The getfilter, setfilter, and clearfilter utilities are used to manage telemetry filters associated with an instrument service's data stream.

The filters are decimation filters, which allow you to send every nth packet of the data stream. They may be applied separately to different types of packets (data, metadata, message, summary) or to all packets in the data stream.

Filters are used when a telemetry retriever such as portal or getPackets requests packets from an instrument service. The service decimates (sub-samples) the number of packets returned, returning only every nth packet.

The filters are expressed as a skip interval, i.e., the number of packets to skip. For example, a filter value of 3 would indicate that every 4th sample should be sent.

Note that the filters displayed by getfilter will be applied by the service sequentially. E.g. in the above below, "filter 0" passes all packets of all types, but "filter 1" will subsequently remove all sensor data and message packets.

Filter Utilities

There are a number of utilities for using telemetry filters:

• getfilter
• setfilter
• clearfilter

The following table describes the utilities and their use. The options are described in greater detail in a separate table below.

Options

Example output:

					
					% clearfilter surface 1101
					% setfilter -types data message -skip -1 1101
					
					A subsequent invocation of getfilter shows:
					
					% getfilter localhost 1101
					SIAM version $Name:  $
					filter 0: types: SensorData Metadata DeviceMessage Summary : skip 0
					filter 1: types: SensorData DeviceMessage : skip -1
					
					Note that the filters displayed by getfilter will be applied by the service sequentially. 
					E.g. in the above example, "filter 0" passes all packets of all types, but "filter 1" will 
					subsequently remove all sensor data and message packets.