Fledge delta Filter

Fledge "delta" filter forwards deltas of reading data. A new reading is only sent onwards based on the configured processing mode and the data points that have changed in the new reading compared to last sent reading by the specified tolerance percentage/value.

By defining a minimum rate it is possible to force readings to be sent at that defined rate when there is no change in the value of the reading.

Rates may be defined as per second, per minute, per hour or per day.

Configuration items

The following configuration items are supported:

toleranceMeasure

Tells whether 'tolerance' is specified as a percentage or an absolute value.

tolerance

The percentage/absolute value of tolerance to use when comparing reading data. Only values that differ by more than this value will be considered as different from each other.

processingMode

Controls when the delta filter outputs a reading and what to include in this output reading. This is an enumeration with following options:

1. Include full reading if any Datapoint exceeds tolerance
2. Include full reading if all Datapoints exceed tolerance
3. Include only the Datapoints that exceed tolerance

minRate

The minimum rate at which readings should be sent. This is the rate at which readings will appear if there is no change in value.

rateUnit

The units in which minRate is defined (per second, minute, hour or day)

overrides

A JSON document that can be used to define specific tolerance values for an asset. This is defined as a set of name/value pairs for those assets that should use a tolerance percentage/value other than the global tolerance value specified above. 'toleranceMeasure' remains the same for all these entries as specified above.

Example

Send full reading if atleast one datapoint value differs by more than 1 percent from its value in the previously sent reading or at a rate of one reading every half hour if the change is less than this.

toleranceMeasure

percentage

tolerance

1

processingMode

Include full reading if any Datapoint exceeds tolerance

minRate

2

rateUnit

per hour

overrides

{ "temperature" : 15, "pressure" : 5 }

Build

To build Fledge "delta" C++ filter plugin:

$ mkdir build
$ cd build
$ cmake ..
$ make

• By default the Fledge develop package header files and libraries are expected to be located in /usr/include/fledge and /usr/lib/fledge
• If FLEDGE_ROOT env var is set and no -D options are set, the header files and libraries paths are pulled from the ones under the FLEDGE_ROOT directory. Please note that you must first run 'make' in the FLEDGE_ROOT directory.

You may also pass one or more of the following options to cmake to override this default behaviour:

• FLEDGE_SRC sets the path of a Fledge source tree
• FLEDGE_INCLUDE sets the path to Fledge header files
• FLEDGE_LIB sets the path to Fledge libraries
• FLEDGE_INSTALL sets the installation path of Random plugin

NOTE:

• The FLEDGE_INCLUDE option should point to a location where all the Fledge header files have been installed in a single directory.
• The FLEDGE_LIB option should point to a location where all the Fledge libraries have been installed in a single directory.
• 'make install' target is defined only when FLEDGE_INSTALL is set

Examples:

• no options

  $ cmake ..

• no options and FLEDGE_ROOT set

  $ export FLEDGE_ROOT=/some_fledge_setup

  $ cmake ..

• set FLEDGE_SRC

  $ cmake -DFLEDGE_SRC=/home/source/develop/Fledge ..

• set FLEDGE_INCLUDE

  $ cmake -DFLEDGE_INCLUDE=/dev-package/include ..

• set FLEDGE_LIB

  $ cmake -DFLEDGE_LIB=/home/dev/package/lib ..

• set FLEDGE_INSTALL

  $ cmake -DFLEDGE_INSTALL=/home/source/develop/Fledge ..

  $ cmake -DFLEDGE_INSTALL=/usr/local/fledge ..