Guillaume Boutry 822bfb0f50 Fix documentation typos

Change-Id: I6abc64755bff428543fdb22bd04ad217b1fa5ee9

2023-02-15 10:34:56 +01:00

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How-To expose a service outside of K8S

Overview

When Juju deploys an Operator Charm to Kubernetes by default a ClusterIP service entry is created for each application to provide resilient, load balanced access to the services it provides from within the Kubernetes deployment.

For the majority of OpenStack API services external ingress access is required to the API endpoints from outside of Kubernetes - this is used by both end-users of the cloud as well as from machine based charms supporting OpenStack Hypervisors.

Operator charms for API or other web services written using Sunbeam OpenStack will automatically patch the Juju created service entry to be of type LoadBalancer, enabling Kubernetes to expose the service to the outside world using a suitable Load Balancer implementation.

MicroK8S

For a MicroK8S deployment on bare metal MetalLB can be enabled to support this feature:

microk8s enable metallb

by default Microk8s will prompt for an IP address pool for MetalLB to use - this can also be provided in the enable command:

microk8s enable metallb:10.64.140.43-10.64.140.49

Please refer to the MicroK8S MetalLB add-on documentation for more details.

Charmed Kubernetes

For a Charmed Kubernetes deployment on bare metal MetalLB can also be used for creation of LoadBalancer access to services.

Operator Charms for MetalLB exist but don't yet support BGP mode for ECMP (Equal Cost Multi Path) based load balancing by integrating directly into the network infrastructure hosting the Kubernetes deployment.

For this reason its recommended to use the upstream manifests for deployment of MetalLB with a suitable ConfigMap for the BGP network configuration or Layer 2 configuration depending on the mode of operation desired:

kubectl apply -f https://raw.githubusercontent.com/metallb/metallb/v0.9.3/manifests/namespace.yaml
kubectl apply -f https://raw.githubusercontent.com/metallb/metallb/v0.9.3/manifests/metallb.yaml
# On first install only
kubectl create secret generic -n metallb-system memberlist --from-literal=secretkey="$(openssl rand -base64 128)"

Example ConfigMap for configuration of MetalLB in BGP mode:

apiVersion: v1
kind: ConfigMap
metadata:
  namespace: metallb-system
  name: config
data:
  config: |
    peers:
    - peer-address: 10.0.0.1
      peer-asn: 64512
      my-asn: 64512
    address-pools:
    - name: default
      protocol: bgp
      addresses:
      - 10.64.140.43-10.64.140.49

IP address pools and BGP peer configuration will be entirely deployment specific.

Service Access

Once MetalLB has created a LoadBalancer configuration for a service its external IP address will be populated in the service entry. Juju will automatically pick this address for use as the ingress address for the service on relations (which is not ideal for service communication within the Kubernetes deployment)

The IP address can also be discovered using the juju status command -the Load Balancer external IP will be detailed in the application information:

$ juju status cinder
Model    Controller  Cloud/Region       Version  SLA          Timestamp
sunbeam  maas-one    k8s-cloud/default  2.9.22   unsupported  11:21:51Z

App     Version  Status   Scale  Charm                    Store  Channel  Rev  OS          Address    Message
cinder           waiting      1  sunbeam-cinder-operator  local             0  kubernetes  10.0.0.40  installing agent

Unit       Workload  Agent  Address      Ports  Message
cinder/0*  unknown   idle   10.1.73.176

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