HDFS-8101. DFSClient use of non-constant DFSConfigKeys pulls in WebHDFS classes at runtime. Contributed by Sean Busbey.

(cherry picked from commit 3fe61e0bb0d025a6acbb754027f73f3084b2f4d1)

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

@@ -167,6 +167,9 @@ Release 2.7.2 - 2016-01-25
 
     HDFS-9574. Reduce client failures during datanode restart (kihwal)
 
+    HDFS-8101. DFSClient use of non-constant DFSConfigKeys pulls in WebHDFS
+    classes at runtime. (Sean Busbey via atm)
+
   OPTIMIZATIONS
 
     HDFS-8722. Optimize datanode writes for small writes and flushes (kihwal)

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

@@ -24,7 +24,6 @@ import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.fs.CommonConfigurationKeys;
 import org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.RamDiskReplicaLruTracker;
-import org.apache.hadoop.hdfs.web.AuthFilter;
 import org.apache.hadoop.http.HttpConfig;
 
 /** 
@@ -234,7 +233,12 @@ public class DFSConfigKeys extends CommonConfigurationKeys {
   public static final String  DFS_NAMENODE_REPLICATION_STREAMS_HARD_LIMIT_KEY = "dfs.namenode.replication.max-streams-hard-limit";
   public static final int     DFS_NAMENODE_REPLICATION_STREAMS_HARD_LIMIT_DEFAULT = 4;
   public static final String  DFS_WEBHDFS_AUTHENTICATION_FILTER_KEY = "dfs.web.authentication.filter";
-  public static final String  DFS_WEBHDFS_AUTHENTICATION_FILTER_DEFAULT = AuthFilter.class.getName();
+  /* Phrased as below to avoid javac inlining as a constant, to match the behavior when
+     this was AuthFilter.class.getName(). Note that if you change the import for AuthFilter, you
+     need to update the literal here as well as TestDFSConfigKeys.
+   */
+  public static final String  DFS_WEBHDFS_AUTHENTICATION_FILTER_DEFAULT =
+      "org.apache.hadoop.hdfs.web.AuthFilter".toString();
   public static final String  DFS_WEBHDFS_ENABLED_KEY = "dfs.webhdfs.enabled";
   public static final boolean DFS_WEBHDFS_ENABLED_DEFAULT = true;
   public static final String  DFS_WEBHDFS_USER_PATTERN_KEY = "dfs.webhdfs.user.provider.user.pattern";

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestDFSConfigKeys.java

@@ -0,0 +1,37 @@
+/**
+ * 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.hadoop.hdfs;
+
+import org.apache.hadoop.hdfs.web.AuthFilter;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class TestDFSConfigKeys {
+
+  /**
+   * Make sure we keep the String literal up to date with what we'd get by calling
+   * class.getName.
+   */
+  @Test
+  public void testStringLiteralDefaultWebFilter() {
+    Assert.assertEquals("The default webhdfs auth filter should make the FQCN of AuthFilter.",
+        AuthFilter.class.getName(), DFSConfigKeys.DFS_WEBHDFS_AUTHENTICATION_FILTER_DEFAULT);
+  }
+ 
+}