HDFS-16471. Make HDFS ls tool cross platform (#4086)

* The source files for hdfs_ls
   uses getopt for parsing the
   command line arguments.
* getopt is available only on
   Linux and thus, isn't cross
   platform.
* Thus, we need to replace
   getopt with
   boost::program_options to
   make this tool cross platform.

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfspp/tests/tools/CMakeLists.txt

@@ -37,6 +37,7 @@ add_executable(hdfs_tool_tests
                 hdfs-rm-mock.cc
                 hdfs-get-mock.cc
                 hdfs-find-mock.cc
+                hdfs-ls-mock.cc
                 main.cc)
 target_include_directories(hdfs_tool_tests PRIVATE
                             ../tools
@@ -58,6 +59,7 @@ target_include_directories(hdfs_tool_tests PRIVATE
                             ../../tools/hdfs-rm
                             ../../tools/hdfs-get
                             ../../tools/hdfs-find
+                            ../../tools/hdfs-ls
                             ../../tools/hdfs-cat)
 target_link_libraries(hdfs_tool_tests PRIVATE
                        gmock_main
@@ -78,5 +80,6 @@ target_link_libraries(hdfs_tool_tests PRIVATE
                        hdfs_rm_lib
                        hdfs_get_lib
                        hdfs_find_lib
+                       hdfs_ls_lib
                        hdfs_cat_lib)
 add_test(hdfs_tool_tests hdfs_tool_tests)

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfspp/tests/tools/hdfs-ls-mock.cc

@@ -0,0 +1,67 @@
+/**
+ * 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.
+ */
+
+#include <functional>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
+#include "hdfs-ls-mock.h"
+#include "hdfs-tool-tests.h"
+
+namespace hdfs::tools::test {
+LsMock::~LsMock() = default;
+
+void LsMock::SetExpectations(std::function<std::unique_ptr<LsMock>()> test_case,
+                             const std::vector<std::string> &args) const {
+  // Get the pointer to the function that defines the test case
+  const auto test_case_func = test_case.target<std::unique_ptr<LsMock> (*)()>();
+  ASSERT_NE(test_case_func, nullptr);
+
+  // Set the expected method calls and their corresponding arguments for each
+  // test case
+  if (*test_case_func == &CallHelp<LsMock>) {
+    EXPECT_CALL(*this, HandleHelp()).Times(1).WillOnce(testing::Return(true));
+    return;
+  }
+
+  if (*test_case_func == &PassAPath<LsMock>) {
+    const auto arg1 = args[0];
+    EXPECT_CALL(*this, HandlePath(arg1, false))
+        .Times(1)
+        .WillOnce(testing::Return(true));
+  }
+
+  if (*test_case_func == &PassRecursivePath<LsMock>) {
+    const auto arg1 = args[0];
+    const auto arg2 = args[1];
+    ASSERT_EQ(arg1, "-R");
+    EXPECT_CALL(*this, HandlePath(arg2, true))
+        .Times(1)
+        .WillOnce(testing::Return(true));
+  }
+
+  if (*test_case_func == &PassRecursive<LsMock>) {
+    const auto arg1 = args[0];
+    ASSERT_EQ(arg1, "-R");
+  }
+}
+} // namespace hdfs::tools::test

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfspp/tests/tools/hdfs-ls-mock.h

@@ -0,0 +1,68 @@
+/**
+ * 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.
+ */
+
+#ifndef LIBHDFSPP_TOOLS_HDFS_LS_MOCK
+#define LIBHDFSPP_TOOLS_HDFS_LS_MOCK
+
+#include <functional>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include <gmock/gmock.h>
+
+#include "hdfs-ls.h"
+
+namespace hdfs::tools::test {
+/**
+ * {@class LsMock} is an {@class Ls} whereby it mocks the
+ * HandleHelp and HandlePath methods for testing their functionality.
+ */
+class LsMock : public hdfs::tools::Ls {
+public:
+  /**
+   * {@inheritdoc}
+   */
+  LsMock(const int argc, char **argv) : Ls(argc, argv) {}
+
+  // Abiding to the Rule of 5
+  LsMock(const LsMock &) = delete;
+  LsMock(LsMock &&) = delete;
+  LsMock &operator=(const LsMock &) = delete;
+  LsMock &operator=(LsMock &&) = delete;
+  ~LsMock() override;
+
+  /**
+   * Defines the methods and the corresponding arguments that are expected
+   * to be called on this instance of {@link HdfsTool} for the given test case.
+   *
+   * @param test_case An {@link std::function} object that points to the
+   * function defining the test case
+   * @param args The arguments that are passed to this test case
+   */
+  void SetExpectations(std::function<std::unique_ptr<LsMock>()> test_case,
+                       const std::vector<std::string> &args = {}) const;
+
+  MOCK_METHOD(bool, HandleHelp, (), (const, override));
+
+  MOCK_METHOD(bool, HandlePath, (const std::string &, const bool),
+              (const, override));
+};
+} // namespace hdfs::tools::test
+
+#endif

