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Esper Service

This project provides a wrapper API for the CEP Engine Esper. To use this wrapper, run mvn install to generate a .war file, which can be deployed into the application server Tomcat8.

How to use the API is explained in detail in the following:

Data Sources
Event Management
Continuous Queries

Data Sources

A data source provides event for the Esper engine. By adding a data source, an input adapter is instantiated, which extracts data from this data source and forwards this data to the Esper engine. Currently, it is possible to add a MQTT-based Message Broker and a FIWARE Orion Context Broker as data sources, however, only if authentication is not configured.

Add data source:

POST /EsperService/datasources HTTP/1.1
Content-Type: application/json
Accept: application/json

{"protocol": "MQTT", "endpoint":"tcp://192.168.209.190:1883", "topics":["TempEvent"]}

HTTP/1.1 201 CREATED
Content-Type: application/json

{"datasource_id":"paho704154760161418","status":"BOUND"}

To add a Fiware Orion as data source, where EntityName = Demoraum and AttributeName = temp1:

POST /EsperService/datasources HTTP/1.1
Content-Type: application/json
Accept: application/json

{"protocol": "HTTP-Orion", "endpoint":"http://192.168.209.165:1026/v2/entities", "topics":["Demoraum/attrs/temp1/value"]}

HTTP/1.1 201 CREATED
Content-Type: application/json

{"datasource_id":"ha704154760161418","status":"BOUND"}

Get data sources:

GET /EsperService/datasources HTTP/1.1
Accept: application/json

HTTP/1.1 200 OK
Content-Type: application/json

[{"paho704154760161418":{"protocol":"MQTT","endpoint":"tcp://192.168.209.190:1883","topics":["TempEvent"]}}]

Get data source by {datasource_id}:

GET /EsperService/datasources/paho704154760161418 HTTP/1.1
Accept: application/json

HTTP/1.1 200 OK
Content-Type: application/json

{"protocol":"MQTT","endpoint":"tcp://192.168.209.190:1883","topics":["TempEvent"]}

Remove data source {datasource_id}:

DELETE /EsperService/datasources/paho704154760161418 HTTP/1.1

HTTP/1.1 200 OK
Content-Type: application/json

{"protocol":"MQTT","endpoint":"tcp://192.168.209.190:1883","topics":["TempEvent"]}

Event Management

The provided API allows the definition of new event types at runtime. Furthermore, besides providing events to Esper through a data source, it is also possible to send events to Esper through a HTTP request. In this case, no data source is necessary to be added.

Add event type:

POST /EsperService/event/types HTTP/1.1
Content-Type: application/json
Accept: application/json

{"eventtype": "create schema TempEvent(sensorID string, temperature double)"}

HTTP/1.1 200 OK
Content-Type: application/json

{"eventtype_id":"stmt_1","status":"running"}

Get event types:

GET /EsperService/event/types HTTP/1.1
Accept: application/json

HTTP/1.1 200 OK
Content-Type: application/json

[{"eventtype_id":"TempEvent","properties":{"temperature":"Double","sensorID":"String"}}]

Send event to the Esper engine:

POST /EsperService/event HTTP/1.1
Content-Type: application/json

{"TempEvent": {"sensorID": "A0", "temperature": 19.0}}

HTTP/1.1 204 No Content

Continuous Queries

The provided API allows the creation of continuous queries at runtime. Furthermore, subscribers can be added to a query in order to get notified when this query matches one or more input events. Currently, it is possible to add a MQTT-based Message Broker and a FIWARE Orion Context Broker as subscribers, however, only if authentication is not configured.

