Github user NicoK commented on a diff in the pull request:
https://github.com/apache/flink/pull/4509#discussion_r141283335
--- Diff: flink-runtime/src/main/java/org/apache/flink/runtime/io/network/netty/CreditBasedClientHandler.java ---
@@ -0,0 +1,283 @@
+/*
+ * 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.runtime.io.network.netty;
+
+import org.apache.flink.core.memory.MemorySegment;
+import org.apache.flink.core.memory.MemorySegmentFactory;
+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.netty.exception.LocalTransportException;
+import org.apache.flink.runtime.io.network.netty.exception.RemoteTransportException;
+import org.apache.flink.runtime.io.network.netty.exception.TransportException;
+import org.apache.flink.runtime.io.network.partition.PartitionNotFoundException;
+import org.apache.flink.runtime.io.network.partition.consumer.InputChannelID;
+import org.apache.flink.runtime.io.network.partition.consumer.RemoteInputChannel;
+
+import org.apache.flink.shaded.guava18.com.google.common.collect.Maps;
+import org.apache.flink.shaded.netty4.io.netty.channel.ChannelHandlerContext;
+import org.apache.flink.shaded.netty4.io.netty.channel.ChannelInboundHandlerAdapter;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.net.SocketAddress;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.atomic.AtomicReference;
+
+class CreditBasedClientHandler extends ChannelInboundHandlerAdapter {
+
+ private static final Logger LOG = LoggerFactory.getLogger(CreditBasedClientHandler.class);
+
+ private final ConcurrentMap<InputChannelID, RemoteInputChannel> inputChannels = new ConcurrentHashMap<>();
+
+ private final AtomicReference<Throwable> channelError = new AtomicReference<>();
+
+ /**
+ * Set of cancelled partition requests. A request is cancelled iff an input channel is cleared
+ * while data is still coming in for this channel.
+ */
+ private final ConcurrentMap<InputChannelID, InputChannelID> cancelled = Maps.newConcurrentMap();
--- End diff --
I guess, we can also use `ConcurrentHashMap` here and avoid the guava use
---