This PR removes the service mirror controller from `linkerd mc install` to `linkerd mc link`, as described in https://github.com/linkerd/rfc/pull/31. For fuller context, please see that RFC.
Basic multicluster functionality works here including:
* `linkerd mc install` installs the Link CRD but not any service mirror controllers
* `linkerd mc link` creates a Link resource and installs a service mirror controller which uses that Link
* The service mirror controller creates and manages mirror services, a gateway mirror, and their endpoints.
* The `linkerd mc gateways` command lists all linked target clusters, their liveliness, and probe latences.
* The `linkerd check` multicluster checks have been updated for the new architecture. Several checks have been rendered obsolete by the new architecture and have been removed.
The following are known issues requiring further work:
* the service mirror controller uses the existing `mirror.linkerd.io/gateway-name` and `mirror.linkerd.io/gateway-ns` annotations to select which services to mirror. it does not yet support configuring a label selector.
* an unlink command is needed for removing multicluster links: see https://github.com/linkerd/linkerd2/issues/4707
* an mc uninstall command is needed for uninstalling the multicluster addon: see https://github.com/linkerd/linkerd2/issues/4708
Signed-off-by: Alex Leong <alex@buoyant.io>
There are a few notable things happening in this PR:
- the probe manager has been decoupled from the cluster_watcher. Now its only responsibility is to watch for mirrored gateways beeing created and to probe them. This means that probes are initiated for all gateways no matter whether there are mirrored services being paired
- the number of paired services is derived from the existing services in the cluster rather than being published as a metric by the prober
- there are no events being exchanged between the cluster watcher and the probe manager
Signed-off-by: Zahari Dichev <zaharidichev@gmail.com>
Alex Leong
Zahari Dichev