Your App Is Alive

From the Kubernetes Colorado meetup on February 18th, 2016

1. Your App Is Alive Michelle Noorali Developer at Deis @michellenoorali
2. Health Checks
3. What?
4. a way to monitor your app’s health A Health Check is
5. Is your app… responsive?
6. Is your app… Performant?
7. Is your app… Stable?
8. What does it look like?
9. • /healthcheck or /healthz endpoint • checked by external system at intervals • On success, do nothing • On failure, notify and heal
10. In Kubernetes Land… •Health checks are built in! •But first…
11. Introducing Puffy • … a simple go web server
12. Let’s review! • I have an app (Puffy) and I want to deploy it onto my Kubernetes cluster so… • I write a manifest … • … which references an image • … which will contain all the instructions for my app
13. Key Concepts • Image • Union of layered filesystems • Immutable • Container (Docker, rkt) • runtime instance of an image
14. Kubernetes Concepts • Pod • Represents a logical application • One or more containers • Manifest • yaml file • serves as resource (ex. pod) definition • kubectl • CLI tool to control kubernetes cluster
15. Pre-requisites • Running Kubernetes cluster on GCE [Google Compute Engine] • Docker Image for app stored on DockerHub • DockerHub = place to store images • Can also use Quay.io or GCR [Google Container Registry]
16. Puffy Repo
17. Dockerfile
18. Makefile
19. Manifest file
20. Life of Puffy: The Skeleton • puffy starts out as an image • docker build -t mnoorali/puffy:1.0.0 . • docker push mnoorali/puffy:1.0.0
21. Demo: Create a Puffy Pod in Kubernetes Cluster
22. Life of Puffy: It’s Alive • create a pod definition in manifest • create resource in kubernetes from manifest • kubectl create -f puffy-pod.yaml • watch it come to life • kubectl get pods • Check it out • curl pod_ip:port/index on a node
23. Let’s make sure puffy is ok. • Here comes the health check part…
24. Two Probes walk into a coffeeshop… • Readiness Probe • Liveness Probe
25. Wait. What is this probe thing? • a probe = a diagnostic periodically performed on a container • Three ways to perform a diagnostic: • Execute a command in a container • Successful if exit status code 0 • Perform tcp check on a container’s IP address on a specific port • Successful if the port is open • Perform an HTTP Get against the container’s IP address on a specific port • Successful if response has status code >= 200 and <400
26. Back to the probes… • Readiness Probe • Is my app ready to serve traffic? • On failure, it stops serving requests • Liveness Probe • Is my app in a good state? • On failure, it restarts the pod
27. Define a Liveness Probe in the Pod Manifest
28. Apply the Changes in the Pod Manifest to the Cluster • kubectl delete -f puffy-pod.yaml • kubectl get pods • edit puffy-pod.yaml • kubectl create -f pod-puffy.yaml
29. FAIL • But, what happened?
30. Oops • forgot to add the /healthz endpoint • kubectl delete -f puffy-pod.yaml
31. Add /healthz • Define /healthz in app (common convention) • Re-build/re-tag image • Push image to registry • Edit image declaration in manifest
32. Bring Puffy Back! • kubectl create -f puffy-pod.yaml • kubectl get pods • kubectl describe pod puffy • On node, curl ip:port/healthz
33. Summary • automate monitoring apps with health checks • Use Kubernetes’s built in health check features • readinessProbe • Is your app ready to serve traffic? • livenessProbe • Is your app in a good state?
34. That’s it folks. Visit puffy at www.github.com/michelleN/puffy Will have a link to slides above and on twitter: @michellenoorali Thank You!