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ServicesAndLoadBalancer.md

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Services and load balancer

The ArangoDB Kubernetes Operator will create services that can be used to reach the ArangoDB servers from inside the Kubernetes cluster.

By default, the ArangoDB Kubernetes Operator will also create an additional service to reach the ArangoDB deployment from outside the Kubernetes cluster.

For exposing the ArangoDB deployment to the outside, there are 2 options:

  • Using a NodePort service. This will expose the deployment on a specific port (above 30.000) on all nodes of the Kubernetes cluster.
  • Using a LoadBalancer service. This will expose the deployment on a load-balancer that is provisioned by the Kubernetes cluster.

The LoadBalancer option is the most convenient, but not all Kubernetes clusters are able to provision a load-balancer. Therefore we offer a third (and default) option: Auto. In this option, the ArangoDB Kubernetes Operator tries to create a LoadBalancer service. It then waits for up to a minute for the Kubernetes cluster to provision a load-balancer for it. If that has not happened after a minute, the service is replaced by a service of type NodePort.

To inspect the created service, run:

kubectl get services <deployment-name>-ea

To use the ArangoDB servers from outside the Kubernetes cluster you have to add another service as explained below.

Services

If you do not want the ArangoDB Kubernetes Operator to create an external-access service for you, set spec.externalAccess.Type to None.

If you want to create external access services manually, follow the instructions below.

Single server

For a single server deployment, the operator creates a single Service named <cluster-name>. This service has a normal cluster IP address.

Full cluster

For a full cluster deployment, the operator creates two Services.

  • <cluster-name>_servers a headless Service intended to provide DNS names for all pods created by the operator. It selects all ArangoDB & ArangoSync servers in the cluster.

  • <cluster-name> a normal Service that selects only the coordinators of the cluster. This Service is configured with ClientIP session affinity. This is needed for cursor requests, since they are bound to a specific coordinator.

When the coordinators are asked to provide endpoints of the cluster (e.g. when calling client.SynchronizeEndpoints() in the go driver) the DNS names of the individual Pods will be returned (<pod>.<cluster-name>_servers.<namespace>.svc)

Full cluster with DC2DC

For a full cluster with datacenter replication deployment, the same Services are created as for a Full cluster, with the following additions:

  • <cluster-name>_sync a normal Service that selects only the syncmasters of the cluster.

Load balancer

To reach the ArangoDB servers from outside the Kubernetes cluster, you have to deploy additional services.

You can use LoadBalancer or NodePort services, depending on your Kubernetes deployment.

This service should select:

  • arangodb_cluster_name: <cluster-name>
  • role: coordinator

For example:

kind: Service
apiVersion: v1
metadata:
  name: arangodb-cluster-exposed
spec:
  selector:
    arangodb_cluster_name: arangodb-cluster
    role: coordinator
  type: NodePort
  ports:
  - protocol: TCP
    port: 8529
    targetPort: 8529
    nodePort: 30529