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The commands to install Stern and Helm aren't super exciting, so let's pre-install these tools. That way, we also generate completion for them. We still give installation instructions just in case, but this saves time for more important stuff.
238 lines
4.6 KiB
Markdown
238 lines
4.6 KiB
Markdown
# Managing stacks with Helm
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- We created our first resources with `kubectl run`, `kubectl expose` ...
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- We have also created resources by loading YAML files with `kubectl apply -f`
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- For larger stacks, managing thousands of lines of YAML is unreasonable
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- These YAML bundles need to be customized with variable parameters
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(E.g.: number of replicas, image version to use ...)
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- It would be nice to have an organized, versioned collection of bundles
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- It would be nice to be able to upgrade/rollback these bundles carefully
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- [Helm](https://helm.sh/) is an open source project offering all these things!
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---
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## Helm concepts
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- `helm` is a CLI tool
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- `tiller` is its companion server-side component
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- A "chart" is an archive containing templatized YAML bundles
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- Charts are versioned
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- Charts can be stored on private or public repositories
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---
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## Installing Helm
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- If the `helm` CLI is not installed in your environment, install it
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.exercise[
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- Check if `helm` is installed:
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```bash
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helm
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```
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- If it's not installed, run the following command:
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```bash
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curl https://raw.githubusercontent.com/kubernetes/helm/master/scripts/get | bash
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```
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]
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---
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## Installing Tiller
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- Tiller is composed of a *service* and a *deployment* in the `kube-system` namespace
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- They can be managed (installed, upgraded...) with the `helm` CLI
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.exercise[
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- Deploy Tiller:
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```bash
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helm init
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```
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]
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If Tiller was already installed, don't worry: this won't break it.
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At the end of the install process, you will see:
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```
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Happy Helming!
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```
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---
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## Fix account permissions
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- Helm permission model requires us to tweak permissions
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- In a more realistic deployment, you might create per-user or per-team
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service accounts, roles, and role bindings
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.exercise[
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- Grant `cluster-admin` role to `kube-system:default` service account:
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```bash
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kubectl create clusterrolebinding add-on-cluster-admin \
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--clusterrole=cluster-admin --serviceaccount=kube-system:default
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```
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]
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(Defining the exact roles and permissions on your cluster requires
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a deeper knowledge of Kubernetes' RBAC model. The command above is
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fine for personal and development clusters.)
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---
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## View available charts
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- A public repo is pre-configured when installing Helm
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- We can view available charts with `helm search` (and an optional keyword)
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.exercise[
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- View all available charts:
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```bash
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helm search
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```
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- View charts related to `prometheus`:
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```bash
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helm search prometheus
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```
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]
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---
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## Install a chart
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- Most charts use `LoadBalancer` service types by default
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- Most charts require persistent volumes to store data
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- We need to relax these requirements a bit
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.exercise[
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- Install the Prometheus metrics collector on our cluster:
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```bash
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helm install stable/prometheus \
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--set server.service.type=NodePort \
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--set server.persistentVolume.enabled=false
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```
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]
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Where do these `--set` options come from?
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---
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## Inspecting a chart
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- `helm inspect` shows details about a chart (including available options)
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.exercise[
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- See the metadata and all available options for `stable/prometheus`:
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```bash
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helm inspect stable/prometheus
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```
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]
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The chart's metadata includes an URL to the project's home page.
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(Sometimes it conveniently points to the documentation for the chart.)
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---
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## Creating a chart
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- We are going to show a way to create a *very simplified* chart
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- In a real chart, *lots of things* would be templatized
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(Resource names, service types, number of replicas...)
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.exercise[
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- Create a sample chart:
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```bash
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helm create dockercoins
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```
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- Move away the sample templates and create an empty template directory:
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```bash
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mv dockercoins/templates dockercoins/default-templates
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mkdir dockercoins/templates
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```
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]
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---
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## Exporting the YAML for our application
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- The following section assumes that DockerCoins is currently running
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.exercise[
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- Create one YAML file for each resource that we need:
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.small[
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```bash
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while read kind name; do
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kubectl get -o yaml --export $kind $name > dockercoins/templates/$name-$kind.yaml
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done <<EOF
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deployment worker
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deployment hasher
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daemonset rng
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deployment webui
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deployment redis
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service hasher
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service rng
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service webui
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service redis
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EOF
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```
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]
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]
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---
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## Testing our helm chart
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.exercise[
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- Let's install our helm chart! (`dockercoins` is the path to the chart)
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```bash
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helm install dockercoins
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```
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]
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--
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- Since the application is already deployed, this will fail:<br>
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`Error: release loitering-otter failed: services "hasher" already exists`
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- To avoid naming conflicts, we will deploy the application in another *namespace*
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