Support for stacktrace logging of Java jobs

Current Situation

• Job developers who implement Java classes for jobs have to try/catch any job errors in order to write a stacktrace to the log output.
• See final posts of the linked SourceForge thread.

Desired Behavior

• It is desirable that a stacktrace is created and written to the log by the JobScheduler Master if required.
• This feature affects the spooler_log.error() method that could include an option to create a stacktrace.

Maintainer Notes

• A Java stacktrace can be enforced by use log categories, see log settings for example with the following setting in ./config/factory.ini

  log = java.* > ${SCHEDULER_DATA}/logs/scheduler.log
  

• We are reluctant to change the behavior of the spooler_log.error() method as changes to the logging mechanism tend to cause a number of implications. Instead we prefer to focus on the development of JobScheduler branch 2.x and will respect the requirement for a dynamic log setting to activate a stacktrace for individual exceptions.