# Exercise 5: Health checks

In Kubernetes, liveness and readiness probes are essential for smoothly running applications. A probe is generally a REST `GET` call, but there are other types of probes available. Liveness probes are used to determine when to restart a container. For example, an application that is unhealthy and no longer responding to an API call would be restarted by OpenShift. Readiness probes determine when a container is ready to start receiving traffic. If a readiness probe fails, then the load balancer would deregister that service.

## Create Readiness and Liveness Probes

The `/info` endpoint on the Example Health application is a great way to check whether the application is running and responding to API calls -- it responds with a simple JSON payload.

Go ahead and click on the deployment view. You should see something like `node-s-2-i-openshift`. Click `Actions > Edit Deployment`. Find the `containers` line probably line *38*. Under the `resources` line, so line **46** past the following `yaml`. This will add a liveness probe to your deployment!

```yaml
    livenessProbe:
      initialDelaySeconds: 5
      periodSeconds: 2
      httpGet:
        path: /info
        port: 8080
```

Now, next step is to add a readiness probe. Luckly it's on the same page, imediatly under the `livenessProbe` stanza you entered, paste the following:

```yaml
    readinessProbe:
    initialDelaySeconds: 5
    timeoutSeconds: 2
    httpGet:
      path: /info
      port: 8080
```

This will make sure when a new deployment happens that it won't start until the `/info` path is available.

If you want to verify it, you can run the following command to check the status, you should see something like this in the output:

```bash
oc describe deployment node-s-2-i-openshift
```

```
Liveness:     http-get http://:8080/info delay=5s timeout=1s period=2s #success=1 #failure=3
Readiness:    http-get http://:8080/info delay=5s timeout=2s period=10s #success=1 #failure=3
```

If all works, everything should be the same. Let's check that the probes are really working though.

## Inject Failure

Let's edit the probe with a typo to see what happens when it fails. Edit the health check and change the path for the readiness probe to `/badpath`. Wait a few minutes and check your deployment - you'll notice that `0/1` containers are ready:

![Badpath](https://1137660015-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-Lo1CthFUNGt5R3JtwjG%2F-LpZs2v9MhvPXFGOm_bZ%2F-Lo6FR0BVQUQxq0m9usu%2Fbadpath.png?generation=1569355628354504\&alt=media)

Dive into your events and you'll see that the probe is failing, causing the platform to try and repeatedly restart your pod.

![Deeper Dive](https://1137660015-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-Lo1CthFUNGt5R3JtwjG%2F-LpZs2v9MhvPXFGOm_bZ%2F-Lo6FR0DC4GvPoNkh40D%2Fevents.png?generation=1569355554033585\&alt=media)

Using health checks gives your OpenShift service layer better reliability and helps you start with a strong foundation.