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfspp/tests/tools/hdfs-tool-tests.cc

@@ -33,6 +33,7 @@
 #include "hdfs-du-mock.h"
 #include "hdfs-find-mock.h"
 #include "hdfs-get-mock.h"
+#include "hdfs-ls-mock.h"
 #include "hdfs-mkdir-mock.h"
 #include "hdfs-move-to-local-mock.h"
 #include "hdfs-rename-snapshot-mock.h"
@@ -81,6 +82,12 @@ INSTANTIATE_TEST_SUITE_P(
                     CallHelp<hdfs::tools::test::DuMock>,
                     PassRecursivePath<hdfs::tools::test::DuMock>));
 
+INSTANTIATE_TEST_SUITE_P(
+    HdfsLs, HdfsToolBasicTest,
+    testing::Values(PassAPath<hdfs::tools::test::LsMock>,
+                    CallHelp<hdfs::tools::test::LsMock>,
+                    PassRecursivePath<hdfs::tools::test::LsMock>));
+
 INSTANTIATE_TEST_SUITE_P(
     HdfsDeleteSnapshot, HdfsToolBasicTest,
     testing::Values(CallHelp<hdfs::tools::test::DeleteSnapshotMock>,
@@ -180,6 +187,14 @@ INSTANTIATE_TEST_SUITE_P(
                     PassOwnerAndAPath<hdfs::tools::test::DuMock>,
                     PassPermissionsAndAPath<hdfs::tools::test::DuMock>));
 
+INSTANTIATE_TEST_SUITE_P(
+    HdfsLs, HdfsToolNegativeTestThrows,
+    testing::Values(Pass2Paths<hdfs::tools::test::LsMock>,
+                    Pass3Paths<hdfs::tools::test::LsMock>,
+                    PassNOptAndAPath<hdfs::tools::test::LsMock>,
+                    PassOwnerAndAPath<hdfs::tools::test::LsMock>,
+                    PassPermissionsAndAPath<hdfs::tools::test::LsMock>));
+
 INSTANTIATE_TEST_SUITE_P(
     HdfsCat, HdfsToolNegativeTestThrows,
     testing::Values(Pass2Paths<hdfs::tools::test::CatMock>));
@@ -262,6 +277,10 @@ INSTANTIATE_TEST_SUITE_P(
     HdfsDu, HdfsToolNegativeTestNoThrow,
     testing::Values(PassRecursive<hdfs::tools::test::DuMock>));
 
+INSTANTIATE_TEST_SUITE_P(
+    HdfsLs, HdfsToolNegativeTestNoThrow,
+    testing::Values(PassRecursive<hdfs::tools::test::LsMock>));
+
 INSTANTIATE_TEST_SUITE_P(
     HdfsChown, HdfsToolNegativeTestNoThrow,
     testing::Values(PassAPath<hdfs::tools::test::ChownMock>));

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfspp/tools/CMakeLists.txt

@@ -47,8 +47,7 @@ add_subdirectory(hdfs-mkdir)
 
 add_subdirectory(hdfs-rm)
 
-add_executable(hdfs_ls hdfs_ls.cc)
-target_link_libraries(hdfs_ls tools_common hdfspp_static)
+add_subdirectory(hdfs-ls)
 
 add_executable(hdfs_stat hdfs_stat.cc)
 target_link_libraries(hdfs_stat tools_common hdfspp_static)

