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Registering Kubernetes Clusters using syncer
Syncer
1
How to register Kubernetes clusters using syncer

In order to register a Kubernetes clusters with the kcp server, users have to install a special component named syncer.

Requirements

Instructions

  1. (Optional) Skip this step, if you already have a physical cluster. Create a kind cluster to back the sync target:

    $ kind create cluster
Creating cluster "kind" ...
<snip>
Set kubectl context to "kind-kind"
You can now use your cluster with:

kubectl cluster-info --context kind-kind

{{% alert title="Note" color="primary" %}} This step sets current context to the new kind cluster. Make sure to use a KCP kubeconfig for the next steps unless told otherwise. {{% /alert %}}

  1. Create an organisation and immediately enter it:

    $ kubectl kcp workspace create my-org --enter
Workspace "my-org" (type root:organization) created. Waiting for it to be ready...
Workspace "my-org" (type root:organization) is ready to use.
Current workspace is "root:my-org" (type "root:organization").

  2. Enable the syncer for a p-cluster:

    kubectl kcp workload sync <synctarget name> --syncer-image <image name> -o syncer.yaml

    Where <image name> one of the syncer images for your corresponding KCP release (e.g. ghcr.io/kcp-dev/kcp/syncer:v0.7.5).

  3. Apply the manifest to the p-cluster:

    $ KUBECONFIG=<pcluster-config> kubectl apply -f syncer.yaml
namespace/kcp-syncer-kind-1owee1ci created
serviceaccount/kcp-syncer-kind-1owee1ci created
secret/kcp-syncer-kind-1owee1ci-token created
clusterrole.rbac.authorization.k8s.io/kcp-syncer-kind-1owee1ci created
clusterrolebinding.rbac.authorization.k8s.io/kcp-syncer-kind-1owee1ci created
secret/kcp-syncer-kind-1owee1ci created
deployment.apps/kcp-syncer-kind-1owee1ci created

    and it will create a kcp-syncer deployment:

    $ KUBECONFIG=<pcluster-config> kubectl -n kcp-syncer-kind-1owee1ci get deployments
NAME     READY   UP-TO-DATE   AVAILABLE   AGE
kcp-syncer   1/1     1            1           13m

  4. Wait for the kcp sync target to go ready:

    kubectl wait --for=condition=Ready synctarget/<mycluster>

Select resources to sync.

Syncer will by default use the kubernetes APIExport in root:compute workspace and sync deployments/services/ingresses to the physical cluster. The related API schemas of the physical cluster should be comptible with kubernetes 1.24. User can select to sync other resources in physical clusters or from other APIExports on kcp server.

To sync resources that the KCP server does not have an APIExport to support yet, run

kubectl kcp workload sync <mycluster> --syncer-image <image name> --resources foo.bar -o syncer.yaml

And apply the generated manifests to the physical cluster. The syncer will then import the API schema of foo.bar to the workspace of the synctarget, following up with an auto generated kubernetes APIExport/APIBinding in the same workspace. You can then create foo.bar in this workspace, or create an APIBinding in another workspace to bind this APIExport.

To sync resource from another existing APIExport in the KCP server, run

kubectl kcp workload sync <mycluster> --syncer-image <image name> --apiexports another-workspace:another-apiexport -o syncer.yaml

Syncer will start syncing the resources in this APIExport as long as the SyncTarget has compatible API schemas.

To see if a certain resource is supported to be synced by the syncer, you can check the state of the syncedResources in SyncTarget status.

Bind workspaces to the Location Workspace

After the SyncTarget is ready, switch to any workspace containing some workloads that you want to sync to this SyncTarget, and run

kubectl kcp bind compute <workspace of synctarget>

This command will create a Placement in the workspace. By default, it will also create APIBindings for global kubernetes APIExport and kubernetes APIExport in workspace of SyncTarget, if any of these APIExports are supported by the SyncTarget.

Alternatively, if you would like to bind other APIExports which are supported by the SyncerTarget, run:

kubectl kcp bind compute <workspace of synctarget> --apiexport <apiexport workspace>:<apiexport name>

In addition, you can specify the certain location or namespace to create placement. e.g.

kubectl kcp bind compute <workspace of synctarget> --location-selectors=env=test --namespace-selector=purpose=workload

this command will create a Placement selecting a Location with label env=test and bind the selected Location to namespaces with label purpose=workload. See more details of placement and location here

Running a workload

  1. Create a deployment:

    kubectl create deployment kuard --image gcr.io/kuar-demo/kuard-amd64:blue

{{% alert title="Note" color="primary" %}} Replace "gcr.io/kuar-demo/kuard-amd64:blue" with "gcr.io/kuar-demo/kuard-arm64:blue" in case you're running an Apple M1 based virtual machine. {{% /alert %}}

  1. Verify the deployment on the local workspace:

    $ kubectl rollout status deployment/kuard
Waiting for deployment "kuard" rollout to finish: 0 of 1 updated replicas are available...
deployment "kuard" successfully rolled out

For syncer development

Building components

The syncer, kcp and kubectl plugins should come from the same build, so they are compatible with each other.

