HADOOP-15891. provide Regex Based Mount Point In Inode Tree

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/viewfs/ConfigUtil.java

@@ -166,6 +166,28 @@ public static void addLinkNfly(final Configuration conf, final String src,
     addLinkNfly(conf, getDefaultMountTableName(conf), src, null, targets);
   }
 
+  /**
+   * Add a LinkRegex to the config for the specified mount table.
+   * @param conf - get mountable config from this conf
+   * @param mountTableName - the mountable name of the regex config item
+   * @param srcRegex - the src path regex expression that applies to this config
+   * @param targetStr - the string of target path
+   * @param interceptorSettings - the serialized interceptor string to be
+   *                            applied while resolving the mapping
+   */
+  public static void addLinkRegex(
+      Configuration conf, final String mountTableName, final String srcRegex,
+      final String targetStr, final String interceptorSettings) {
+    String prefix = getConfigViewFsPrefix(mountTableName) + "."
+        + Constants.CONFIG_VIEWFS_LINK_REGEX + ".";
+    if ((interceptorSettings != null) && (!interceptorSettings.isEmpty())) {
+      prefix = prefix + interceptorSettings
+          + RegexMountPoint.SETTING_SRCREGEX_SEP;
+    }
+    String key = prefix + srcRegex;
+    conf.set(key, targetStr);
+  }
+
   /**
    * Add config variable for homedir for default mount table
    * @param conf - add to this conf

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/viewfs/Constants.java

@@ -86,6 +86,14 @@ public interface Constants {
    */
   String CONFIG_VIEWFS_LINK_MERGE_SLASH = "linkMergeSlash";
 
+  /**
+   * Config variable for specifying a regex link which uses regular expressions
+   * as source and target could use group captured in src.
+   * E.g. (^/(?<firstDir>\\w+), /prefix-${firstDir}) =>
+   *   (/path1/file1 => /prefix-path1/file1)
+   */
+  String CONFIG_VIEWFS_LINK_REGEX = "linkRegex";
+
   FsPermission PERMISSION_555 = new FsPermission((short) 0555);
 
   String CONFIG_VIEWFS_RENAME_STRATEGY = "fs.viewfs.rename.strategy";