HDFS-15394. Add all available fs.viewfs.overload.scheme.target.<scheme>.impl classes in core-default.xml bydefault. Contributed by Uma Maheswara Rao G.

hadoop-common-project/hadoop-common/src/main/resources/core-default.xml

@@ -952,6 +952,116 @@
   </description>
 </property>
 
+<property>
+  <name>fs.viewfs.overload.scheme.target.hdfs.impl</name>
+  <value>org.apache.hadoop.hdfs.DistributedFileSystem</value>
+  <description>The DistributedFileSystem for view file system overload scheme
+   when child file system and ViewFSOverloadScheme's schemes are hdfs.
+   </description>
+</property>
+
+<property>
+  <name>fs.viewfs.overload.scheme.target.s3a.impl</name>
+  <value>org.apache.hadoop.fs.s3a.S3AFileSystem</value>
+  <description>The S3AFileSystem for view file system overload scheme when
+   child file system and ViewFSOverloadScheme's schemes are s3a.</description>
+</property>
+
+<property>
+  <name>fs.viewfs.overload.scheme.target.o3fs.impl</name>
+  <value>org.apache.hadoop.fs.ozone.OzoneFileSystem</value>
+  <description>The OzoneFileSystem for view file system overload scheme when
+   child file system and ViewFSOverloadScheme's schemes are o3fs.</description>
+</property>
+
+<property>
+  <name>fs.viewfs.overload.scheme.target.ftp.impl</name>
+  <value>org.apache.hadoop.fs.ftp.FTPFileSystem</value>
+  <description>The FTPFileSystem for view file system overload scheme when
+   child file system and ViewFSOverloadScheme's schemes are ftp.
+   </description>
+</property>
+
+<property>
+  <name>fs.viewfs.overload.scheme.target.webhdfs.impl</name>
+  <value>org.apache.hadoop.hdfs.web.WebHdfsFileSystem</value>
+  <description>The WebHdfsFileSystem for view file system overload scheme when
+   child file system and ViewFSOverloadScheme's schemes are webhdfs.
+  </description>
+</property>
+
+<property>
+  <name>fs.viewfs.overload.scheme.target.swebhdfs.impl</name>
+  <value>org.apache.hadoop.hdfs.web.SWebHdfsFileSystem</value>
+  <description>The SWebHdfsFileSystem for view file system overload scheme when
+   child file system and ViewFSOverloadScheme's schemes are swebhdfs.
+  </description>
+</property>
+
+<property>
+  <name>fs.viewfs.overload.scheme.target.file.impl</name>
+  <value>org.apache.hadoop.fs.LocalFileSystem</value>
+  <description>The LocalFileSystem for view file system overload scheme when
+   child file system and ViewFSOverloadScheme's schemes are file.
+  </description>
+</property>
+
+<property>
+  <name>fs.viewfs.overload.scheme.target.abfs.impl</name>
+  <value>org.apache.hadoop.fs.azurebfs.AzureBlobFileSystem</value>
+  <description>The AzureBlobFileSystem for view file system overload scheme
+   when child file system and ViewFSOverloadScheme's schemes are abfs.
+  </description>
+</property>
+
+<property>
+  <name>fs.viewfs.overload.scheme.target.abfss.impl</name>
+  <value>org.apache.hadoop.fs.azurebfs.SecureAzureBlobFileSystem</value>
+  <description>The SecureAzureBlobFileSystem for view file system overload
+   scheme when child file system and ViewFSOverloadScheme's schemes are abfss.
+  </description>
+</property>
+
+<property>
+  <name>fs.viewfs.overload.scheme.target.wasb.impl</name>
+  <value>org.apache.hadoop.fs.azure.NativeAzureFileSystem</value>
+  <description>The NativeAzureFileSystem for view file system overload scheme
+   when child file system and ViewFSOverloadScheme's schemes are wasb.
+  </description>
+</property>
+
+<property>
+  <name>fs.viewfs.overload.scheme.target.swift.impl</name>
+  <value>org.apache.hadoop.fs.swift.snative.SwiftNativeFileSystem</value>
+  <description>The SwiftNativeFileSystem for view file system overload scheme
+   when child file system and ViewFSOverloadScheme's schemes are swift.
+  </description>
+</property>
+
+<property>
+  <name>fs.viewfs.overload.scheme.target.oss.impl</name>
+  <value>org.apache.hadoop.fs.aliyun.oss.AliyunOSSFileSystem</value>
+  <description>The AliyunOSSFileSystem for view file system overload scheme
+   when child file system and ViewFSOverloadScheme's schemes are oss.
+  </description>
+</property>
+
+<property>
+  <name>fs.viewfs.overload.scheme.target.http.impl</name>
+  <value>org.apache.hadoop.fs.http.HttpFileSystem</value>
+  <description>The HttpFileSystem for view file system overload scheme
+   when child file system and ViewFSOverloadScheme's schemes are http.
+  </description>
+</property>
+
+<property>
+  <name>fs.viewfs.overload.scheme.target.https.impl</name>
+  <value>org.apache.hadoop.fs.http.HttpsFileSystem</value>
+  <description>The HttpsFileSystem for view file system overload scheme
+   when child file system and ViewFSOverloadScheme's schemes are https.
+  </description>
+</property>
+
 <property>
   <name>fs.AbstractFileSystem.ftp.impl</name>
   <value>org.apache.hadoop.fs.ftp.FtpFs</value>

