My first post on Oracle ESS briefly introduced the high level functional aspects of the framework. Here, I will discuss the ESS request execution processing stages - a key concept to understand when working with ESS.
The lifecycle of an ESS Job Execution begins when the client makes a request for the job submission and ends when the server responds with the execution state. The lifecycle consists of three main phases: PreProcess, Execute and PostProcess.
During the PreProcess phase, several actions can take place. For instance, setting request properties for work/output/log directories, verficiation of ESS request file directory, creating application session (a lightweight session object in the Fusion Apps context), database connection initialization, using requested NLS settings, and loading environment properties file for spawned execution are some of the purposes of PreProcessing. PreProcessor will run prior to every job request execution, and when a request is restarted after pausing.
Executable phase is where the actual job program runs. The program logic can be implemented in any of the supported ESS JobTypes i.e. Java, C, PL/SQL, Host, Perl, SQL, BIP etc. For example, Java job logic runs in the context of the J2ee ESS application hosting the job metadata. On the other hand, PL/SQL program logic written as procedures are executed as an Oracle RDBMS Scheduler job procedure (owned by ESS runtime schema) after the ESS wrapper procedure does some initialization/set up work. In general, for any job type the post-process handler is called only after the ESS mid-tier is notified the request executable has ended.
PostProcessing is performed only if the overall processing of the ESS request gets as far as the executable stage and it completes as success or warning, Post-processing is not done if the pre-processing or executable fails as error, or if the request is cancelled prior to post-processing. The main purpose of PostProcessor is to carry out general cleanup tasks and other actions to reflect the final state of the request before the job request can be deemed as fully complete. PostProcessing runs after the job has completed its execution to perform defined actions, such as Notification (using Oracle UMS) and storing the request log/output files to the Content Repository (i.e. Oracle UCM Server).
Finally, here are some important points to remember w.r.t the ESS request lifecycle:
- If the pre-process handler returns an error status, the business logic for that request will not be executed for that execution attempt. The request will normally transition to an ERROR state from which it may be retried if RETRIES are configured. It is important to note that pre-processor is not guaranteed to run in the same thread as the executable.
- If post-processing is attempted and returns as error, the overall request state is set to WARNING. Post Processing will only occur after the request has gone to a terminal state.
Please refer the Oracle ESS Developers Guide for more details and latest information.
