Learning Apache Apex

The Apex operator model

Now that we have seen an example of a custom operator implementation, let's have a closer look at the Apex operator life cycle interfaces. The operators that are specified in the logical DAG will be deployed into the execution layer container (worker process) before they can do actual work. The Apex engine defines an execution life cycle for operators with corresponding interfaces and callback methods—the operator API. Operators that can be used in Apex applications have to be implemented in a way that conforms to the operator API. There are many prebuilt and ready to use operators in the Apex library, but the user isn't limited to those, as we have just seen (in the previous example) with the custom operator example. ...