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@@ -5,32 +5,43 @@ This enables clusters to provide services to other clusters over a secure connec
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For example, a cluster on AWS with access to GPUs could run a machine learning service that could be consumed by workloads running in a another location, e.g. an on-prem cluster without GPUs.
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Unlike services exposed via Ingresses or NodePort Services, multi-cluster services can remain private and internal to the clusters.
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-*Note*: clusters connected with Kilo must have non-overlapping pod and service CIDRs.
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+*Note*: in order for connected clusters to be fully routable, the allowed IPs that they declare must be non-overlapping, i.e. the Kilo, pod, and service CIDRs.
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+
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+## Getting Started
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Consider two clusters, `cluster1` with:
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-* kubeconfig: `KUBECONFIG1`
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-* pod CIDR: `$PODCIDR1`
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+* kubeconfig: `KUBECONFIG1`; and
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* service CIDR: `$SERVICECIDR1`
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-* a node named: `$NODE1`
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and `cluster2` with:
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* kubeconfig: `KUBECONFIG2`
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-* pod CIDR: `$PODCIDR2`
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-* service CIDR: `$SERVICECIDR2`
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-* a node named: `$NODE2`
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+* service CIDR: `$SERVICECIDR2`; and
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In order to give `cluster2` access to a service running on `cluster1`, start by peering the nodes:
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```shell
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-# Register cluster1 as a peer of cluster2.
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-kgctl --kubeconfig $KUBECONFIG1 showconf node $NODE1 --as-peer -o yaml --allowed-ips $PODCIDR1,$SERVICECIDR1 | kubectl --kubeconfig KUBECONFIG2 apply -f -
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-# Register cluster2 as a peer of cluster1.
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-kgctl --kubeconfig $KUBECONFIG2 showconf node $NODE2 --as-peer -o yaml --allowed-ips $PODCIDR2,$SERVICECIDR2 | kubectl --kubeconfig KUBECONFIG1 apply -f -
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+# Register the nodes in cluster1 as peers of cluster2.
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+for n in $(kubectl --kubeconfig $KUBECONFIG1 get no -o name | cut -d'/' -f2); do
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+ # Specify the service CIDR as an extra IP range that should be routable.
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+ kgctl --kubeconfig $KUBECONFIG1 showconf node $n --as-peer -o yaml --allowed-ips $SERVICECIDR1 | kubectl --kubeconfig KUBECONFIG2 apply -f -
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+done
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+# Register the nodes in cluster2 as peers of cluster1.
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+for n in $(kubectl --kubeconfig $KUBECONFIG2 get no -o name | cut -d'/' -f2); do
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+ # Specify the service CIDR as an extra IP range that should be routable.
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+ kgctl --kubeconfig $KUBECONFIG2 showconf node $n --as-peer -o yaml --allowed-ips $SERVICECIDR2 | kubectl --kubeconfig KUBECONFIG1 apply -f -
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+done
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```
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-Now, `cluster2` has access to Pods and Services on `cluster1`, and vice-versa.
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-However, as it stands the external Services can only be accessed by using their clusterIPs directly; in other words, they are not Kubernetes-native.
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-We can change that by creating a Kubernetes Service in `cluster2` to mirror the Service in `cluster1`:
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+Now, Pods on `cluster1` can ping, cURL, or otherwise make requests against Pods and Servives in `cluster2` and vice-versa.
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+
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+## Mirroring Services
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+
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+At this point, Kilo has created a fully routable network between the two clusters.
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+However, as it stands the external Services can only be accessed by using their clusterIPs directly.
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+For example, a Pod in `cluster2` would need to use the URL `http://$CLUSTERIP_FROM_CLUSTER1` to make a request against a Service running in `cluster1`.
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+In other words, the Services are not yet Kubernetes-native.
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+
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+We can easily change that by creating a Kubernetes Service in `cluster2` to mirror the Service in `cluster1`:
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```shell
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cat <<'EOF' | kubectl --kubeconfig $KUBECONFIG2 apply -f -
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@@ -48,10 +59,11 @@ metadata:
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name: important-service
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subsets:
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- addresses:
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- - ip: $CLUSTERIP # The cluster IP of the important service on cluster1.
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+ - ip: $CLUSTERIP_FROM_CLUSTER1 # The cluster IP of the important service on cluster1.
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ports:
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- port: 80
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EOF
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```
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Now, `important-service` can be used on `cluster2` just like any other Kubernetes Service.
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+That means that a Pod in `cluster2` could directly use the Kubernetes DNS name for the Service when making HTTP requests, for example: `http://important-service.default.svc.cluster.local`.
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