[FLINK-16317][operators] Provide support for watermarks in MultipleInputStreamOperator

Author: pnowojski

flink-streaming-java/src/main/java/org/apache/flink/streaming/api/operators/AbstractInput.java

@@ -0,0 +1,48 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.streaming.api.operators;
+
+import org.apache.flink.annotation.Experimental;
+import org.apache.flink.streaming.api.watermark.Watermark;
+import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
+
+import static org.apache.flink.util.Preconditions.checkArgument;
+
+/**
+ * Base abstract implementation of {@link Input} interface intended to be used when extending
+ * {@link AbstractStreamOperatorV2}.
+ */
+@Experimental
+public abstract class AbstractInput<IN, OUT> implements Input<IN> {
+	protected final AbstractStreamOperatorV2<OUT> owner;
+	protected final int inputId;
+	protected final Output<StreamRecord<OUT>> output;
+
+	public AbstractInput(AbstractStreamOperatorV2<OUT> owner, int inputId) {
+		checkArgument(inputId > 0, "Inputs are index from 1");
+		this.owner = owner;
+		this.inputId = inputId;
+		this.output = owner.output;
+	}
+
+	@Override
+	public void processWatermark(Watermark mark) throws Exception {
+		owner.reportWatermark(mark, inputId);
+	}
+}

flink-streaming-java/src/main/java/org/apache/flink/streaming/api/operators/AbstractStreamOperatorV2.java

@@ -465,7 +465,7 @@ public void processWatermark(Watermark mark) throws Exception {
 	}
 
 	protected void reportWatermark(Watermark mark, int inputId) throws Exception {
-		inputWatermarks[inputId] = mark.getTimestamp();
+		inputWatermarks[inputId - 1] = mark.getTimestamp();
 		long newMin = mark.getTimestamp();
 		for (long inputWatermark : inputWatermarks) {
 			newMin = Math.min(inputWatermark, newMin);

flink-streaming-java/src/main/java/org/apache/flink/streaming/api/operators/Input.java

@@ -19,6 +19,7 @@
 package org.apache.flink.streaming.api.operators;
 
 import org.apache.flink.annotation.PublicEvolving;
+import org.apache.flink.streaming.api.watermark.Watermark;
 import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
 
 /**
@@ -31,4 +32,12 @@ public interface Input<IN> {
 	 * This method is guaranteed to not be called concurrently with other methods of the operator.
 	 */
 	void processElement(StreamRecord<IN> element) throws Exception;
+
+	/**
+	 * Processes a {@link Watermark} that arrived on the first input of this two-input operator.
+	 * This method is guaranteed to not be called concurrently with other methods of the operator.
+	 *
+	 * @see org.apache.flink.streaming.api.watermark.Watermark
+	 */
+	void processWatermark(Watermark mark) throws Exception;
 }

flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/io/StreamMultipleInputProcessor.java

@@ -81,13 +81,14 @@ public StreamMultipleInputProcessor(
 		this.inputSelectionHandler = checkNotNull(inputSelectionHandler);
 
 		List<Input> inputs = streamOperator.getInputs();
-		int operatorsCount = inputs.size();
+		int inputsCount = inputs.size();
 
-		this.inputProcessors = new InputProcessor[operatorsCount];
-		this.streamStatuses = new StreamStatus[operatorsCount];
+		this.inputProcessors = new InputProcessor[inputsCount];
+		this.streamStatuses = new StreamStatus[inputsCount];
 		this.numRecordsIn = numRecordsIn;
 
-		for (int i = 0; i < operatorsCount; i++) {
+		for (int i = 0; i < inputsCount; i++) {
+			streamStatuses[i] = StreamStatus.ACTIVE;
 			StreamTaskNetworkOutput dataOutput = new StreamTaskNetworkOutput<>(
 				inputs.get(i),
 				streamStatusMaintainer,
@@ -282,7 +283,8 @@ public void emitRecord(StreamRecord<T> record) throws Exception {
 
 		@Override
 		public void emitWatermark(Watermark watermark) throws Exception {
-			throw new UnsupportedOperationException();
+			inputWatermarkGauge.setCurrentWatermark(watermark.getTimestamp());
+			input.processWatermark(watermark);
 		}
 
 		@Override

flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/tasks/MultipleInputStreamTask.java

@@ -63,7 +63,7 @@ public void init() throws Exception {
 		for (int i = 0; i < inputDeserializers.length; i++) {
 			inputLists[i] = new ArrayList<>();
 			watermarkGauges[i] = new WatermarkGauge();
-			headOperator.getMetricGroup().gauge(MetricNames.currentInputWatermarkName(i), watermarkGauges[i]);
+			headOperator.getMetricGroup().gauge(MetricNames.currentInputWatermarkName(i + 1), watermarkGauges[i]);
 		}
 
 		MinWatermarkGauge minInputWatermarkGauge = new MinWatermarkGauge(watermarkGauges);