The idea behind this feature is to be able to insert a processing data function into the data flow from the north data ingress side to the south data egress side.
This feature should work in the same way as the filter plugins for readings.
What can be done ?
Modify a value in a set point.
Modify the parameters in an operation.
Modify the name of the set point or operation. Perform a simple textual substitution in order to change the name of a set point or operation.
Conditionally forward set point or operation. Only send control when a condition is satisfied.
Data conditioning. Remove set point or operation from the control stream if the values are suspect or outside of reasonable conditions.
Where Can it Be Done?
Filters can be applied in two locations in the Fledge system:
- In the north service as control is received in Fledge and before the control is send to the Dispatcher.
- In the south service as control is received from the Dispatcher and before it's send to the downstream system.
More than one filter can be added to a single south or north within a Fledge instance. Filters are placed in an ordered pipeline of filters that are applied to the data in the order of the pipeline. The output of the first filter becomes the input to the second. Filters can thus be combined to perform complex sets of operations on a particular data stream into Fledge or out of Fledge.
The same filter plugin can appear in multiple places within a filter pipeline, a different instance is created for each and each one has its own configuration.
How Can it Be Done?
Adding a control north or south filter should be done using Fledge GUI or Fledge REST API.