GraphNode¶

GraphNode is an abstraction of graph nodes (for InternalStreamsBuilder to build a topology for StreamsBuilder).

Contract¶

writeToTopology¶

void writeToTopology(
  InternalTopologyBuilder topologyBuilder,
  Properties props)

Used when:

InternalStreamsBuilder is requested to build and optimize a topology

Implementations¶

BaseJoinProcessorNode
BaseRepartitionNode
ProcessorGraphNode
SourceGraphNode
StateStoreNode
StreamSinkNode
StreamTableJoinNode
StreamToTableNode
TableProcessorNode

Creating Instance¶

GraphNode takes the following to be created:

Node Name

Abstract Class

GraphNode is an abstract class and cannot be created directly. It is created indirectly for the concrete GraphNodes.

mergeNode¶

isMergeNode¶

boolean isMergeNode()

isMergeNode returns the mergeNode flag.

isMergeNode is used when:

InternalStreamsBuilder is requested to maybeAddNodeForOptimizationMetadata

setMergeNode¶

void setMergeNode(
  boolean mergeNode)

setMergeNode sets the mergeNode flag to the given mergeNode.

setMergeNode is used when:

KStreamImpl is requested to merge

Demo¶

import org.apache.kafka.streams.StreamsBuilder

// Without this class the following would not be available
// due to `protected` access level
class MyStreamsBuilder extends StreamsBuilder {
  val root = internalStreamsBuilder.root
}

val builder = new MyStreamsBuilder
builder.root

scala> println(builder.root)
StreamsGraphNode{nodeName='root', buildPriority=null, hasWrittenToTopology=false, keyChangingOperation=false, valueChangingOperation=false, mergeNode=false, parentNodes=[]}