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AMKO: Avi Multicluster Kubernetes Operator

Run AMKO

AMKO is a kubernetes operator used for multi-cluster application load balancing for Kubernetes workloads.

Alt text

AMKO is aware of the following object types:

  • Kubernetes

    • Ingress
    • Service type load balancer
  • Openshift

    • Routes
    • Service type load balancer

Dependencies

For Kubernetes clusters:

Components Version
Kubernetes 1.16+
AKO 1.4.3
AVI Controller 20.1.4-2p3+

For openshift clusters:

Components Version
Openshift 4.4+
AKO 1.4.3
AVI Controller 20.1.4-2p3+

Pre-requisites

To kick-start AMKO, we need:

  1. Atleast one kubernetes/openshift cluster.

  2. Atleast one AVI controller.

  3. AMKO assumes that it has connectivity to all the member clusters' kubernetes API servers. Without this, AMKO won't be able to watch over the kubernetes and openshift resources in the member clusters.

  4. Before deploying AMKO, one of the clusters have to be designated as the leader and rest of the clusters as followers. AMKO has to be deployed on all clusters (wherever federation is required). This is to ensure that the leader cluster's AMKO would federate the AMKO config objects like GSLBConfig and GlobalDeploymentPolicy objects to all follower clusters. See this for more details on the specifics of federation and how to recover from a disaster recovery scenario.

  5. On all clusters, create a namespace avi-system:

    $ kubectl create ns avi-system
    
  6. Create a kubeconfig file with the permissions to read the service and the ingress/route objects for all the member clusters. Follow this tutorial to create a kubeconfig file with multi-cluster access. Name this file gslb-members and generate a secret with the kubeconfig file in cluster-amko by following:

    $ kubectl create secret generic gslb-config-secret --from-file gslb-members -n avi-system
    

This has to be done for all the member clusters wherever AMKO is going to be deployed.

Note that the permissions provided in the kubeconfig file for all the clusters must have atleast the permissions to [get, list, watch] on:

  • Kubernetes ingress and service type load balancers.
  • Openshift routes and service type load balancers. AMKO also needs permissisons to [create, get, list, watch, update, delete] on:
  • GSLBConfig object
  • GlobalDeploymentPolicy object

Install using helm

Note that only helm v3 is supported.

Following steps have to be executed on all member clusters:

  1. Create the avi-system namespace:

    $ kubectl create ns avi-system
    
  2. Add this repository to your helm client:

    $ helm repo add amko https://projects.registry.vmware.com/chartrepo/ako
    
    

    Note: The helm charts are present in VMWare's public harbor repository

  3. Search the available charts for AMKO:

    $ helm search repo
    
    NAME     	CHART VERSION    	APP VERSION      	DESCRIPTION
    ako/amko	1.4.2	            1.4.2	            A helm chart for Avi Multicluster Kubernetes Operator
    
    
  4. Use the values.yaml from this repository to provide values related to Avi configuration. To get the values.yaml for a release, run the following command

    helm show values ako/amko --version 1.4.2 > values.yaml
    
    

    Values and their corresponding index can be found here

  5. To configure federation via values.yaml:

    • Set configs.federation.currentClusterIsLeader to true for the leader cluster. For all follower clusters, set this to false.
    • Set configs.federation.currentCluster to the current cluster context.
    • Add the member clusters to configs.federation.memberClusters.
  6. Install AMKO:

    $ helm install  ako/amko  --generate-name --version 1.4.2 -f /path/to/values.yaml  --set configs.gsllbLeaderController=<leader_controller_ip> --namespace=avi-system
    
  7. Check the installation:

    $ helm list -n avi-system
    
    NAME           	NAMESPACE 	REVISION	UPDATED                                	STATUS  	CHART                 	APP VERSION
    amko-1598451370	avi-system	1       	2020-08-26 14:16:21.889538175 +0000 UTC	deployed	amko-1.4.2	            1.4.2
    

Troubleshooting and Log collection

If you face any issues during installing/configuring/using AMKO, see if your problem is listed in the troubleshooting page.

Follow this to gather logs for tech-support in case of an unrecoverable failure.

