OrionSource

  • Import dependency.
import org.fiware.cosmos.orion.flink.connector.{OrionSource}
  • Add source to Flink Environment. Indicate what port you want to listen to (e.g. 9001).
val env = StreamExecutionEnvironment.getExecutionEnvironment
val eventStream = env.addSource(new OrionSource(9001))
  • Parse the received data.
val processedDataStream = eventStream.
    .flatMap(event => event.entities)
    // ...processing

The received data is a DataStream of objects of the class NgsiEvent. This class has the following attributes:

  • creationTime: Timestamp of arrival.

  • service: FIWARE service extracted from the HTTP headers.

  • servicePath: FIWARE service path extracted from the HTTP headers.

  • entities: Sequence of entites included in the message. Each entity has the following attributes:

    • id: Identifier of the entity.

    • type: Node type.

    • attrs: Map of attributes in which the key is the attribute name and the value is an object with the following properties:

      • type: Type of value (Float, Int,...).

      • value: Value of the attribute.

      • metadata: Additional metadata.

OrionSink

  • Import dependency.
import org.fiware.cosmos.orion.flink.connector.{OrionSink,OrionSinkObject,ContentType,HTTPMethod}
  • Add sink to source.
val processedDataStream = eventStream.
 // ... processing
 .map(obj =>
    new OrionSinkObject(
        "{\"temperature_avg\": { \"value\":"+obj.temperature+", \"type\": \"Float\"}}", // Stringified JSON message
        "http://context-broker-url:8080/v2/entities/Room1", // URL
        ContentType.JSON, // Content type
        HTTPMethod.POST) // HTTP method
 )

OrionSink.addSink( processedDataStream )

The sink accepts a DataStream of objects of the class OrionSinkObject. This class has 4 attributes:

  • content: Message content in String format. If it is a JSON, you need to make sure to stringify it before sending it.

  • url: URL to which the message should be sent.

  • contentType: Type of HTTP content of the message. It can be ContentType.JSON or ContentType.Plain.

  • method: HTTP method of the message. It can be HTTPMethod.POST, HTTPMethod.PUT or HTTPMethod.PATCH.

Production

When packaging your code in a JAR, it is common to exclude dependencies like Flink and Scala since they are typically provided by the execution environment. Nevertheless, it is necessary to include this connector in your packaged code, since it is not part of the Flink distribution.