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https://github.com/mkilchhofer/healthcheck-demo
Simple app to learn about kubernetes health checks
https://github.com/mkilchhofer/healthcheck-demo
Last synced: 10 days ago
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Simple app to learn about kubernetes health checks
- Host: GitHub
- URL: https://github.com/mkilchhofer/healthcheck-demo
- Owner: mkilchhofer
- Created: 2019-10-23T08:23:09.000Z (about 5 years ago)
- Default Branch: master
- Last Pushed: 2020-08-31T21:19:11.000Z (about 4 years ago)
- Last Synced: 2024-10-12T23:37:42.285Z (25 days ago)
- Language: Ruby
- Homepage:
- Size: 17.6 KB
- Stars: 0
- Watchers: 1
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# Demo App to play with Kubernetes health checks
⚠️ This project is not actively maintained. As an alternative, use: https://github.com/kubernetes-up-and-running/kuard
The ruby sinatra app exposes two health endpoints:
* `/health/ready`
* `/health/live`
By default these endpoints return `200 OK` with a sample JSON body.
To simulate that the app in unhealthy, we can delete the files in `/tmp`:
* `/tmp/ready` affects API endpoint `/health/ready`
* `/tmp/live` affects API endpoint `/health/live`
## Additional endpoints
* `/` returns a simple `Hello world\n` (for curl and webbrowsers)
* `/env` returns all environment variables as JSON
## Usage
### Start the image with plain docker
```bash
$ docker run -d --rm -p 9292:9292 docker.io/kicm/healthcheck-demo
```
Open your browser and play with the different endpoints:
* http://localhost:9292/
* http://localhost:9292/env
* http://localhost:9292/health/live
* http://localhost:9292/health/ready
### Example deployment in Kubernetes
```yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: healthcheck-demo
spec:
replicas: 3
selector:
matchLabels:
app: healthcheck-demo
template:
metadata:
labels:
app: healthcheck-demo
spec:
containers:
- name: app
image: docker.io/kicm/healthcheck-demo
ports:
- containerPort: 9292
name: http
env:
- name: FOO
value: bar
- name: HELLO
value: world
livenessProbe:
httpGet:
port: http
path: /health/live
periodSeconds: 5
readinessProbe:
httpGet:
port: http
path: /health/ready
periodSeconds: 1
```
Now you can play with these endpoints. Let's make one Pod "not ready":
```bash
$ kubectl exec -ti healthcheck-demo-745554966d-f9jvz bash
www-data@healthcheck-demo-745554966d-f9jvz:/$ rm /tmp/ready
```
After 3 seconds you see that this Pod is not ready anymore (`0/1` in column `READY`):
```bash
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
healthcheck-demo-745554966d-f9jvz 0/1 Running 0 4m45s
healthcheck-demo-745554966d-ghxqk 1/1 Running 0 4m39s
healthcheck-demo-745554966d-xwhp5 1/1 Running 0 4m42s
```
Let's make it unhealthy now: delete the file `/tmp/live` inside the Pod:
```bash
$ kubectl exec -ti healthcheck-demo-745554966d-f9jvz bash
www-data@healthcheck-demo-745554966d-f9jvz:/$ rm /tmp/live
```
After around 15 seconds, Kubernetes will restart this Pod and everything is fine again:
```bash
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
healthcheck-demo-745554966d-f9jvz 1/1 Running 1 6m52s
healthcheck-demo-745554966d-ghxqk 1/1 Running 0 6m46s
healthcheck-demo-745554966d-xwhp5 1/1 Running 0 6m49s
```