To build, make the root kcp folder your current working directory and run:

make build-all install build-kind-images

If your go version is not 1.18, which is the expected version, you need to run

IGNORE_GO_VERSION=1 make build-all install build-kind-images

Make a note of the syncer image that is produced by this build, which is in the output near the end. It should be something like kind.local/syncer-c2e3073d5026a8f7f2c47a50c16bdbec:8287441974cf604dd93da5e6d010a78d38ae49733ea3a5031048a516101dd8a2. This will be used by the kubectl kcp workload sync ... command, below.

The kubectl kcp plugin binaries should be first in your path so kubectl picks them up.

which kubectl-kcp

should point to the kubectl-kcp you have just built in your $GOPATH/bin, and not any other installed version.

Start kcp on another terminal

kcp start

Running in a kind cluster with a local registry

You can run the syncer in a kind cluster for development.

  1. Create a kind cluster with a local registry to simplify syncer development by executing the following script:

    /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/kubernetes-sigs/kind/main/site/static/examples/kind-with-registry.sh)"

  2. From the kcp root directory:

    export KUBECONFIG=.kcp/admin.kubeconfig

  3. Create a location workspace and immediately enter it:

    $ kubectl kcp workspace create my-locations --enter
Workspace "my-locations" (type root:organization) created. Waiting for it to be ready...
Workspace "my-locations" (type root:organization) is ready to use.
Current workspace is "root:my-locations" (type "root:organization").

  4. To create the synctarget and use the image pushed to the local registry, supply <image name> to the kcp workload sync plugin command, where <image name> was captured in the build steps, above.

    kubectl kcp workload sync kind --syncer-image <image name> -o syncer.yaml

  5. Create a second workspace for your workloads and immediately enter it:

    $ kubectl kcp workspace ..
$ kubectl kcp workspace create my-workloads --enter
Workspace "my-workloads" (type root:organization) created. Waiting for it to be ready...
Workspace "my-workloads" (type root:organization) is ready to use.
Current workspace is "root:my-workloads" (type "root:organization").

  6. Bind it to the my-locations workspace with the synctarget:

    kubectl kcp bind compute "root:my-locations"

  7. Apply the manifest to the p-cluster:

    $ KUBECONFIG=<pcluster-config> kubectl apply -f syncer.yaml
namespace/kcp-syncer-kind-1owee1ci created
serviceaccount/kcp-syncer-kind-1owee1ci created
secret/kcp-syncer-kind-1owee1ci-token created
clusterrole.rbac.authorization.k8s.io/kcp-syncer-kind-1owee1ci created
clusterrolebinding.rbac.authorization.k8s.io/kcp-syncer-kind-1owee1ci created
secret/kcp-syncer-kind-1owee1ci created
deployment.apps/kcp-syncer-kind-1owee1ci created

    and it will create a kcp-syncer deployment:

    $ KUBECONFIG=<pcluster-config> kubectl -n kcp-syncer-kind-1owee1ci get deployments
NAME     READY   UP-TO-DATE   AVAILABLE   AGE
kcp-syncer   1/1     1            1           13m

  8. Wait for the kcp sync target to go ready:

    kubectl wait --for=condition=Ready synctarget/<mycluster>

  9. Add a deployment to the my-workloads workspace and check the p-cluster to see if the workload has been created there:

    kubectl create deployment --image=gcr.io/kuar-demo/kuard-amd64:blue --port=8080 kuard

Running locally

TODO(m1kola): we need a less hacky way to run locally: needs to be more close to what we have when running inside the kind with own kubeconfig.

This assumes that KCP is also being run locally.

  1. Create a kind cluster to back the sync target:

    $ kind create cluster
Creating cluster "kind" ...
<snip>
Set kubectl context to "kind-kind"
You can now use your cluster with:

kubectl cluster-info --context kind-kind

  2. Make sure to use kubeconfig for your local KCP:

    export KUBECONFIG=.kcp/admin.kubeconfig

  3. Create an organisation and immediately enter it:

    $ kubectl kcp workspace create my-org --enter
Workspace "my-org" (type root:organization) created. Waiting for it to be ready...
Workspace "my-org" (type root:organization) is ready to use.
Current workspace is "root:my-org" (type "root:organization").

  4. Enable the syncer for a p-cluster:

    kubectl kcp workload sync <mycluster> --syncer-image <image name> -o syncer.yaml

    <image name> can be anything here as it will only be used to generate syncer.yaml which we are not going to apply.

  5. Gather data required for the syncer:

    syncTargetName=<mycluster>
syncTargetUID=$(kubectl get synctarget $syncTargetName -o jsonpath="{.metadata.uid}")
fromCluster=$(kubectl ws current --short)

  6. Run the following snippet:

    go run ./cmd/syncer \
  --from-kubeconfig=.kcp/admin.kubeconfig \
  --from-context=base \
  --to-kubeconfig=$HOME/.kube/config \
  --sync-target-name=$syncTargetName \
  --sync-target-uid=$syncTargetUID \
  --from-cluster=$fromCluster \
  --resources=configmaps \
  --resources=deployments.apps \
  --resources=secrets \
  --resources=serviceaccounts \
  --qps=30 \
  --burst=20

  7. Wait for the kcp sync target to go ready:

    kubectl wait --for=condition=Ready synctarget/<mycluster>