Add rolling upgrade section and whatsnext

docs/kube.yml

@@ -72,6 +72,8 @@ chapters:
   - ourapponkube.md
 - - kubectlscale.md
   - daemonset.md
+  - rollout.md
+  - whatsnext.md
 - |
   class: title
 

docs/rollout.md

@@ -0,0 +1,197 @@
+# Rolling updates
+
+- By default (without rolling updates), when a scaled resource is updated:
+
+  - new pods are created
+
+  - old pods are terminated
+  
+  - ... all at the same time
+  
+  - if something goes wrong, ¯\\\_(ツ)\_/¯
+
+---
+
+# Rolling updates
+
+- With rolling updates, when a resource is updated, it happens progressively
+
+- Two parameters determine the pace of the rollout: `maxUnavailable` and `maxSurge`
+
+- They can be specified in absolute number of pods, or percentage of the `replicas` count
+
+- At any given time ...
+
+  - there will always be at least `replicas`-`maxUnavailable` pods available
+
+  - there will never be more than `replicas`+`maxSurge` pods in total
+
+  - there will therefore be up to `maxUnavailable`+`maxSurge` pods being updated
+
+- We have the possibility to rollback to the previous version
+  <br/>(if the update fails or is unsatisfactory in any way)
+
+---
+
+## Rolling updates in practice
+
+- As of Kubernetes 1.8, we can do rolling updates with:
+
+  `deployments`, `daemonsets`, `statefulsets`
+
+- Editing one of these resources will automatically result in a rolling update
+
+- Rolling updates can be monitored with the `kubectl rollout` subcommand
+
+---
+
+## Building a new version of the `worker` service
+
+.exercise[
+
+- Go to the `stack` directory:
+  ```bash
+  cd ~/orchestration-workshop/stacks
+  ```
+
+- Edit `dockercoins/worker/worker.py`, update the `sleep` line to sleep 1 second
+
+- Build a new tag and push it to the registry:
+  ```bash
+  export REGISTRY=localhost:3xxxx TAG=v0.2
+  docker-compose -f dockercoins.yml build
+  docker-compose -f dockercoins.yml push
+  ```
+
+]
+
+---
+
+## Rolling out the new version of the `worker` service
+
+.exercise[
+
+- Let's monitor what's going on by opening a few terminals, and run:
+  ```bash
+  kubectl get pods -w
+  kubectl get replicasets -w
+  kubectl get deployments -w
+  ```
+
+- Update `worker` either with `kubectl edit`, or by running:
+  ```bash
+  kubectl set image deploy worker worker=$REGISTRY/worker:$TAG
+  ```
+
+]
+
+--
+
+That rollout should be pretty quick. What shows in the web UI?
+
+---
+
+## Rolling out a boo-boo
+
+- What happens if we make a mistake?
+
+.exercise[
+
+- Update `worker` by specifying a non-existent image:
+  ```bash
+  export TAG=v0.3
+  kubectl set image deploy worker worker=$REGISTRY/worker:$TAG
+  ```
+
+- Check what's going on:
+  ```bash
+  kubectl rollout status deploy worker
+  ```
+
+]
+
+--
+
+Our rollout is stuck. However, the app is not dead (just 10% slower).
+
+---
+
+## Recovering from a bad rollout
+
+- We could push some `v0.3` image
+
+  (the pod retry logic will eventually catch it and the rollout will proceed)
+
+- Or we could invoke a manual rollback
+
+.exercise[
+
+- Cancel the deployment and wait for the dust to settle down:
+  ```bash
+  kubectl rollout undo deploy worker
+  kubectl rollout status deploy worker
+  ```
+
+]
+
+---
+
+## Changing rollout parameters
+
+- We want to:
+
+  - revert to `v0.1`
+  - be conservative on availability (always have desired number of available workers)
+  - be aggressive on rollout speed (update more than one pod at a time) 
+  - give some time to our workers to "warm up" before starting more
+
+The corresponding changes can be expressed in the following YAML snippet:
+
+.small[
+```yaml
+spec:
+  template:
+    spec:
+      containers:
+      - name: worker
+        image: $REGISTRY/worker:v0.1
+  strategy:
+    rollingUpdate:
+      maxUnavailable: 0
+      maxSurge: 3
+  minReadySeconds: 10
+```
+]
+
+---
+
+## Applying changes through a YAML patch
+
+- We could use `kubectl edit deployment worker`
+
+- But we could also use `kubectl patch` with the exact YAML shown before
+
+.exercise[
+
+.small[
+
+- Apply all our changes and wait for them to take effect:
+  ```bash
+  kubectl patch deployment worker -p "
+    spec:
+      template:
+        spec:
+          containers:
+          - name: worker
+            image: $REGISTRY/worker:v0.1
+      strategy:
+        rollingUpdate:
+          maxUnavailable: 0
+          maxSurge: 3
+      minReadySeconds: 10
+    "
+  kubectl rollout status deployment worker
+  ```
+  ] 
+
+]

docs/whatsnext.md

@@ -0,0 +1,17 @@
+## What's next?
+
+- Stateful services (databases and the like)
+
+  volumes, persistent volume claims, stateful sets
+
+- Layer 7 constructs (HTTP routing)
+
+  ingress (check traefik!)
+
+- Logging, metrics
+
+- Secrets, config maps
+
+- Developer experience
+
+- Dashboard