Ocelot/docs/features/kubernetes.rst

Kubernetes
==============

This feature was requested as part of `Issue 345 <https://github.com/ThreeMammals/Ocelot/issues/345>`_ . to add support for kubernetes's service discovery provider. 

The first thing you need to do is install the NuGet package that provides kubernetes support in Ocelot.

``Install-Package Ocelot.Provider.Kubernetes``

Then add the following to your ConfigureServices method.

.. code-block:: csharp

    s.AddOcelot()
     .AddKubernetes();

If you have services deployed in kubernetes you will normally use the naming service to access them. Default usePodServiceAccount = True, which means that ServiceAccount using Pod to access the service of the k8s cluster needs to be ServiceAccount based on RABC authorization

.. code-block::csharp
    public static class OcelotBuilderExtensions
    {
        public static IOcelotBuilder AddKubernetes(this IOcelotBuilder builder, bool usePodServiceAccount = true);
    }

You can replicate a Permissive. Using RBAC role bindings.
`Permissive RBAC Permissions <https://kubernetes.io/docs/reference/access-authn-authz/rbac/#permissive-rbac-permissions>`_, k8s api server and token will read from pod .

.. code-block::json
kubectl create clusterrolebinding permissive-binding  --clusterrole=cluster-admin  --user=admin  --user=kubelet --group=system:serviceaccounts

The following example shows how to set up a ReRoute that will work in kubernetes. The most important thing is the ServiceName which is made up of the 
kubernetes service name. We also need to set up the ServiceDiscoveryProvider in GlobalConfiguration. The example here shows a typical configuration. 


.. code-block:: json

    {
  "ReRoutes": [
    {
      "DownstreamPathTemplate": "/api/values",
      "DownstreamScheme": "http",
      "UpstreamPathTemplate": "/values",
      "ServiceName": "downstreamservice",
      "UpstreamHttpMethod": [ "Get" ]     
    }
  ],
  "GlobalConfiguration": {
    "ServiceDiscoveryProvider": {
      "Host": "192.168.0.13",
      "Port": 443,
      "Token": "txpc696iUhbVoudg164r93CxDTrKRVWG",
      "Namespace": "dev",
      "Type": "kube"
    }
  }
}
Service deployment in Namespace Dev , ServiceDiscoveryProvider type is kube, you also can set pollkube ServiceDiscoveryProvider type.
  Note: Host、 Port and Token are no longer in use。

You use Ocelot to poll kubernetes for latest service information rather than per request. If you want to poll kubernetes for the latest services rather than per request (default behaviour) then you need to set the following configuration.

.. code-block:: json

  "ServiceDiscoveryProvider": {
   "Host": "192.168.0.13",
   "Port": 443,
   "Token": "txpc696iUhbVoudg164r93CxDTrKRVWG",
   "Namespace": "dev",
   "Type": "pollkube"
   "PollingInterval": 100
  } 

The polling interval is in milliseconds and tells Ocelot how often to call kubernetes for changes in service configuration.

Please note there are tradeoffs here. If you poll kubernetes it is possible Ocelot will not know if a service is down depending on your polling interval and you might get more errors than if you get the latest services per request. This really depends on how volatile your services are. I doubt it will matter for most people and polling may give a tiny performance improvement over calling kubernetes per request. 
There is no way for Ocelot to work these out for you.