HDFS-15072. HDFS MiniCluster fails to start when run in directory path with a %. (#1775)

(cherry picked from commit a43c177f1d4c2b6149a2680dd23d91103eca3be0)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeImpl.java

@@ -196,9 +196,10 @@ public class FsVolumeImpl implements FsVolumeSpi {
         DFSConfigKeys.DFS_DATANODE_FSDATASETCACHE_MAX_THREADS_PER_VOLUME_KEY,
         DFSConfigKeys.DFS_DATANODE_FSDATASETCACHE_MAX_THREADS_PER_VOLUME_DEFAULT);
 
+    String escapedPath = parent.toString().replaceAll("%", "%%");
     ThreadFactory workerFactory = new ThreadFactoryBuilder()
         .setDaemon(true)
-        .setNameFormat("FsVolumeImplWorker-" + parent.toString() + "-%d")
+        .setNameFormat("FsVolumeImplWorker-" + escapedPath + "-%d")
         .build();
     ThreadPoolExecutor executor = new ThreadPoolExecutor(
         1, maxNumThreads,

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/TestFsDatasetImpl.java

@@ -951,4 +951,17 @@ public class TestFsDatasetImpl {
     }
   }
 
-}
+  @Test(timeout=30000)
+  public void testDataDirWithPercent() throws IOException {
+    String baseDir = new FileSystemTestHelper().getTestRootDir();
+    File dataDir = new File(baseDir, "invalidFormatString-%z");
+    dataDir.mkdirs();
+    FsVolumeImpl volumeFixed = new FsVolumeImplBuilder()
+        .setConf(new HdfsConfiguration())
+        .setDataset(dataset)
+        .setStorageID("storage-id")
+        .setStorageDirectory(
+            new StorageDirectory(StorageLocation.parse(dataDir.getPath())))
+        .build();
+  }
+}