Flink源码分析-Graph

Flink以DAG的方式来执行程序，它会根据用户的代码生成三个Graph，但我认为实际上还有一个Graph，就是用户的程序直接映射出来的。

1. Plan ProgramGraph
2. StreamGraph
3. JobGraph
4. ExecutionGraph

JobGraph

public static boolean isChainable(StreamEdge edge, StreamGraph streamGraph) {
		StreamNode upStreamVertex = streamGraph.getSourceVertex(edge);
		StreamNode downStreamVertex = streamGraph.getTargetVertex(edge);

		StreamOperatorFactory<?> headOperator = upStreamVertex.getOperatorFactory();
		StreamOperatorFactory<?> outOperator = downStreamVertex.getOperatorFactory();

		return downStreamVertex.getInEdges().size() == 1
				&& outOperator != null
				&& headOperator != null
				&& upStreamVertex.isSameSlotSharingGroup(downStreamVertex)
				&& outOperator.getChainingStrategy() == ChainingStrategy.ALWAYS
				&& (headOperator.getChainingStrategy() == ChainingStrategy.HEAD ||
					headOperator.getChainingStrategy() == ChainingStrategy.ALWAYS)
				&& (edge.getPartitioner() instanceof ForwardPartitioner)
				&& edge.getShuffleMode() != ShuffleMode.BATCH
				&& upStreamVertex.getParallelism() == downStreamVertex.getParallelism()
				&& streamGraph.isChainingEnabled();
	}

判断两个算子是否能串联到一起

• 图允许链接
• 下游节点只有一个上游节点
• 有同样的槽共享组
• 上下游并行度一致
• 边的shuffle模式不能为batch
• 边的分区为Forward分区器
• 下游的链接策略为always
• 上游的链接策略为 HEAD 或者 always