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https://issues.apache.org/jira/browse/FLINK-8547?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16358128#comment-16358128
 ] 

ASF GitHub Bot commented on FLINK-8547:
---------------------------------------

Github user pnowojski commented on a diff in the pull request:

    https://github.com/apache/flink/pull/5400#discussion_r167163798
  
    --- Diff: 
flink-streaming-java/src/test/java/org/apache/flink/streaming/runtime/io/BarrierBufferTestBase.java
 ---
    @@ -0,0 +1,194 @@
    +/*
    + * 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.core.memory.MemorySegment;
    +import org.apache.flink.core.memory.MemorySegmentFactory;
    +import org.apache.flink.runtime.checkpoint.CheckpointMetaData;
    +import org.apache.flink.runtime.checkpoint.CheckpointMetrics;
    +import org.apache.flink.runtime.checkpoint.CheckpointOptions;
    +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.buffer.Buffer;
    +import org.apache.flink.runtime.io.network.buffer.FreeingBufferRecycler;
    +import org.apache.flink.runtime.io.network.buffer.NetworkBuffer;
    +import 
org.apache.flink.runtime.io.network.partition.consumer.BufferOrEvent;
    +import org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable;
    +import org.apache.flink.runtime.operators.testutils.DummyEnvironment;
    +
    +import org.hamcrest.BaseMatcher;
    +import org.hamcrest.Description;
    +
    +import java.util.Random;
    +
    +import static org.junit.Assert.assertEquals;
    +import static org.junit.Assert.assertNotNull;
    +import static org.junit.Assert.assertTrue;
    +
    +/**
    + * Utility class containing common methods for testing
    + * {@link BufferSpillerTest} and {@link CreditBasedBufferBlockerTest}.
    + */
    +public class BarrierBufferTestBase {
    +
    +   private static final Random RND = new Random();
    +
    +   private static int sizeCounter = 1;
    +
    +   public static BufferOrEvent createBarrier(long checkpointId, int 
channel) {
    +           return new BufferOrEvent(new CheckpointBarrier(
    +                   checkpointId, System.currentTimeMillis(), 
CheckpointOptions.forCheckpointWithDefaultLocation()), channel);
    +   }
    +
    +   public static BufferOrEvent createCancellationBarrier(long 
checkpointId, int channel) {
    --- End diff --
    
    Instead of using static methods please use inheritance - make 
`BarrierBufferTest` and `CreditBasedBarrierBufferTest` extend 
`BarrierBufferTestBase`. Especially that name `*Base` already suggests that.


> Implement CheckpointBarrierHandler not to spill data for exactly-once based 
> on credit-based flow control
> --------------------------------------------------------------------------------------------------------
>
>                 Key: FLINK-8547
>                 URL: https://issues.apache.org/jira/browse/FLINK-8547
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Network
>    Affects Versions: 1.5.0
>            Reporter: zhijiang
>            Assignee: zhijiang
>            Priority: Major
>
> Currently in exactly-once mode, the {{BarrierBuffer}} would block inputs with 
> barriers until all inputs have received the barrier for a given checkpoint. 
> To avoid back-pressuring the input streams which may cause distributed 
> deadlocks, the {{BarrierBuffer}} has to spill the data in disk files to 
> recycle the buffers for blocked channels.
>  
> Based on credit-based flow control, every channel has exclusive buffers, so 
> it is no need to spill data for avoiding deadlock. Then we implement a new 
> {{CheckpointBarrierHandler}} for only buffering the data for blocked channels 
> for better performance.
>  
> And this new {{CheckpointBarrierHandler}} can also be configured to use or 
> not in order to rollback the original mode for unexpected risks.



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