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfspp/tools/hdfs-ls/CMakeLists.txt

@@ -0,0 +1,27 @@
+#
+# 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.
+#
+
+add_library(hdfs_ls_lib STATIC $<TARGET_OBJECTS:hdfs_tool_obj> hdfs-ls.cc)
+target_include_directories(hdfs_ls_lib PRIVATE ../../tools ${Boost_INCLUDE_DIRS})
+target_link_libraries(hdfs_ls_lib PRIVATE Boost::boost Boost::program_options tools_common hdfspp_static)
+
+add_executable(hdfs_ls main.cc)
+target_include_directories(hdfs_ls PRIVATE ../../tools)
+target_link_libraries(hdfs_ls PRIVATE hdfs_ls_lib)
+
+install(TARGETS hdfs_ls RUNTIME DESTINATION bin)

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfspp/tools/hdfs-ls/hdfs-ls.cc

@@ -0,0 +1,156 @@
+/**
+ * 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.
+ */
+
+#include <future>
+#include <iostream>
+#include <memory>
+#include <ostream>
+#include <sstream>
+#include <string>
+
+#include "hdfs-ls.h"
+#include "tools_common.h"
+
+namespace hdfs::tools {
+Ls::Ls(const int argc, char **argv) : HdfsTool(argc, argv) {}
+
+bool Ls::Initialize() {
+  auto add_options = opt_desc_.add_options();
+  add_options("help,h", "List information about the files");
+  add_options("recursive,R", "Operate on files and directories recursively");
+  add_options("path", po::value<std::string>(),
+              "The path for which we need to do ls");
+
+  // We allow only one positional argument to be passed to this tool. An
+  // exception is thrown if multiple arguments are passed.
+  pos_opt_desc_.add("path", 1);
+
+  po::store(po::command_line_parser(argc_, argv_)
+                .options(opt_desc_)
+                .positional(pos_opt_desc_)
+                .run(),
+            opt_val_);
+  po::notify(opt_val_);
+  return true;
+}
+
+std::string Ls::GetDescription() const {
+  std::stringstream desc;
+  desc << "Usage: hdfs_ls [OPTION] FILE" << std::endl
+       << std::endl
+       << "List information about the FILEs." << std::endl
+       << std::endl
+       << "  -R        list subdirectories recursively" << std::endl
+       << "  -h        display this help and exit" << std::endl
+       << std::endl
+       << "Examples:" << std::endl
+       << "hdfs_ls hdfs://localhost.localdomain:8020/dir" << std::endl
+       << "hdfs_ls -R /dir1/dir2" << std::endl;
+  return desc.str();
+}
+
+bool Ls::Do() {
+  if (!Initialize()) {
+    std::cerr << "Unable to initialize HDFS ls tool" << std::endl;
+    return false;
+  }
+
+  if (!ValidateConstraints()) {
+    std::cout << GetDescription();
+    return false;
+  }
+
+  if (opt_val_.count("help") > 0) {
+    return HandleHelp();
+  }
+
+  if (opt_val_.count("path") > 0) {
+    const auto path = opt_val_["path"].as<std::string>();
+    const auto recursive = opt_val_.count("recursive") > 0;
+    return HandlePath(path, recursive);
+  }
+
+  return false;
+}
+
+bool Ls::HandleHelp() const {
+  std::cout << GetDescription();
+  return true;
+}
+
+bool Ls::HandlePath(const std::string &path, const bool recursive) const {
+  // Building a URI object from the given path
+  auto uri = hdfs::parse_path_or_exit(path);
+
+  const auto fs = hdfs::doConnect(uri, true);
+  if (!fs) {
+    std::cerr << "Could not connect the file system. " << std::endl;
+    return false;
+  }
+
+  const auto promise = std::make_shared<std::promise<void>>();
+  auto future(promise->get_future());
+  auto result = hdfs::Status::OK();
+
+  /*
+   * Keep requesting more until we get the entire listing. Set the promise
+   * when we have the entire listing to stop.
+   *
+   * Find and GetListing guarantee that the handler will only be called once at
+   * a time, so we do not need any locking here. They also guarantee that the
+   * handler will be only called once with has_more_results set to false.
+   */
+  auto handler = [promise,
+                  &result](const hdfs::Status &status,
+                           const std::vector<hdfs::StatInfo> &stat_info,
+                           const bool has_more_results) -> bool {
+    // Print result chunks as they arrive
+    if (!stat_info.empty()) {
+      for (const auto &info : stat_info) {
+        std::cout << info.str() << std::endl;
+      }
+    }
+    if (!status.ok() && result.ok()) {
+      // We make sure we set the result only on the first error
+      result = status;
+    }
+    if (!has_more_results) {
+      promise->set_value(); // Set promise
+      return false;         // Request to stop sending results
+    }
+    return true; // Request more results
+  };
+
+  if (!recursive) {
+    // Asynchronous call to GetListing
+    fs->GetListing(uri.get_path(), handler);
+  } else {
+    // Asynchronous call to Find
+    fs->Find(uri.get_path(), "*", hdfs::FileSystem::GetDefaultFindMaxDepth(),
+             handler);
+  }
+
+  // Block until promise is set
+  future.get();
+  if (!result.ok()) {
+    std::cerr << "Error: " << result.ToString() << std::endl;
+    return false;
+  }
+  return true;
+}
+} // namespace hdfs::tools

