Reading Custom Events (Recommendation)

You can modify the default DataSource to read

• Custom events other than the default rate and buy events.
• Events which involve different entity types other than the default user and item.

You can find the complete modified source code here.

Add the Custom Event

To read custom events, modify the function call PEventStore.find() in MyRecommendation/src/main/scala/DataSource.scala:

• Specify the names of events in eventNames parameters
• Specify the entity types involved in the events in the entityType and targetEntityType parameters accordingly

In this example below, we modify DataSource to read custom like and dislike events where a customer likes or dislikes a product. The event has new entityType customer and targetEntityType product:

val eventsRDD: RDD[Event] = PEventStore.find(
      appName = dsp.appName,
      entityType = Some("customer"), // MODIFIED
      eventNames = Some(List("like", "dislike")), // MODIFIED
      // targetEntityType is optional field of an event.
      targetEntityType = Some(Some("product")))(sc) // MODIFIED

Map the Custom Event

The ALS algorithm uses Rating object as input, so it is necessary to specify the mapping of your custom event to the Rating object. You can do so in MyRecommendation/src/main/scala/DataSource.scala.

To map like and dislike event to a Rating object with value of 4 and 1, respectively :

val ratingsRDD: RDD[Rating] = eventsRDD.map { event =>
      val rating = try {
        val ratingValue: Double = event.event match {
          // MODIFIED
          case "like" => 4.0 // map a like event to a rating of 4.0
          case "dislike" => 1.0  // map a like event to a rating of 1.0
          case _ => throw new Exception(s"Unexpected event ${event} is read.")
        }
        // entityId and targetEntityId is String
        Rating(event.entityId,
          event.targetEntityId.get,
          ratingValue)
      } catch {
        case e: Exception => {
          logger.error(s"Cannot convert ${event} to Rating. Exception: ${e}.")
          throw e
        }
      }
      rating
    }.cache()

That's it! Your engine can read custom like and dislike event.

Next: Customizing Data Preparator