In general, components should forward control messages

[gwilmer]

In general, components - specifically processor components - should forward control messages (current specification of the unit of work) through instead of dropping them on the floor.

The transformer component is a good example of this. Take this example:

1. File poller
2. File reader with unit of work = file
3. Transformer massaging some data
4. File writer

Today, if the file poller found 3 files and the file reader read each file, the file reader would send a control message specifying the end unit of work after each file. That unit of work would be used in the File Writer except that the Transformer today currently doesn't forward the control message on, so the result is the file writer never gets the unit of work boundary (the control message).

[nrichardson99]

The transformer now provides an option to Pass Along Control Messages