

exec:
command:
- cat
- /tmp/healthy

  Example

live Probe:
httpGet:
path: /healthz
port: 8080
initialDelaySeconds: 10
periodSeconds: 5
timeoutSeconds: 2
failureThreshold: 3

 Explanation:

  • Kubernetes starts checking after 10 seconds

  • Every 5 seconds, it hits /healthz

  • Timeout is 2 seconds

  • After 3 failures, the container is restarted

Readiness Probe Example

readinessProbe:
httpGet:
path: /ready
port: 8080
initialDelaySeconds: 5
periodSeconds: 10
timeoutSeconds: 2
failureThreshold: 1

Explanation:

  • Starts after 5 seconds

  • If /ready fails even once, Pod is marked unready

  • It won’t receive any traffic from the service

 Real-World Use Cases

 Microservices

In microservice architectures, readiness probes prevent routing traffic to a Pod that hasn’t connected to its database or messaging service yet.

 Database Initialization

Some apps need to perform database migrations at startup. Readiness probes ensure they don’t serve traffic until that’s done.

 Long-lived APIs

API servers might hang or deadlock. Live probes detect these and trigger restarts.

 Conclusion

Liveness and readiness in kubernetes  probes are essential for running resilient and self-healing Kubernetes applications. They offer a way to detect when containers are:

  • Alive and healthy

  • Ready to handle traffic (readiness)

By configuring these probes properly, you reduce downtime, prevent broken apps from receiving traffic, and ensure smoother rollouts and scaling operations.

Kubernetes, don’t miss our guide on Kubernetes the Hard Way.

For official documentation, check out the Kubernetes Probe Docs.

Want to understand Kubernetes architecture better? Read our detailed  Beginner’s Guide to Kubernetes. click here