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Historical Queries on the IoT Broker

From version 5.3.3 the IoT Broker has an optional feature for saving NGSI data to a database and responding to historical queries on that data.

The following workflow explains how to enable and use this feature.

Enable historical queries

####As docker The docker container of the IoT Broker is already embedding a CouchDB server. Therefore just starting the docker container with the following parameter will enable the historical feature:

sudo docker run -t -p 8065:8065 -p 8060:8060  \
fiware/iotbroker:standalone-dev \
-p iotbroker_historicalagent="enabled"

NOTE: all the data stored in CouchDB will be canceled each time the docker will be stopped. In order to have permanent storage check the following (Permanent Storage in IoT Broker docker)

####As java application

For enabling historical queries, the IoT Broker needs to be connected to an instance of couchDB. This is achieved by the following steps.

  • The couchDB database needs to be installed either on the machine where the IoT Broker is running, or on a remote machine.

  • The Historical Agent feature of the IoT Broker must be enabled. For doing so add the following line into the IoTBroker-runner/iotbroker.conf.local:

iotbroker_historicalagent="enabled"

then run

cd IoTBroker-runner/
./setup.sh

and then restart the IoT Broker.

  • The above feature needs to be configured such that it knows the address and credentials of couchDB. In order to do so, add the following line in the file IoTBroker-runner/iotbroker.conf.local, and change them accordingly:
iotbroker_embeddedagent_couchdbname="historicalrepository"
iotbroker_embeddedagent_couchdbcreatedb=true
iotbroker_embeddedagent_couchdbprotocol="http"
iotbroker_embeddedagent_couchdbhost="127.0.0.1"
iotbroker_embeddedagent_couchdbport=5984
iotbroker_embeddedagent_historicallyTrackQueryResponseAndNotifications=false
iotbroker_embeddedagent_storeOnlyLatestValue=false
iotbroker_embeddedagent_localagentid="embeddedagent1"

Send some updates

Before history can be queried, it needs to exist. Therefore, the second step of the workflow is to send data to the IoT Broker in the form of updateContextRequest messages.

In this example, a time stamp is explicity specified in the form of NGSI metadata. While this makes the example reproducible, it is not necessary in real life to specify timestamps of updates - the IoT Broker will automatically add them whenever timestamps are not present.

The following examples assume that the IoT Broker is running on a machine with IP address 10.0.2.199 on port 8060.

HTTP POST to http://10.0.2.199:8060/ngsi10/updateContext
Content-Type:application/json
Accept:application/json

Body:
{
    "updateAction": "UPDATE",
    "contextElements": [{
        "entityId": {
            "id": "urn:x-iot:testbed1:sensor1",
            "isPattern": false
        },
        "attributes": [{
            "name": "temperature", 
            "type": "temperature ", 
            "contextValue": "26.00",
            "metadata": [{
                "name": "date",
                "type": "date",
                "value": "2015-08-18 16:54:36"
            }]
        }]
    }]
}

Reponse:

{"errorCode":null,"contextResponses":null}

Another update with a different timestamp

HTTP POST to http://10.0.2.199:8060/ngsi10/updateContext
Content-Type:application/json
Accept:application/json

Body:
{
    "updateAction": "UPDATE",
    "contextElements": [{
        "entityId": {
            "id": "urn:x-iot:testbed1:sensor1",
            "isPattern": false
        },
        "attributes": [{
            "name": "temperature", 
            "type": "temperature ", 
            "contextValue": "27.00",
            "metadata": [{
                "name": "date",
                "type": "date",
                "value": "2015-08-18 16:54:37"
            }]
        }]
    }]
}

Response:

{"errorCode":null,"contextResponses":null}

Another update with a different timestamp and different attribute

HTTP POST to http://10.0.2.199:8060/ngsi10/updateContext
Content-Type:application/json
Accept:application/json

Body:
{
    "updateAction": "UPDATE",
    "contextElements": [{
        "entityId": {
            "id": "urn:x-iot:testbed1:sensor2",
            "isPattern": false
        },
        "attributes": [{
            "name": "noise", 
            "type": "noise ", 
            "contextValue": "55.00",
            "metadata": [{
                "name": "date",
                "type": "date",
                "value": "2015-08-18 16:54:38"
            }]
        }]
    }]
}

Response:

{"errorCode":null,"contextResponses":null}

The final update does not contain an explicit timestamp:

HTTP POST to http://10.0.2.199:8060/ngsi10/updateContext
Content-Type:application/json
Accept:application/json

Body:
{
    "updateAction": "UPDATE",
    "contextElements": [{
        "entityId": {
            "id": "urn:x-iot:testbed1:sensor1",
            "isPattern": false
        },
        "attributes": [{
            "name": "temperature", 
            "type": "temperature ", 
            "contextValue": "28.00"
        }]
    }]
}

Response:

{"errorCode":null,"contextResponses":null}

Query the history

Now that the database is populated, the history can be queried using the queryContext operation.

