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https://issues.apache.org/jira/browse/FLINK-8547?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16352279#comment-16352279
]
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_r165933824
--- 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
--- End diff --
Please explain a little bit more `It will not cause deadlocks based on
credit-based flow control` part in the comment.
> 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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