[FLINK-11877][runtime] Introduce new BarrierDiscarder class

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

@@ -0,0 +1,120 @@
+/*
+ * 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:https://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.runtime.io;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.runtime.io.network.api.CancelCheckpointMarker;
+import org.apache.flink.runtime.io.network.api.CheckpointBarrier;
+import org.apache.flink.runtime.io.network.partition.consumer.BufferOrEvent;
+import org.apache.flink.runtime.io.network.partition.consumer.InputGate;
+import org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable;
+
+import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
+
+/**
+ * The BarrierDiscarder discards checkpoint barriers have been received from which input channels.
+ */
+@Internal
+public class BarrierDiscarder implements CheckpointBarrierHandler {
+
+ // ------------------------------------------------------------------------
+
+ /** The input gate, to draw the buffers and events from. */
+ private final InputGate inputGate;
+
+ /**
+ * The number of channels. Once that many barriers have been received for a checkpoint, the
+ * checkpoint is considered complete.
+ */
+ private final int totalNumberOfInputChannels;
+
+
+ /** The listener to be notified on complete checkpoints. */
+ private AbstractInvokable toNotifyOnCheckpoint;
+
+ // ------------------------------------------------------------------------
+
+ public BarrierDiscarder(InputGate inputGate) {
+ this.inputGate = inputGate;
+ this.totalNumberOfInputChannels = inputGate.getNumberOfInputChannels();
+ }
+
+ @Override
+ public CompletableFuture<?> isAvailable() {
+ return inputGate.isAvailable();
+ }
+
+ @Override
+ public boolean isFinished() {
+ return inputGate.isFinished();
+ }
+
+ @Override
+ public Optional<BufferOrEvent> pollNext() throws Exception {
+ while (true) {
+ Optional<BufferOrEvent> next = inputGate.pollNext();
+ if (!next.isPresent()) {
+ // buffer or input exhausted
+ return next;
+ }
+
+ BufferOrEvent bufferOrEvent = next.get();
+ if (bufferOrEvent.isBuffer()) {
+ return next;
+ }
+ else if (bufferOrEvent.getEvent().getClass() != CheckpointBarrier.class &&
+ bufferOrEvent.getEvent().getClass() != CancelCheckpointMarker.class) {
+ // some other event
+ return next;
+ }
+ }
+ }
+
+ @Override
+ public void registerCheckpointEventHandler(AbstractInvokable toNotifyOnCheckpoint) {
+ if (this.toNotifyOnCheckpoint == null) {
+ this.toNotifyOnCheckpoint = toNotifyOnCheckpoint;
+ }
+ else {
+ throw new IllegalStateException("BarrierDiscarder already has a registered checkpoint notifyee");
+ }
+ }
+
+ @Override
+ public void cleanup() {
+
+ }
+
+ @Override
+ public boolean isEmpty() {
+ return true;
+ }
+
+ @Override
+ public long getAlignmentDurationNanos() {
+ // this one does not do alignment at all
+ return 0L;
+ }
+
+ @Override
+ public int getNumberOfInputChannels() {
+ return totalNumberOfInputChannels;
+ }
+}