The first query will ask for all entities with attributes temperature and noise; within the time interval 2015-08- 18T16:54:00+0000/2015-08-18T16:55:00+0000.

HTTP POST to http://10.0.2.199:8060/ngsi10/queryContext
Content-Type:application/json
Accept:application/json

Body:
{
    "entities": [{
        "id": ".*",
        "isPattern": true
    }],
    "attributes": ["temperature","noise"],
    "restriction": {
        "attributeExpression": "",
        "scopes": [{
            "scopeType": "ISO8601TimeInterval",
            "scopeValue": "2015-08-18T16:54:00+0000/2015-08-18T16:55:00+0000"
        }]
    }
}

Response:

{
    "contextResponses": [{
        "contextElement": {
            "entityId": {
                "id": "urn:x-iot:testbed1:sensor2",
                "type": null,
                "isPattern": false
            },
            "attributeDomainName": null,
            "domainMetadata": [],
            "attributes": [{
                "name": "noise",
                "type": "noise",
                "contextValue": "55.00",
                "metadata": [{
                    "name": "date",
                    "type": "date",
                    "value": "2015-08-18 16:54:38"
                }]
            }]
        },
        "statusCode": {
            "code": 200,
            "reasonPhrase": "OK",
            "details": "OK"
        }
    }, {
        "contextElement": {
            "entityId": {
                "id": "urn:x-iot:testbed1:sensor1",
                "type": null,
                "isPattern": false
            },
            "attributeDomainName": null,
            "domainMetadata": [],
            "attributes": [{
                "name": "temperature",
                "type": "temperature",
                "contextValue": "26.00",
                "metadata": [{
                    "name": "date",
                    "type": "date",
                    "value": "2015-08-18 16:54:36"
                }]
            }, {
                "name": "temperature",
                "type": "temperature",
                "contextValue": "27.00",
                "metadata": [{
                    "name": "date",
                    "type": "date",
                    "value": "2015-08-18 16:54:39"
                }]
            }]
        },
        "statusCode": {
            "code": 200,
            "reasonPhrase": "OK",
            "details": "OK"
        }
    }]
}

The second query asks for all entities with attributes temperature and noise, but this time without specifying a time interval. In this case the IoT Broker will respond with the list of the latest values matching the query.

HTTP POST to http://10.0.2.199:8060/ngsi10/queryContext
Content-Type:application/json
Accept:application/json

Body:
{
    "entities": [{
        "id": ".*",
        "isPattern": true
    }],
    "attributes": ["temperature","noise"]
}

Response:

{
    "contextResponses": [{
        "contextElement": {
            "entityId": {
                "id": "urn:x-iot:testbed1:sensor2",
                "type": null,
                "isPattern": false
            },
            "attributeDomainName": null,
            "domainMetadata": [],
            "attributes": [{
                "name": "noise",
                "type": "noise",
                "contextValue": "55.00",
                "metadata": [{
                    "name": "date",
                    "type": "date",
                    "value": "2015-08-18 16:54:38"
                }]
            }]
        },
        "statusCode": {
            "code": 200,
            "reasonPhrase": "OK",
            "details": "OK"
        }
    }, {
        "contextElement": {
            "entityId": {
                "id": "urn:x-iot:testbed1:sensor1",
                "type": null,
                "isPattern": false
            },
            "attributeDomainName": null,
            "domainMetadata": [],
            "attributes": [{
                "name": "temperature",
                "type": "temperature",
                "contextValue": "28.00",
                "metadata": [{
                    "name": "creation_time",
                    "type": "creation_time",
                    "value": "2016.01.25 13:50:39:002+01:00"
                }]
            }]
        },
        "statusCode": {
            "code": 200,
            "reasonPhrase": "OK",
            "details": "OK"
        }
    }]
}

Admitted metadata name and date format

The IoT Broker accepts different metadata name as timestamp metadata:

  • "date" with time format like "yyyy-MM-dd HH:mm:ss" like "2015-08-18 16:54:36"

  • "creation_time" with time format "yyyy.MM.dd HH:mm:ss:SSS Z" like "2017.09.13 10:38:14:838 +0100"

  • "nle:date" with time format "yyyy.MM.dd HH:mm:ss:SSS Z" like "2017.09.13 10:38:14:838 +0100"

  • "endtime" with time format "yyyy.MM.dd HH:mm:ss:SSS Z" like "2017.09.13 10:38:14:838 +0100". (this is meant for attributes that refer to a timewindow with a starttime and endtime of observation)