HDFS-8696. Make the lower and higher watermark in the DN Netty server configurable. Contributed by Xiaobing Zhou.

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -652,6 +652,9 @@ Release 2.8.0 - UNRELEASED
     HDFS-9166. Move hftp / hsftp filesystem to hfds-client.
     (Mingliang Liu via wheat9)
 
+    HDFS-8696. Make the lower and higher watermark in the DN Netty server
+    configurable. (Xiaobing Zhou via wheat9)
+
   OPTIMIZATIONS
 
     HDFS-8026. Trace FSOutputSummer#writeChecksumChunks rather than

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java

@@ -63,6 +63,12 @@ public class DFSConfigKeys extends CommonConfigurationKeys {
       HdfsClientConfigKeys.DFS_HDFS_BLOCKS_METADATA_ENABLED_DEFAULT;
   public static final String DFS_WEBHDFS_ACL_PERMISSION_PATTERN_DEFAULT =
       HdfsClientConfigKeys.DFS_WEBHDFS_ACL_PERMISSION_PATTERN_DEFAULT;
+  public static final String  DFS_WEBHDFS_NETTY_LOW_WATERMARK =
+      "dfs.webhdfs.netty.low.watermark";
+  public static final int  DFS_WEBHDFS_NETTY_LOW_WATERMARK_DEFAULT = 32768;
+  public static final String  DFS_WEBHDFS_NETTY_HIGH_WATERMARK =
+      "dfs.webhdfs.netty.high.watermark";
+  public static final int  DFS_WEBHDFS_NETTY_HIGH_WATERMARK_DEFAULT = 65535;
 
   // HA related configuration
   public static final String  DFS_DATANODE_RESTART_REPLICA_EXPIRY_KEY = "dfs.datanode.restart.replica.expiration";

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/web/DatanodeHttpServer.java

@@ -21,6 +21,7 @@ import io.netty.bootstrap.ServerBootstrap;
 import io.netty.channel.ChannelFactory;
 import io.netty.channel.ChannelFuture;
 import io.netty.channel.ChannelInitializer;
+import io.netty.channel.ChannelOption;
 import io.netty.channel.ChannelPipeline;
 import io.netty.channel.EventLoopGroup;
 import io.netty.channel.nio.NioEventLoopGroup;
@@ -30,10 +31,12 @@ import io.netty.handler.codec.http.HttpRequestDecoder;
 import io.netty.handler.codec.http.HttpResponseEncoder;
 import io.netty.handler.ssl.SslHandler;
 import io.netty.handler.stream.ChunkedWriteHandler;
+
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.permission.FsPermission;
+import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.server.common.JspHelper;
 import org.apache.hadoop.hdfs.server.datanode.BlockScanner;
@@ -123,6 +126,18 @@ public class DatanodeHttpServer implements Closeable {
               conf, confForCreate));
         }
       });
+
+      this.httpServer.childOption(
+          ChannelOption.WRITE_BUFFER_HIGH_WATER_MARK,
+          conf.getInt(
+              DFSConfigKeys.DFS_WEBHDFS_NETTY_HIGH_WATERMARK,
+              DFSConfigKeys.DFS_WEBHDFS_NETTY_HIGH_WATERMARK_DEFAULT));
+      this.httpServer.childOption(
+          ChannelOption.WRITE_BUFFER_LOW_WATER_MARK,
+          conf.getInt(
+              DFSConfigKeys.DFS_WEBHDFS_NETTY_LOW_WATERMARK,
+              DFSConfigKeys.DFS_WEBHDFS_NETTY_LOW_WATERMARK_DEFAULT));
+
       if (externalHttpChannel == null) {
         httpServer.channel(NioServerSocketChannel.class);
       } else {