About /tmp/active Readiness Probes

In a TimesTen Classic active standby pair, the /tmp/active file is present in the container providing the active TimesTen database. In TimesTen Scaleout, the file is present on all instances with elements that are up and usable. In short, in TimesTen Classic and TimesTen Scaleout, the file is present in containers that have databases that can be used to run workloads.

Let's look at a use case for this type of readiness probe.

If you are using TimesTen client/server from applications within your Kubernetes cluster, you could list all the TimesTen Pods in your connection string, and the TimesTen Operator automatically routes client connections to ready instances. However, to avoid listing all TimesTen Pods in your connection string, you could create a Service that routes incoming client connections to ready instances. For this Service to work correctly, you need to use a /tmp/active readiness probe. This causes Kubernetes to only route incoming connections to appropriate TimesTen instances.

If you are using TimesTen client/server from applications outside your Kubernetes cluster, you must create such a Service. In this case, you must use a NodePort Service type. For this Service to work correctly, you need to use a /tmp/active readiness probe.

For information on a Kubernetes Service, see https://kubernetes.io/docs/concepts/services-networking/service/. For information on the NodePort Service type, see https://kubernetes.io/docs/concepts/services-networking/service/#type-nodeport.