HADOOP-11918. Listing an empty s3a root directory throws FileNotFound. Contributed by Lei (Eddy) Xu.

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -1087,6 +1087,9 @@ Release 2.8.0 - UNRELEASED
     HADOOP-12252. LocalDirAllocator should not throw NPE with empty string
     configuration. (Zhihai Xu)
 
+    HADOOP-11918. Listing an empty s3a root directory throws FileNotFound.
+    (Lei (Eddy) Xu via cnauroth)
+
   OPTIMIZATIONS
 
     HADOOP-12051. ProtobufRpcEngine.invoke() should use Exception.toString()

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/contract/AbstractContractRootDirectoryTest.java

@@ -25,6 +25,7 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.io.IOException;
+import org.apache.hadoop.fs.FileStatus;
 
 import static org.apache.hadoop.fs.contract.ContractTestUtils.createFile;
 import static org.apache.hadoop.fs.contract.ContractTestUtils.dataset;
@@ -120,4 +121,17 @@ public abstract class AbstractContractRootDirectoryTest extends AbstractFSContra
     assertIsDirectory(root);
   }
 
+  @Test
+  public void testListEmptyRootDirectory() throws IOException {
+    //extra sanity checks here to avoid support calls about complete loss of data
+    skipIfUnsupported(TEST_ROOT_TESTS_ENABLED);
+    FileSystem fs = getFileSystem();
+    Path root = new Path("/");
+    FileStatus[] statuses = fs.listStatus(root);
+    for (FileStatus status : statuses) {
+      ContractTestUtils.assertDeleted(fs, status.getPath(), true);
+    }
+    assertEquals("listStatus on empty root-directory returned a non-empty list",
+        0, fs.listStatus(root).length);
+  }
 }

hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AFileSystem.java

@@ -983,6 +983,9 @@ public class S3AFileSystem extends FileSystem {
 
         return new S3AFileStatus(true, false,
             f.makeQualified(uri, workingDir));
+      } else if (key.isEmpty()) {
+        LOG.debug("Found root directory");
+        return new S3AFileStatus(true, true, f.makeQualified(uri, workingDir));
       }
     } catch (AmazonServiceException e) {
       if (e.getStatusCode() != 404) {