netty-codec: Manage read-flow explicitly in MessageAggregator

codec/src/main/java/io/netty/handler/codec/MessageAggregator.java

@@ -399,6 +399,17 @@ public abstract class MessageAggregator<I, S, C extends ByteBufHolder, O extends
                 new TooLongFrameException("content length exceeded " + maxContentLength() + " bytes."));
     }
 
+    @Override
+    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
+        // We might need keep reading the channel until the full message is aggregated.
+        //
+        // See https://github.com/netty/netty/issues/6583
+        if (currentMessage != null && !ctx.channel().config().isAutoRead()) {
+            ctx.read();
+        }
+        ctx.fireChannelReadComplete();
+    }
+
     @Override
     public void channelInactive(ChannelHandlerContext ctx) throws Exception {
         try {

codec/src/test/java/io/netty/handler/codec/MessageAggregatorTest.java

@@ -0,0 +1,94 @@
+/*
+ * Copyright 2017 The Netty Project
+ *
+ * The Netty Project 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 io.netty.handler.codec;
+
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+import static org.mockito.Mockito.*;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufHolder;
+import io.netty.buffer.DefaultByteBufHolder;
+import io.netty.buffer.Unpooled;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.ChannelOutboundHandlerAdapter;
+import io.netty.channel.embedded.EmbeddedChannel;
+import io.netty.util.CharsetUtil;
+
+public class MessageAggregatorTest {
+    private static final class ReadCounter extends ChannelOutboundHandlerAdapter {
+        int value;
+
+        @Override
+        public void read(ChannelHandlerContext ctx) throws Exception {
+            value++;
+            ctx.read();
+        }
+    }
+
+    abstract static class MockMessageAggregator
+        extends MessageAggregator<ByteBufHolder, ByteBufHolder, ByteBufHolder, ByteBufHolder> {
+
+        protected MockMessageAggregator() {
+            super(1024);
+        }
+
+        @Override
+        protected ByteBufHolder beginAggregation(ByteBufHolder start, ByteBuf content) throws Exception {
+            return start.replace(content);
+        }
+    }
+
+    private static ByteBufHolder message(String string) {
+        return new DefaultByteBufHolder(
+            Unpooled.copiedBuffer(string, CharsetUtil.US_ASCII));
+    }
+
+    @SuppressWarnings("unchecked")
+    @Test
+    public void testReadFlowManagement() throws Exception {
+        ReadCounter counter = new ReadCounter();
+        ByteBufHolder first = message("first");
+        ByteBufHolder chunk = message("chunk");
+        ByteBufHolder last = message("last");
+
+        MockMessageAggregator agg = spy(MockMessageAggregator.class);
+        when(agg.isStartMessage(first)).thenReturn(true);
+        when(agg.isContentMessage(chunk)).thenReturn(true);
+        when(agg.isContentMessage(last)).thenReturn(true);
+        when(agg.isLastContentMessage(last)).thenReturn(true);
+
+        EmbeddedChannel embedded = new EmbeddedChannel(counter, agg);
+        embedded.config().setAutoRead(false);
+
+        assertFalse(embedded.writeInbound(first));
+        assertFalse(embedded.writeInbound(chunk));
+        assertTrue(embedded.writeInbound(last));
+
+        assertEquals(3, counter.value); // 2 reads issued from MockMessageAggregator
+                                        // 1 read issued from EmbeddedChannel constructor
+
+        ByteBufHolder all = new DefaultByteBufHolder(Unpooled.wrappedBuffer(
+            first.content().retain(), chunk.content().retain(), last.content().retain()));
+        ByteBufHolder out = embedded.readInbound();
+
+        assertEquals(all, out);
+        assertTrue(all.release() && out.release());
+        assertFalse(embedded.finish());
+    }
+}