Logging

Data Logging

A mechanism allowing agents to store timeseries data has been provided. In VOLTTRON 2.0 this facility was provided by an sMAP agent but it has now been folded into the new Historians. This service still uses the old format to maintain compatibility.

Data Logging Format

Data sent to the data logger should be sent as a JSON object that consists of a dictionary of dictionaries. The keys of the outer dictionary are used as the points to store the data items. The inner dictionary consists of 2 required fields and 1 optional. The required fields are "Readings" and "Units". Readings contains the data that will be written. It may contain either a single value, or a list of lists which consists of timestamp/value pairs. Units is a string that identifies the meaning of the scale values of the data. The optional entry is data_type, which indicates the type of the data to be stored. This may be either long or double.

{
    "test3": {
        "Readings": [[1377788595, 1.1],[1377788605,2.0]],
        "Units": "KwH",
        "data_type": "double"
    },
    "test4": {
        "Readings": [[1377788595, 1.1],[1377788605,2.0]],
        "Units": "TU",
        "data_type": "double"
    }
}

Example Code

        headers[headers_mod.FROM] = self._agent_id
        headers[headers_mod.CONTENT_TYPE] = headers_mod.CONTENT_TYPE.JSON
        
        mytime = int(time.time())
        
        content = {
            "listener": {
                "Readings": [[mytime, 1.0]],
                "Units": "TU",
                "data_type": "double"
            },
            "hearbeat": {
                "Readings": [[mytime, 1.0]],
                "Units": "TU",
                "data_type": "double"
            }
        }
        
        
        
        self.publish('datalogger/log/', headers, json.dumps(content))