Github user pnowojski commented on a diff in the pull request:
https://github.com/apache/flink/pull/5400#discussion_r165942614
--- Diff:
flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/io/CreditBasedBarrierBuffer.java
---
@@ -0,0 +1,529 @@
+/*
+ * 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.runtime.io;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.runtime.checkpoint.CheckpointMetaData;
+import org.apache.flink.runtime.checkpoint.CheckpointMetrics;
+import
org.apache.flink.runtime.checkpoint.decline.AlignmentLimitExceededException;
+import
org.apache.flink.runtime.checkpoint.decline.CheckpointDeclineException;
+import
org.apache.flink.runtime.checkpoint.decline.CheckpointDeclineOnCancellationBarrierException;
+import
org.apache.flink.runtime.checkpoint.decline.CheckpointDeclineSubsumedException;
+import
org.apache.flink.runtime.checkpoint.decline.InputEndOfStreamException;
+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.api.EndOfPartitionEvent;
+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
org.apache.flink.streaming.runtime.io.CreditBasedBufferBlocker.BufferOrEventSequence;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.ArrayDeque;
+
+import static org.apache.flink.util.Preconditions.checkArgument;
+
+/**
+ * The barrier buffer is {@link CheckpointBarrierHandler} that blocks
inputs with barriers until
+ * all inputs have received the barrier for a given checkpoint.
+ *
+ * <p>The BarrierBuffer continues receiving buffers from the blocked
channels and buffered them
+ * internally until the blocks are released. It will not cause deadlocks
based on credit-based
+ * flow control.
+ */
+@Internal
+public class CreditBasedBarrierBuffer implements CheckpointBarrierHandler {
+
+ private static final Logger LOG =
LoggerFactory.getLogger(CreditBasedBarrierBuffer.class);
+
+ /** The gate that the buffer draws its input from. */
+ private final InputGate inputGate;
+
+ /** Flags that indicate whether a channel is currently
blocked/buffered. */
+ private final boolean[] blockedChannels;
+
+ /** The total number of channels that this buffer handles data from. */
+ private final int totalNumberOfInputChannels;
+
+ /** The utility to buffer blocked data in the memory queue. */
+ private final CreditBasedBufferBlocker bufferBlocker;
+
+ /**
+ * The pending blocked buffer/event sequences. Must be consumed before
requesting further data
+ * from the input gate.
+ */
+ private final ArrayDeque<BufferOrEventSequence> queuedBuffered;
--- End diff --
Do we need this `queuedBuffered` and `currentBuffered` fields with
`CreditBasedBufferBlocker`? Why can not we just use `ArrayDeque<BufferOrEvent>
currentBuffers` field from `CreditBasedBufferBlocker` for this? Why do we need
this triple level buffering here? In original code it made sense, since instead
of `CreditBasedBufferBlocker` there was a `BufferSpiller`.
Getting rid of those three fields would vastly simplify this class.
---
