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https://github.com/squat/service-reflector

Service-Reflector mirrors Kubernetes Services so that Pods in one cluster can natively access Services in another
https://github.com/squat/service-reflector

federation kubernetes multi-cluster networking service-reflector

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Service-Reflector mirrors Kubernetes Services so that Pods in one cluster can natively access Services in another

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# Service-Reflector



Service-Reflector mirrors Kubernetes Services so that Pods running in one cluster can natively access Services from another cluster.



[![Build Status](https://travis-ci.org/squat/service-reflector.svg?branch=master)](https://travis-ci.org/squat/service-reflector)

[![Go Report Card](https://goreportcard.com/badge/github.com/squat/service-reflector)](https://goreportcard.com/report/github.com/squat/service-reflector)



## Overview



A key use for multi-cluster Kubernetes is to allow Pods and Services in one cluster to access those running in another cluster.

However, a Pod in cluster A has no Kubernetes-native way of discovering a Service in cluster B or determining its endpoints; instead it must be pointed explicitly at the Service's ClusterIP.

One solution to this issue is for an administrator to create a Service in cluster A to mirror the one in cluster B with Endpoints that point at the Service’s Pods.

Service-Reflector automates the mirroring of selected Services from one cluster to another to simplify running multi-cluster Kubernetes.



## How it works



Service-Reflector is comprised of two components: a Reflector and an Emitter.

Both components are run by default, though either can be run independently or disabled, via the `--reflector` and `--emitter` flags.



### Reflector



The Reflector is a controller that watches source APIs for Services to reflect and creates mirror Services and Endpoints in the host cluster.

One Reflector can watch many sources for Services, allowing a cluster to access Services from many different clusters.

The source APIs can be any Kubernetes-style API that allows listing and watching Services and Endpoints, for example:

* a Kubernetes apiserver, specified with the `--reflector.source-kubeconfig` flag; or

* an Emitter, specified with the `--reflector.source-api` flag.



### Emitter



In order allow a Reflector in cluster A to find Services in cluster B, we must point the Reflector at a source API, namely cluster B's Kubernetes apiserver.

Doing so requires configuring the Reflector with a Kubeconfig or ServiceAccount token from cluster B.

To simplify deployment, Service-Reflector provides an Emitter, a Kubernetes-style apiserver that implements only the list and watch verbs for Services and Endpoints.

The only details a Reflector needs to access an Emitter's API is the Emitter's URL.

Furthermore, the Emitter allows an administrator to specify a selector to limit which Services are exposed to the Reflector; this is done via the `--emitter.selector` flag.



## Installing on Kubernetes



### Step 1: connect Kubernetes clusters



Start by connecting two or more Kubernetes clusters with the desired multi-cluster solution, e.g. [Kilo](https://github.com/squat/kilo).

The Service CIDR and Pod CIDR of each cluster must be routable from the others.



### Step 2: install Service-Reflector!



Service-Reflector can be installed on any Kubernetes cluster by deploying a Deployment:



```shell

kubectl apply -f https://raw.githubusercontent.com/squat/service-reflector/master/manifests/service-reflector.yaml

```



### Step 3: specify source APIs



In order for the Reflector to find Services to mirror, it must be configured with a source API.

The following snippet could be used to configure Service-Reflectors in two clusters:



```shell

# Register the emitter in cluster1 as a source of the reflector in cluster2.

cat <