Field Detail

• DONE

  static final int DONE

  return status for performWork - only meaningful for enqueued client

  See Also:

  Constant Field Values

• REQUEUE

  static final int REQUEUE

  See Also:

  Constant Field Values

Method Detail

• performWork

  int performWork​(ContextManager context)
           throws StandardException

  Do whatever it is that you want the daemon to do for you. There may be multiple daemon objects on different thread calling performWork at the same time. The DaemonService will always call performWork with a context manager set up. the DaemonService will clean up the context if an exception is thrown. However, it is up to performWork to manage its own transaction. If you start a transaction in performWork, you must commit or abort it at the end. You may leave the transaction open so that other serviceable may use the transaction and context without starting a new one. On the same token, there may already be an opened transaction on the context. Serviceable performWork should always check the state of the context before use. A Serviceable object should be well behaved while it is performing the daemon work, i.e., it should not take too many resources or hog the CPU for too long or deadlock with anyone else.

  Parameters:

  context - the contextManager set up by the DaemonService. There may or may not be the necessary context on it, depending on which other Serviceable object it has done work for.

  Returns:

  the return status is only significant if the Serviceable client was enqueued instead of subscribed. For subscribed client, the return status is ignored. For enqueue client, it returns DONE or REQUEUE. If a REQUEUEd is returned, it would be desirable if this should not be serviceASAP, although no harm is done if this still maintains that this should be serviced ASAP ...

  Throws:

  StandardException - Standard Derby exception policy

  MT - depends on the work. Be wary of multiple DaemonService thread calling at the same time if you subscribe or enqueue multiple times.

• serviceASAP

  boolean serviceASAP()

  If this work should be done as soon as possible, then return true. If it doesn't make any difference if it is done sooner rather than later, then return false. The difference is whether or not the daemon service will be notified to work on this when this work is enqueued or subscribed, in case the serviceable work is put together but not sent to the daemon service directly, like in post commit processing

  MT - MT safe

• serviceImmediately

  boolean serviceImmediately()

  If this work should be done immediately on the user thread then return true. If it doesn't make any difference if this work is done on a the user thread immediately or if it is performed by another thread asynchronously later, then return false.