streaming

class AckRequestSerializer extends TaskMessageSerializer[AckRequest]
class AckSerializer extends TaskMessageSerializer[Ack]
case class DAG(version: Int, processors: Map[ProcessorId, ProcessorDescription], graph: Graph[ProcessorId, PartitionerDescription]) extends Serializable with Product

DAG is wrapper for Graph for streaming applications.
type ExecutorId = Int
class InitialAckRequestSerializer extends TaskMessageSerializer[InitialAckRequest]
class LatencyProbeSerializer extends TaskMessageSerializer[LatencyProbe]
case class LifeTime(birth: TimeStamp, death: TimeStamp) extends Product with Serializable

Each processor has a LifeTime.
trait Processor[+T <: Task] extends ReferenceEqual

Processor is the blueprint for tasks.
case class ProcessorDescription(id: ProcessorId, taskClass: String, parallelism: Int, description: String = "", taskConf: UserConfig = null, life: LifeTime = LifeTime.Immortal, jar: AppJar = null) extends ReferenceEqual with Product with Serializable
type ProcessorId = Int
class StreamApplication extends Application

Represent a streaming application
class TaskIdSerializer extends TaskMessageSerializer[TaskId]
type TaskIndex = Int