Trace plugin

The trace plugin is intended to generate a trace of what happens in PDI data store.

The plugin is very simple; just list its name in the specification tree and you're done.

data: #...
metadata: #...
plugins:
  trace:
  #...

The plugin then generates a (somewhat verbose) trace on the standard error.

For example:

[PDI][Test-plugin][00:00:00] *** info: Welcome!
[PDI][Test-plugin][00:00:00] *** info: =>>   data becoming available in the store: my_data
[PDI][Test-plugin][00:00:00] *** info: <<= data stop being available in the store: my_data
[PDI][Test-plugin][00:00:00] *** info: !!!                            named event: my_event
[PDI][Test-plugin][00:00:00] *** info: Goodbye!

Each line starting by =>> data becoming available in the store means a new piece of data has been shared.

Each line starting by <<= data stop being available in the store means a piece of data is being removed from the store.

Each line starting by !!! named event means a named event has been emitted.