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docs: fix broken links (CI) #3514

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Jul 24, 2020
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docs: fix broken links (CI) #3514

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5417faa
docs: remove leader sdk implementation that is no longer supported - …
Jul 24, 2020
532de02
doc: fix link for leader election
Jul 24, 2020
cc28f73
doc: fix link for leader election
Jul 24, 2020
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48 changes: 15 additions & 33 deletions website/content/en/docs/building-operators/golang/advanced-topics.md
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Original file line number Diff line number Diff line change
Expand Up @@ -28,7 +28,14 @@ type MyAppStatus struct {
}
```

<!-- todo(camilamacedo)
the following link was comment for do no broke the CI
this impl probably will came from operator-lib
however, we also need to check if we would not like to just let them use
https://github.com/kubernetes/kubernetes/pull/92717/files
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pkg/status was also moved to operator-lib. Let's just update that link as well.

And I don't think this is the appropriate place for a comment about the choice of implementations to use.

I think a better choice would be to open an issue in operator-lib asking whether it makes sense to deprecate status and point users to k8s.io/apimachinery's implementation.


Then, in your controller, you can use [`Conditions`][godoc-conditions] methods to make it easier to set and remove conditions or check their current values.
-->

### Adding 3rd Party Resources To Your Operator

Expand Down Expand Up @@ -231,38 +238,7 @@ func contains(list []string, s string) bool {
During the lifecycle of an operator it's possible that there may be more than 1 instance running at any given time e.g when rolling out an upgrade for the operator.
In such a scenario it is necessary to avoid contention between multiple operator instances via leader election so that only one leader instance handles the reconciliation while the other instances are inactive but ready to take over when the leader steps down.

There are two different leader election implementations to choose from, each with its own tradeoff.
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just removed the part of the sdk impl and all the rest of the texts were kept in the same way.


- [Leader-with-lease][leader_with_lease]: The leader pod periodically renews the leader lease and gives up leadership when it can't renew the lease. This implementation allows for a faster transition to a new leader when the existing leader is isolated, but there is a possibility of split brain in [certain situations][lease_split_brain].
- [Leader-for-life][leader_for_life]: The leader pod only gives up leadership (via garbage collection) when it is deleted. This implementation precludes the possibility of 2 instances mistakenly running as leaders (split brain). However, this method can be subject to a delay in electing a new leader. For instance when the leader pod is on an unresponsive or partitioned node, the [`pod-eviction-timeout`][pod_eviction_timeout] dictates how long it takes for the leader pod to be deleted from the node and step down (default 5m).

By default the SDK enables the leader-with-lease implementation. However you should consult the docs above for both approaches to consider the tradeoffs that make sense for your use case.

The following examples illustrate how to use the two options:

#### Leader for life

A call to `leader.Become()` will block the operator as it retries until it can become the leader by creating the configmap named `memcached-operator-lock`.

```Go
import (
...
"github.com/operator-framework/operator-sdk/pkg/leader"
)

func main() {
...
err = leader.Become(context.TODO(), "memcached-operator-lock")
if err != nil {
log.Error(err, "Failed to retry for leader lock")
os.Exit(1)
}
...
}
```
If the operator is not running inside a cluster `leader.Become()` will simply return without error to skip the leader election since it can't detect the operator's namespace.

#### Leader with lease
By default the SDK enables the [Leader-with-lease][leader_with_lease] implementation. The leader pod periodically renews the leader lease and gives up leadership when it can't renew the lease. This implementation allows for a faster transition to a new leader when the existing leader is isolated, but there is a possibility of split brain in [certain situations][lease_split_brain].

The leader-with-lease approach can be enabled via the [Manager Options][manager_options] for leader election.

Expand All @@ -287,14 +263,20 @@ func main() {
When the operator is not running in a cluster, the Manager will return an error on starting since it can't detect the operator's namespace in order to create the configmap for leader election. You can override this namespace by setting the Manager's `LeaderElectionNamespace` option.

[typical-status-properties]: https://github.com/kubernetes/community/blob/master/contributors/devel/sig-architecture/api-conventions.md#typical-status-properties

<!-- todo(camilamacedo)
the following link was comment for do no broke the CI
this impl probably will came from operator-lib
however, we also need to check if we would not like to just let them use
https://github.com/kubernetes/kubernetes/pull/92717/files
[godoc-conditions]: https://godoc.org/github.com/operator-framework/operator-sdk/pkg/status#Conditions
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this one is falling now. I am not sure if we will still providing or not the helper in via operator-lib so just comment and raised : #3515

-->
[scheme_package]:https://github.com/kubernetes/client-go/blob/master/kubernetes/scheme/register.go
[deployments_register]: https://github.com/kubernetes/api/blob/master/apps/v1/register.go#L41
[runtime_package]: https://godoc.org/k8s.io/apimachinery/pkg/runtime
[scheme_builder]: https://godoc.org/sigs.k8s.io/controller-runtime/pkg/scheme#Builder
[metrics_doc]: https://book.kubebuilder.io/reference/metrics.html
[lease_split_brain]: https://github.com/kubernetes/client-go/blob/30b06a83d67458700a5378239df6b96948cb9160/tools/leaderelection/leaderelection.go#L21-L24
[leader_for_life]: https://godoc.org/github.com/operator-framework/operator-sdk/pkg/leader
[leader_with_lease]: https://godoc.org/github.com/kubernetes-sigs/controller-runtime/pkg/leaderelection
[pod_eviction_timeout]: https://kubernetes.io/docs/reference/command-line-tools-reference/kube-controller-manager/#options
[manager_options]: https://godoc.org/github.com/kubernetes-sigs/controller-runtime/pkg/manager#Options