Smarter Health Checks in Kubernetes: Mastering Liveness and Readiness Probes
In the fast-paced world of cloud-native applications, reliability and availability are no longer optional — they are expected.
When you are deploying containerized workloads using Kubernetes, it is critical to ensure that your applications are not only running but also healthy and ready to serve traffic.
That is where Liveness and Readiness Probes come into play.
These two built-in features are the secret sauce behind self-healing containers and smooth rolling updates in Kubernetes.
In this blog, we will take a deep dive into what they are, how they work, and why they’re essential for every modern Kubernetes deployment.
What Are Health Probes in Kubernetes?
Kubernetes provides health checks for your containers in the form of:
Liveness Probes
Readiness Probes
These probes are essentially periodic checks performed by the Kubelet to monitor the state of your application.
Liveness Probe: Is Your App Alive?
A Liveness Probe answers the question: “Is my application still running, or is it stuck in an unrecoverable state?”
If the liveness probe fails repeatedly, Kubernetes assumes your application is dead and automatically restarts the container.
Why it matters:
Prevents zombie containers that are running but non-functional.
Automatically recovers from runtime issues like deadlocks.
Reduces manual intervention for common failure scenarios.
Readiness Probe: Is Your App Ready?
A Readiness Probe checks: “Is my application ready to receive traffic?”
If the readiness probe fails, Kubernetes removes the pod from the Service’s endpoints, which means it won’t receive any incoming requests.
This is incredibly useful when:
The application needs time to warm up.
Background jobs are running before the app can serve traffic.
Temporary issues (like a failed database connection) need to be resolved first.
Real-World Benefits
Using liveness and readiness probes can significantly improve:
Availability – Only healthy pods get traffic.
Resilience – Kubernetes restarts unhealthy containers automatically.
Deployment Strategy – Smooth rollouts and rollbacks.
Load Balancing – Avoid traffic to unready or broken pods.
Autoscaling Efficiency – Horizontal Pod Autoscaler scales on live, ready pods.
Best Practices
Here are some guidelines to help you implement probes effectively:
Don’t probe too frequently — avoid unnecessary load.
Use different endpoints for liveness and readiness.
Gracefully handle shutdowns using preStop hooks.
Consider using Startup Probes if your app takes time to boot.
Conclusion
Kubernetes Probes may seem like a small configuration detail, but they have a huge impact on application stability and performance.
Start using Liveness and Readiness Probes if you care about uptime, user experience, and operational excellence.
They are not just optional. They are essential.
Types of Probes in Kubernetes
Kubernetes provides three different types of health checks, known as probes. Each type checks the application’s status in a unique way, allowing Kubernetes to monitor containers effectively.
1. HTTP GET Probe
This type of probe sends an HTTP GET request to a specific path inside the container.
If the application returns a successful response (like a 200 OK status), Kubernetes considers it healthy.
Use this when:
Your app exposes a web endpoint like /health or /ready to indicate it's running fine.
2. TCP Socket Probe
Instead of using HTTP, this probe tries to open a TCP connection on a specified port.
If it can connect, the container is marked healthy.
Use this when:
Your app doesn’t use HTTP (e.g., it's a database, a game server, or a custom TCP service).
3. Exec Probe
This probe runs a specific command inside the container.
If the command returns a success code (exit status 0), the container is healthy.
Use this when:
You want to perform a custom check — like verifying a file exists or a service is running inside.
Pick the probe type based on how your application behaves:
Use HTTP for APIs and web apps.
Use TCP for services that listen on ports but don’t expose HTTP.
Use Exec for internal or advanced checks (like checking logs, processes, or file system).