Create and start a continuous query:

POST /EsperService/queries HTTP/1.1
Content-Type: application/json

{"query": "select * from TempEvent(sensorID='A0')"}

HTTP/1.1 200 OK
Content-Type: application/json

{"query_id":"stmt_2","status":"running"}

Create and start a continuous query (with subscriber):

POST /EsperService/queries HTTP/1.1
Content-Type: application/json

{"query": "select * from TempEvent(sensorID='A0')", "subscriber": {"protocol": "MQTT", "endpoint":"tcp://192.168.209.190:1883", "topics":["situation"]}}

HTTP/1.1 200 OK
Content-Type: application/json

{"query_id":"stmt_3","status":"running"}

The subscriber to the topic situation will receive a message in the following format containing the triggered query_id and the event properties:

{"query_id":"stmt_3","event":{"temperature":39,"sensorID":"A0"}}

Get all continuous queries:

GET /EsperService/queries
Accept: application/json

HTTP/1.1 200 OK
Content-Type: application/json

[{"query_id":"stmt_2","status":"STARTED"},{"query_id":"stmt_1","status":"STARTED"},{"query_id":"stmt_3","status":"STARTED"}]

Stop continuous query {query_id}:

POST /EsperService/queries/stmt_2/stop

HTTP/1.1 200 OK
Content-Type: application/json

{"query_id":"stmt_2","status":"STOPPED"}

Start continuous query {query_id}:

POST /EsperService/queries/stmt_2/start

HTTP/1.1 200 OK
Content-Type: application/json

{"query_id":"stmt_2","status":"STARTED"}

Add subscriber to continuous query {query_id}:

POST /EsperService/queries/stmt_2/subscriptions
Content-Type: application/json

{"protocol": "MQTT", "endpoint":"tcp://192.168.209.190:1883", "topics":["situation"]}

HTTP/1.1 200 OK
Content-Type: application/json

{"subscription_id":"sub1520344781693","query_id":"stmt_2"}

The subscriber to the topic situation will receive a message in the following format containing the triggered query_id and the event properties:

{"query_id":"stmt_2","event":{"temperature":39,"sensorID":"A0"}}

To add Fiware Orion as subscriber, where EntityName = Demoraum-switch and AttributeName = cmd:

POST /EsperService/queries/stmt_2/subscriptions
Content-Type: application/json

{"protocol": "HTTP-Orion", "endpoint": "http://192.168.209.165:1026/v2/entities", "topics": ["Demoraum-switch/attrs/cmd/value"]}

HTTP/1.1 200 OK
Content-Type: application/json

{"subscription_id":"sub1520344781693","query_id":"stmt_2"}

Get subscribers of continuous query {query_id}:

GET /EsperService/queries/stmt_2/subscriptions
Accept: application/json

HTTP/1.1 200 OK
Content-Type: application/json

[{"sub1520344781693":{"protocol":"MQTT","endpoint":"tcp://192.168.209.190:1883","topics":["situation"]}}]

Remove subscriber {subscriber_id} of continuous query {query_id}:

DELETE /EsperService/queries/stmt_2/subscriptions/sub1520344781693
Accept: application/json

HTTP/1.1 200 OK
Content-Type: application/json

{"sub1520344781693":{"protocol":"MQTT","endpoint":"tcp://192.168.209.190:1883","topics":["situation"]}}

Delete continuous query {query_id}:

DELETE /EsperService/queries/stmt_2
Accept: application/json

HTTP/1.1 200 OK
Content-Type: application/json

{"query_id":"stmt_2","status":"DESTROYED"}

Haftungsausschluss

Dies ist ein Forschungsprototyp. Die Haftung für entgangenen Gewinn, Produktionsausfall, Betriebsunterbrechung, entgangene Nutzungen, Verlust von Daten und Informationen, Finanzierungsaufwendungen sowie sonstige Vermögens- und Folgeschäden ist, außer in Fällen von grober Fahrlässigkeit, Vorsatz und Personenschäden ausgeschlossen.

Disclaimer of Warranty

Unless required by applicable law or agreed to in writing, Licensor provides the Work (and each Contributor provides its Contributions) on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. You are solely responsible for determining the appropriateness of using or redistributing the Work and assume any risks associated with Your exercise of permissions under this License.