Each task described in the process list file must be assigned a single Worker class.

In the following line from an example process list:

2|1|1|0|Download Delta File|process|DownloadFile||$ENV{APP_LOG_DIR}/download_delta_file.log

PyRunner will look within the ${APP_WORKER_DIR} (defined in the app_profile) for class DownloadFile in process.py.

The DownloadFile class is expected to extend the pyrunner.Worker abstract class and implement the run(self) method at minimum.

Worker Properties

Implementations of the Worker class have the following class properties available to them:

• self.argv - argument vector to access positional arguments optionally provided in the .lst file.
• self.logger - simple logger object with .info(<message>) and .error(<message>) methods that write provided string to the text file indicated in the .lst file ($ENV{APP_LOG_DIR} in the above example).
• self.context - a thread-safe key/value store shared across all tasks within a given instance of a job, which provides the ability to share data across separate tasks.

Worker Lifecycle Methods

Additionally, there exist lifecycle methods (in addition to the mandatory run(self) method) that may optionally be implemented:

• on_success(self) - only invoked upon successful execution of the run(self) method.
• on_fail(self) - only invoked upon failed execution of the run(self) method.
• on_exit(self) - always invoked upon completion of the run(self) method.

Return Codes and Exceptions

Return values are not explicitly required for any lifecycle method - the absence of an explicit return or prematurely returning None/0 will result in ending the task in success.

In the case that the task must be prematurely ended in failure, either a non-zero/not-None value may be returned:

  # Do something
  if my_value == 'something unexpected':
    self.logger.error('my_value is not assigned the appropriate value!')
    return 99

or an exception may be raised:

  # Do something
  if my_value == 'something unexpected':
    raise ValueError('my_value is not assigned the appropriate value!')

Raising an exception is the preferred method of ending a task in failure.

All exceptions, whether intentionally thrown or unexpectedly encountered, will have the exception message and stack trace written to the log file and return a non-zero return code.