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/conf/TestCommonConfigurationFields.java

@@ -124,6 +124,24 @@ public void initializeMemberVariables() {
     xmlPrefixToSkipCompare.add("fs.adl.");
     xmlPropsToSkipCompare.add("fs.AbstractFileSystem.adl.impl");
 
+    // ViewfsOverloadScheme target fs impl property keys are dynamically
+    // constructed and they are advanced props.
+    xmlPropsToSkipCompare.add("fs.viewfs.overload.scheme.target.abfs.impl");
+    xmlPropsToSkipCompare.add("fs.viewfs.overload.scheme.target.abfss.impl");
+    xmlPropsToSkipCompare.add("fs.viewfs.overload.scheme.target.file.impl");
+    xmlPropsToSkipCompare.add("fs.viewfs.overload.scheme.target.ftp.impl");
+    xmlPropsToSkipCompare.add("fs.viewfs.overload.scheme.target.hdfs.impl");
+    xmlPropsToSkipCompare.add("fs.viewfs.overload.scheme.target.http.impl");
+    xmlPropsToSkipCompare.add("fs.viewfs.overload.scheme.target.https.impl");
+    xmlPropsToSkipCompare.add("fs.viewfs.overload.scheme.target.o3fs.impl");
+    xmlPropsToSkipCompare.add("fs.viewfs.overload.scheme.target.oss.impl");
+    xmlPropsToSkipCompare.add("fs.viewfs.overload.scheme.target.s3a.impl");
+    xmlPropsToSkipCompare.
+        add("fs.viewfs.overload.scheme.target.swebhdfs.impl");
+    xmlPropsToSkipCompare.add("fs.viewfs.overload.scheme.target.webhdfs.impl");
+    xmlPropsToSkipCompare.add("fs.viewfs.overload.scheme.target.wasb.impl");
+    xmlPropsToSkipCompare.add("fs.viewfs.overload.scheme.target.swift.impl");
+
     // Azure properties are in a different class
     // - org.apache.hadoop.fs.azure.AzureNativeFileSystemStore
     // - org.apache.hadoop.fs.azure.SASKeyGeneratorImpl

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/fs/viewfs/TestViewFileSystemOverloadSchemeWithHdfsScheme.java

@@ -313,13 +313,17 @@ public void testCreateOnRootShouldFailEvenFallBackMountLinkConfigured()
    * Note: Above links created because to make fs initialization success.
    * Otherwise will not proceed if no mount links.
    *
-   * Don't set fs.viewfs.overload.scheme.target.hdfs.impl property.
+   * Unset fs.viewfs.overload.scheme.target.hdfs.impl property.
    * So, OverloadScheme target fs initialization will fail.
    */
   @Test(expected = UnsupportedFileSystemException.class, timeout = 30000)
   public void testInvalidOverloadSchemeTargetFS() throws Exception {
     final Path hdfsTargetPath = new Path(defaultFSURI + HDFS_USER_FOLDER);
+    String mountTableIfSet = conf.get(Constants.CONFIG_VIEWFS_MOUNTTABLE_PATH);
     conf = new Configuration();
+    if (mountTableIfSet != null) {
+      conf.set(Constants.CONFIG_VIEWFS_MOUNTTABLE_PATH, mountTableIfSet);
+    }
     addMountLinks(defaultFSURI.getAuthority(),
         new String[] {HDFS_USER_FOLDER, LOCAL_FOLDER,
             Constants.CONFIG_VIEWFS_LINK_FALLBACK },
@@ -331,6 +335,9 @@ public void testInvalidOverloadSchemeTargetFS() throws Exception {
         defaultFSURI.toString());
     conf.set(String.format(FS_IMPL_PATTERN_KEY, HDFS_SCHEME),
         ViewFileSystemOverloadScheme.class.getName());
+    conf.unset(String.format(
+        FsConstants.FS_VIEWFS_OVERLOAD_SCHEME_TARGET_FS_IMPL_PATTERN,
+        HDFS_SCHEME));
 
     try (FileSystem fs = FileSystem.get(conf)) {
       fs.createNewFile(new Path("/onRootWhenFallBack"));