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfspp/tools/hdfs-ls/hdfs-ls.h

@@ -0,0 +1,92 @@
+/**
+ * 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.
+ */
+
+#ifndef LIBHDFSPP_TOOLS_HDFS_LS
+#define LIBHDFSPP_TOOLS_HDFS_LS
+
+#include <string>
+
+#include <boost/program_options.hpp>
+
+#include "hdfs-tool.h"
+
+namespace hdfs::tools {
+/**
+ * {@class Ls} is an {@class HdfsTool} that lists information about the files.
+ */
+class Ls : public HdfsTool {
+public:
+  /**
+   * {@inheritdoc}
+   */
+  Ls(int argc, char **argv);
+
+  // Abiding to the Rule of 5
+  Ls(const Ls &) = default;
+  Ls(Ls &&) = default;
+  Ls &operator=(const Ls &) = delete;
+  Ls &operator=(Ls &&) = delete;
+  ~Ls() override = default;
+
+  /**
+   * {@inheritdoc}
+   */
+  [[nodiscard]] std::string GetDescription() const override;
+
+  /**
+   * {@inheritdoc}
+   */
+  [[nodiscard]] bool Do() override;
+
+protected:
+  /**
+   * {@inheritdoc}
+   */
+  [[nodiscard]] bool Initialize() override;
+
+  /**
+   * {@inheritdoc}
+   */
+  [[nodiscard]] bool ValidateConstraints() const override { return argc_ > 1; }
+
+  /**
+   * {@inheritdoc}
+   */
+  [[nodiscard]] bool HandleHelp() const override;
+
+  /**
+   * Handle the path argument that's passed to this tool.
+   *
+   * @param path The path to the directory for which we need to ls.
+   * @param recursive A boolean indicating whether ls needs to be
+   * performed recursively for the given path.
+   *
+   * @return A boolean indicating the result of this operation.
+   */
+  [[nodiscard]] virtual bool HandlePath(const std::string &path,
+                                        bool recursive) const;
+
+private:
+  /**
+   * A boost data-structure containing the description of positional arguments
+   * passed to the command-line.
+   */
+  po::positional_options_description pos_opt_desc_;
+};
+} // namespace hdfs::tools
+#endif

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfspp/tools/hdfs-ls/main.cc

@@ -0,0 +1,52 @@
+/**
+ * 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.
+ */
+
+#include <cstdlib>
+#include <exception>
+#include <iostream>
+
+#include <google/protobuf/stubs/common.h>
+
+#include "hdfs-ls.h"
+
+int main(int argc, char *argv[]) {
+  const auto result = std::atexit([]() -> void {
+    // Clean up static data on exit and prevent valgrind memory leaks
+    google::protobuf::ShutdownProtobufLibrary();
+  });
+  if (result != 0) {
+    std::cerr << "Error: Unable to schedule clean-up tasks for HDFS ls tool, "
+                 "exiting"
+              << std::endl;
+    std::exit(EXIT_FAILURE);
+  }
+
+  hdfs::tools::Ls ls(argc, argv);
+  auto success = false;
+
+  try {
+    success = ls.Do();
+  } catch (const std::exception &e) {
+    std::cerr << "Error: " << e.what() << std::endl;
+  }
+
+  if (!success) {
+    std::exit(EXIT_FAILURE);
+  }
+  return 0;
+}