Uninstall using helm

helm uninstall -n avi-system <amko-release-name>

If a user needs to remove the already created GSLB services, one has to remove the GDP object first. This will remove all the GSLB services selected via the GDP object.

kubectl delete gdp -n avi-system global-gdp

Also, delete the avi-system namespace:

kubectl delete ns avi-system

parameters

Parameter Description Default
configs.controllerVersion GSLB leader controller version 20.1.4
configs.federation.image.repository Image repository for AMKO federator projects.registry.vmware.com/ako/amko-federator
configs.federation.image.pullPolicy Image pull policy for AMKO federator IfNotPresent
configs.federation.currentCluster Current cluster context (required) Nil
configs.federation.currentClusterIsLeader Set to true if current cluster is the leader (required) false
configs.federation.memberClusters member clusters on which federation should be done
configs.gslbLeaderController GSLB leader site URL Nil
gslbLeaderCredentials.username GSLB leader controller username admin
gslbLeaderCredentials.password GSLB leader controller password
configs.memberClusters.clusterContext K8s member cluster context for GSLB cluster1-admin and cluster2-admin
configs.refreshInterval The time interval which triggers a AVI cache refresh 1800 seconds
configs.logLevel Log level to be used by AMKO to print the type of logs, supported values are INFO, DEBUG, WARN and ERROR INFO
configs.useCustomGlobalFqdn Select the GslbService FQDN mode for AMKO. If set to true, AMKO observes the HostRules to look for mapping between local and global FQDNs false
gdpConfig.appSelector.label{.key,.value} Selection criteria for applications, label key and value are provided Nil
gdpConfig.namespaceSelector.label{.key,.value} Selection criteria for namespaces, label key and value are provided Nil
gdpConfig.matchClusters List of clusters (names must match the names in configs.memberClusters) from where the objects will be selected Nil
gdpConfig.trafficSplit List of weights for clusters (names must match the names in configs.memberClusters), each weight must range from 1 to 20 Nil
gdpConfig.ttl Time To Live, ranges from 1-86400 seconds Nil
gdpConfig.healthMonitorRefs List of health monitor references to be applied on all Gslb Services Nil
gdpConfig.sitePersistenceRef Reference for a federated application persistence profile created on the Avi Controller Nil
gdpConfig.poolAlgorithmSettings Pool algorithm settings to be used by the GslbServices for traffic distribution across pool members. See pool algorithm settings to configure the appropriate settings. GSLB_ALGORITHM_ROUND_ROBIN

Custom resources

AMKO uses a custom resource to configure federation to member clusters:

AMKO uses the following custom resources to configure the GSLB services in the GSLB leader site:

  1. GSLBConfig
  2. GlobalDeploymentPolicy

Follow the above links to take a look at the CRD objects and how to use them.

If AMKO is installed via helm, it by default creates one instance of each type in the avi-system namespace. To see these objects:

$ kubectl get amkocluster amkocluster-federation -n avi-system
NAME                       AGE
amkocluster-federation     45m

$ kubectl get gc -n avi-system gc-1
NAME            AGE
gc-1            45m

$ kubectl get gdp -n avi-system
NAME         AGE
global-gdp   46m

Note that, only one instance of each GDP and GSLBConfig is supported and AMKO will ignore other instances.

  1. GSLBHostRule: Override specific GslbService properties. No instances are created by default (helm install). Users have to create these in the avi-system namespace. To see these objects:
$ kubectl get gslbhostrule -n avi-system

Editing runtime parameters of AMKO

The GDP object can be edited at runtime to change the application selection parameters, traffic split and the applicable clusters. AMKO will recognize these changes and will update the GSLBServices accordingly.

Changing only logLevel is permissible at runtime via an edit of the GSLBConfig. For all other changes to the GSLBConfig, the AMKO pod has to be restarted.

Choosing a mode of GslbService FQDN

There can be different requirements for a user to either use local FQDNs as the GslbService FQDNs, or use a different FQDN as the Global FQDN. Please see this to choose a mode fit for the use-case and enable accordingly.

Gslb Service Properties

Certain Gslb Service properties can be set and modified at runtime. If these are set through the GDP object, they are applied to all the Gslb Services. If a user wants to override specific properties, they can use a GSLBHostRule object for a GslbService.

Properties Configured via
TTL GDP, GSLBHostRule
Site Persistence GDP, GSLBHostRule
Custom Health Monitors GDP, GSLBHostRule
Third party members GSLBHostRule
Traffic Split GDP, GSLBHostRule
Pool Algorithm Settings GDP, GSLBHostRule

To set them, follow steps for GlobalDeploymentPolicy and for GSLBHostRule.