Merge pull request #480 from jpetazzo/make-chart

Add a more meaningful exercise with Helm charts

slides/k8s/create-more-charts.md

@@ -0,0 +1,367 @@
+# Creating Helm charts
+
+- We are going to create a generic Helm chart
+
+- We will use that Helm chart to deploy DockerCoins
+
+- Each component of DockerCoins will have its own *release*
+
+- In other words, we will "install" that Helm chart multiple times
+
+  (one time per component of DockerCoins)
+
+---
+
+## Creating a generic chart
+
+- Rather than starting from scratch, we will use `helm create`
+
+- This will give us a basic chart that we will customize
+
+.exercise[
+
+- Create a basic chart:
+  ```bash
+  cd ~
+  helm create helmcoins
+  ```
+
+]
+
+This creates a basic chart in the directory `helmcoins`.
+
+---
+
+## What's in the basic chart?
+
+- The basic chart will create a Deployment and a Service
+
+- Optionally, it will also include an Ingress
+
+- If we don't pass any values, it will deploy the `nginx` image
+
+- We can override many things in that chart
+
+- Let's try to deploy DockerCoins components with that chart!
+
+---
+
+## Writing `values.yaml` for our components
+
+- We need to write one `values.yaml` file for each component
+
+  (hasher, redis, rng, webui, worker)
+
+- We will start with the `values.yaml` of the chart, and remove what we don't need
+
+- We will create 5 files:
+
+  hasher.yaml, redis.yaml, rng.yaml, webui.yaml, worker.yaml
+
+---
+
+## Getting started
+
+- For component X, we want to use the image dockercoins/X:v0.1
+
+  (for instance, for rng, we want to use the image dockercoins/rng:v0.1)
+
+- Exception: for redis, we want to use the official image redis:latest
+
+.exercise[
+
+- Write minimal YAML files for the 5 components, specifying only the image
+
+]
+
+--
+
+*Hint: our YAML files should look like this.*
+
+```yaml
+### rng.yaml
+image:
+  repository: dockercoins/`rng`
+  tag: v0.1
+```
+
+---
+
+## Deploying DockerCoins components
+
+- For convenience, let's work in a separate namespace
+
+.exercise[
+
+- Create a new namespace:
+  ```bash
+  kubectl create namespace helmcoins
+  ```
+
+- Switch to that namespace:
+  ```bash
+  kns helmcoins
+  ```
+
+]
+
+---
+
+## Deploying the chart
+
+- To install a chart, we can use the following command:
+  ```bash
+  helm install [--name `X`] <chart>
+  ```
+
+- We can also use the following command, which is idempotent:
+  ```bash
+  helm upgrade --install `X` chart
+  ```
+
+.exercise[
+
+- Install the 5 components of DockerCoins:
+  ```bash
+    for COMPONENT in hasher redis rng webui worker; do
+      helm upgrade --install $COMPONENT helmcoins/ --values=$COMPONENT.yaml
+    done
+  ```
+
+]
+
+---
+
+## Checking what we've done
+
+- Let's see if DockerCoins is working!
+
+.exercise[
+
+- Check the logs of the worker:
+  ```bash
+  stern worker
+  ```
+
+- Look at the resources that were created:
+  ```bash
+  kubectl get all
+  ```
+
+]
+
+There are *many* issues to fix!
+
+---
+
+## Service names
+
+- Our services should be named `rng`, `hasher`, etc., but they are named differently
+
+- Look at the YAML template used for the services
+
+- Does it look like we can override the name of the services?
+
+--
+
+- *Yes*, we can use `.Values.nameOverride`
+
+- This means setting `nameOverride` in the values YAML file
+
+---
+
+## Setting service names
+
+- Let's add `nameOverride: X` in each values YAML file!
+
+  (where X is hasher, redis, rng, etc.)
+
+.exercise[
+
+- Edit the 5 YAML files to add `nameOverride: X`
+
+- Deploy the updated Chart:
+  ```bash
+    for COMPONENT in hasher redis rng webui worker; do
+      helm upgrade --install $COMPONENT helmcoins/ --values=$COMPONENT.yaml
+    done
+  ```
+  (Yes, this is exactly the same command as before!)
+
+]
+
+---
+
+## Checking what we've done
+
+.exercise[
+
+- Check the service names:
+  ```bash
+  kubectl get services
+  ```
+  Great! (We have a useless service for `worker`, but let's ignore it for now.)
+
+- Check the state of the pods:
+  ```bash
+  kubectl get pods
+  ```
+  Not so great... Some pods are *not ready.*
+
+]
+
+---
+
+## Troubleshooting pods
+
+- The easiest way to troubleshoot pods is to look at *events*
+
+- We can look at all the events on the cluster (with `kubectl get events`)
+
+- Or we can use `kubectl describe` on the objects that have problems
+
+  (`kubectl describe` will retrieve the events related to the object)
+
+.exercise[
+
+- Check the events for the redis pods:
+  ```bash
+  kubectl describe pod -l app.kubernetes.io/name=redis
+  ```
+
+]
+
+What's going on?
+
+---
+
+## Healthchecks
+
+- The default chart defines healthchecks doing HTTP requests on port 80
+
+- That won't work for redis and worker
+
+  (redis is not HTTP, and not on port 80; worker doesn't even listen)
+
+--
+
+- We could comment out the healthchecks
+
+- We could also make them conditional
+
+- This sounds more interesting, let's do that!
+
+---
+
+## Conditionals
+
+- We need to enclose the healthcheck block with:
+
+  `{{ if CONDITION }}` at the beginning
+
+  `{{ end }}` at the end
+
+- For the condition, we will use `.Values.healthcheck`
+
+---
+
+## Updating the deployment template
+
+.exercise[
+
+- Edit `helmcoins/templates/deployment.yaml`
+
+- Before the healthchecks section (it starts with `livenessProbe:`), add:
+
+  `{{ if .Values.healthcheck }}`
+
+- After the healthchecks section (just before `resources:`), add:
+
+  `{{ end }}`
+
+- Edit `hasher.yaml`, `rng.yaml`, `webui.yaml` to add:
+
+  `healthcheck: true`
+
+]
+
+---
+
+## Update the deployed charts
+
+- We can now apply the new templates (and the new values)
+
+.exercise[
+
+- Use the same command as earlier to upgrade all five components
+
+- Use `kubectl describe` to confirm that `redis` starts correctly
+
+- Use `kubectl describe` to confirm that `hasher` still has healthchecks
+
+]
+
+---
+
+## Is it working now?
+
+- If we look at the worker logs, it appears that the worker is still stuck
+
+- What could be happening?
+
+--
+
+- The redis service is not on port 80!
+
+- We need to update the port number in redis.yaml
+
+- We also need to update the port number in deployment.yaml
+
+  (it is hard-coded to 80 there)
+
+---
+
+## Setting the redis port
+
+.exercise[
+
+- Edit `redis.yaml` to add:
+  ```yaml
+    service:
+      port: 6379
+  ```
+
+- Edit `helmcoins/templates/deployment.yaml`
+
+- The line with `containerPort` should be:
+  ```yaml
+  containerPort: {{ .Values.service.port }}
+  ```
+
+]
+
+---
+
+## Apply changes
+
+- Re-run the for loop to execute `helm upgrade` one more time
+
+- Check the worker logs
+
+- This time, it should be working!
+
+---
+
+## Extra steps
+
+- We don't need to create a service for the worker
+
+- We can put the whole service block in a conditional
+
+  (this will require additional changes in other files referencing the service)
+
+- We can set the webui to be a NodePort service
+
+- We can change the number of workers with `replicaCount`
+
+- And much more!