Configuring your driver for ArangoDB access
In this chapter you’ll learn how to configure a driver for accessing an ArangoDB deployment in Kubernetes.
The exact methods to configure a driver are specific to that driver.
Database endpoint(s)
The endpoint(s) (or URLs) to communicate with is the most important parameter your need to configure in your driver.
Finding the right endpoints depend on whether your client application is running in the same Kubernetes cluster as the ArangoDB deployment or not.
Client application in same Kubernetes cluster
If your client application is running in the same Kubernetes cluster as the ArangoDB deployment, you should configure your driver to use the following endpoint:
https://<deployment-name>.<namespace>.svc:8529
Only if your deployment has set spec.tls.caSecretName to None, should
you use http instead of https.
Client application outside Kubernetes cluster
If your client application is running outside the Kubernetes cluster in which the ArangoDB deployment is running, your driver endpoint depends on the external-access configuration of your ArangoDB deployment.
If the external-access of the ArangoDB deployment is of type LoadBalancer,
then use the IP address of that LoadBalancer like this:
https://<load-balancer-ip>:8529
If the external-access of the ArangoDB deployment is of type NodePort,
then use the IP address(es) of the Nodes of the Kubernetes cluster,
combined with the NodePort that is used by the external-access service.
For example:
https://<kubernetes-node-1-ip>:30123
You can find the type of external-access by inspecting the external-access Service.
To do so, run the following command:
kubectl get service -n <namespace-of-deployment> <deployment-name>-ea
The output looks like this:
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
example-simple-cluster-ea LoadBalancer 10.106.175.38 192.168.10.208 8529:31890/TCP 1s app=arangodb,arango_deployment=example-simple-cluster,role=coordinator
In this case the external-access is of type LoadBalancer with a load-balancer IP address
of 192.168.10.208.
This results in an endpoint of https://192.168.10.208:8529.
TLS settings
As mentioned before the ArangoDB deployment managed by the ArangoDB operator
will use a secure (TLS) connection unless you set spec.tls.caSecretName to None
in your ArangoDeployment.
When using a secure connection, you can choose to verify the server certificates provides by the ArangoDB servers or not.
If you want to verify these certificates, configure your driver with the CA certificate
found in a Kubernetes Secret found in the same namespace as the ArangoDeployment.
The name of this Secret is stored in the spec.tls.caSecretName setting of
the ArangoDeployment. If you don’t set this setting explicitly, it will be
set automatically.
Then fetch the CA secret using the following command (or use a Kubernetes client library to fetch it):
kubectl get secret -n <namespace> <secret-name> --template='{{index .data "ca.crt"}}' | base64 -D > ca.crt
This results in a file called ca.crt containing a PEM encoded, x509 CA certificate.
Query requests
For most client requests made by a driver, it does not matter if there is any kind of load-balancer between your client application and the ArangoDB deployment.
Note that even a simple Service of type ClusterIP already behaves as a
load-balancer.
The exception to this is cursor-related requests made to an ArangoDB Cluster
deployment. The Coordinator that handles an initial query request (that results
in a Cursor) will save some in-memory state in that Coordinator, if the result
of the query is too big to be transfer back in the response of the initial
request.
Follow-up requests have to be made to fetch the remaining data. These follow-up requests must be handled by the same Coordinator to which the initial request was made. As soon as there is a load-balancer between your client application and the ArangoDB cluster, it is uncertain which Coordinator will receive the follow-up request.
ArangoDB will transparently forward any mismatched requests to the correct Coordinator, so the requests can be answered correctly without any additional configuration. However, this incurs a small latency penalty due to the extra request across the internal network.
To prevent this uncertainty client-side, make sure to run your client application in the same Kubernetes cluster and synchronize your endpoints before making the initial query request. This will result in the use (by the driver) of internal DNS names of all Coordinators. A follow-up request can then be sent to exactly the same Coordinator.
If your client application is running outside the Kubernetes cluster the easiest way to work around it is by making sure that the query results are small enough to be returned by a single request. When that is not feasible, it is also possible to resolve this when the internal DNS names of your Kubernetes cluster are exposed to your client application and the resulting IP addresses are routable from your client application. To expose internal DNS names of your Kubernetes cluster, your can use CoreDNS.