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfspp/tools/hdfs_ls.cc

@@ -1,130 +0,0 @@
-/*
-  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.
-*/
-
-#include <google/protobuf/stubs/common.h>
-#include <unistd.h>
-#include <future>
-#include "tools_common.h"
-
-void usage(){
-  std::cout << "Usage: hdfs_ls [OPTION] FILE"
-      << std::endl
-      << std::endl << "List information about the FILEs."
-      << std::endl
-      << std::endl << "  -R        list subdirectories recursively"
-      << std::endl << "  -h        display this help and exit"
-      << std::endl
-      << std::endl << "Examples:"
-      << std::endl << "hdfs_ls hdfs://localhost.localdomain:8020/dir"
-      << std::endl << "hdfs_ls -R /dir1/dir2"
-      << std::endl;
-}
-
-int main(int argc, char *argv[]) {
-  //We should have at least 2 arguments
-  if (argc < 2) {
-    usage();
-    exit(EXIT_FAILURE);
-  }
-
-  bool recursive = false;
-  int input;
-
-  //Using GetOpt to read in the values
-  opterr = 0;
-  while ((input = getopt(argc, argv, "Rh")) != -1) {
-    switch (input)
-    {
-    case 'R':
-      recursive = true;
-      break;
-    case 'h':
-      usage();
-      exit(EXIT_SUCCESS);
-    case '?':
-      if (isprint(optopt))
-        std::cerr << "Unknown option `-" << (char) optopt << "'." << std::endl;
-      else
-        std::cerr << "Unknown option character `" << (char) optopt << "'." << std::endl;
-      usage();
-      exit(EXIT_FAILURE);
-    default:
-      exit(EXIT_FAILURE);
-    }
-  }
-  std::string uri_path = argv[optind];
-
-  //Building a URI object from the given uri_path
-  hdfs::URI uri = hdfs::parse_path_or_exit(uri_path);
-
-  std::shared_ptr<hdfs::FileSystem> fs = hdfs::doConnect(uri, true);
-  if (!fs) {
-    std::cerr << "Could not connect the file system. " << std::endl;
-    exit(EXIT_FAILURE);
-  }
-
-  std::shared_ptr<std::promise<void>> promise = std::make_shared<std::promise<void>>();
-  std::future<void> future(promise->get_future());
-  hdfs::Status status = hdfs::Status::OK();
-
-  /**
-    * Keep requesting more until we get the entire listing. Set the promise
-    * when we have the entire listing to stop.
-    *
-    * Find and GetListing guarantee that the handler will only be called once at a time,
-    * so we do not need any locking here. They also guarantee that the handler will be
-    * only called once with has_more_results set to false.
-    */
-  auto handler = [promise, &status]
-                  (const hdfs::Status &s, const std::vector<hdfs::StatInfo> & si, bool has_more_results) -> bool {
-    //Print result chunks as they arrive
-    if(!si.empty()) {
-      for (hdfs::StatInfo const& s : si) {
-        std::cout << s.str() << std::endl;
-      }
-    }
-    if(!s.ok() && status.ok()){
-      //We make sure we set 'status' only on the first error.
-      status = s;
-    }
-    if (!has_more_results) {
-      promise->set_value();  //set promise
-      return false;         //request stop sending results
-    }
-    return true;  //request more results
-  };
-
-  if(!recursive){
-    //Asynchronous call to GetListing
-    fs->GetListing(uri.get_path(), handler);
-  } else {
-    //Asynchronous call to Find
-    fs->Find(uri.get_path(), "*", hdfs::FileSystem::GetDefaultFindMaxDepth(), handler);
-  }
-
-  //block until promise is set
-  future.get();
-  if(!status.ok()) {
-    std::cerr << "Error: " << status.ToString() << std::endl;
-  }
-
-  // Clean up static data and prevent valgrind memory leaks
-  google::protobuf::ShutdownProtobufLibrary();
-  return 0;
-}