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Now that we have a good number of longer exercises, it makes sense to rename the shorter demos/labs into 'labs' to avoid confusion between the two.
153 lines
3.5 KiB
Markdown
153 lines
3.5 KiB
Markdown
# Events
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- Kubernetes has an internal structured log of *events*
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- These events are ordinary resources:
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- we can view them with `kubectl get events`
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- they can be viewed and created through the Kubernetes API
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- they are stored in Kubernetes default database (e.g. etcd)
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- Most components will generate events to let us know what's going on
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- Events can be *related* to other resources
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---
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## Reading events
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- `kubectl get events` (or `kubectl get ev`)
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- Can use `--watch`
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⚠️ Looks like `tail -f`, but events aren't necessarily sorted!
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- Can use `--all-namespaces`
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- Cluster events (e.g. related to nodes) are in the `default` namespace
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- Viewing all "non-normal" events:
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```bash
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kubectl get ev -A --field-selector=type!=Normal
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```
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(as of Kubernetes 1.19, `type` can be either `Normal` or `Warning`)
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---
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## Reading events (take 2)
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- When we use `kubectl describe` on an object, `kubectl` retrieves the associated events
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.lab[
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- See the API requests happening when we use `kubectl describe`:
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```bash
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kubectl describe service kubernetes --namespace=default -v6 >/dev/null
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```
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]
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---
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## Generating events
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- This is rarely (if ever) done manually
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(i.e. by crafting some YAML)
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- But controllers (e.g. operators) need this!
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- It's not mandatory, but it helps with *operability*
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(e.g. when we `kubectl describe` a CRD, we will see associated events)
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---
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## ⚠️ Work in progress
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- "Events" can be :
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- "old-style" events (in core API group, aka `v1`)
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- "new-style" events (in API group `events.k8s.io`)
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- See [KEP 383](https://github.com/kubernetes/enhancements/blob/master/keps/sig-instrumentation/383-new-event-api-ga-graduation/README.md) in particular this [comparison between old and new APIs](https://github.com/kubernetes/enhancements/blob/master/keps/sig-instrumentation/383-new-event-api-ga-graduation/README.md#comparison-between-old-and-new-apis)
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---
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## Experimenting with events
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- Let's create an event related to a Node, based on @@LINK[k8s/event-node.yaml]
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.lab[
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- Edit `k8s/event-node.yaml`
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- Update the `name` and `uid` of the `involvedObject`
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- Create the event with `kubectl create -f`
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- Look at the Node with `kubectl describe`
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]
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---
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## Experimenting with events
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- Let's create an event related to a Pod, based on @@LINK[k8s/event-pod.yaml]
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.lab[
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- Create a pod
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- Edit `k8s/event-pod.yaml`
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- Edit the `involvedObject` section (don't forget the `uid`)
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- Create the event with `kubectl create -f`
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- Look at the Pod with `kubectl describe`
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]
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---
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## Generating events in practice
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- In Go, use an `EventRecorder` provided by the `kubernetes/client-go` library
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- [EventRecorder interface](https://github.com/kubernetes/client-go/blob/release-1.19/tools/record/event.go#L87)
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- [kubebuilder book example](https://book-v1.book.kubebuilder.io/beyond_basics/creating_events.html)
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- It will take care of formatting / aggregating events
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- To get an idea of what to put in the `reason` field, check [kubelet events](
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https://github.com/kubernetes/kubernetes/blob/release-1.19/pkg/kubelet/events/event.go)
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---
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## Cluster operator perspective
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- Events are kept 1 hour by default
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- This can be changed with the `--event-ttl` flag on the API server
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- On very busy clusters, events can be kept on a separate etcd cluster
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- This is done with the `--etcd-servers-overrides` flag on the API server
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- Example:
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```
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--etcd-servers-overrides=/events#http://127.0.0.1:12379
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```
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???
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:EN:- Consuming and generating cluster events
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:FR:- Suivre l'activité du cluster avec les *events*
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