def get_global_step(graph=None):
  """Get the global step tensor.

  The global step tensor must be an integer variable. We first try to find it
  in the collection `GLOBAL_STEP`, or by name `global_step:0`.

  Args:
    graph: The graph to find the global step in. If missing, use default graph.

  Returns:
    The global step variable, or `None` if none was found.

  Raises:
    TypeError: If the global step tensor has a non-integer type, or if it is not
      a `Variable`.
  """
  graph = ops.get_default_graph() if graph is None else graph
  global_step_tensor = None
  global_step_tensors = graph.get_collection(ops.GraphKeys.GLOBAL_STEP)
  if len(global_step_tensors) == 1:
    global_step_tensor = global_step_tensors[0]
  elif not global_step_tensors:
    try:
      global_step_tensor = graph.get_tensor_by_name('global_step:0')
    except KeyError:
      return None
  else:
    logging.error('Multiple tensors in global_step collection.')
    return None

  assert_global_step(global_step_tensor)
  return global_step_tensor

def main(unused_argv=None):
  if FLAGS.debug:
    logging.set_verbosity(logging.DEBUG)

  if not FLAGS.logdir:
    logging.error('A logdir must be specified. Run `tensorboard --help` for '
                  'details and examples.')
    return -1

  if FLAGS.debug:
    logging.info('Starting TensorBoard in directory %s', os.getcwd())

  path_to_run = ParseEventFilesFlag(FLAGS.logdir)
  multiplexer = event_multiplexer.AutoloadingMultiplexer(
      path_to_run=path_to_run, interval_secs=60,
      size_guidance=TENSORBOARD_SIZE_GUIDANCE)

  multiplexer.AutoUpdate(interval=30)

  factory = functools.partial(tensorboard_handler.TensorboardHandler,
                              multiplexer)
  try:
    server = ThreadedHTTPServer((FLAGS.host, FLAGS.port), factory)
  except socket.error:
    logging.error('Tried to connect to port %d, but that address is in use.',
                  FLAGS.port)
    return -2

  status_bar.SetupStatusBarInsideGoogle('TensorBoard', FLAGS.port)
  print('Starting TensorBoard on port %d' % FLAGS.port)
  print('(You can navigate to http://localhost:%d)' % FLAGS.port)
  server.serve_forever()

  def __exit__(self, exec_type, exec_value, exec_tb):
    if exec_type is errors.OpError:
      logging.error('Session closing due to OpError: %s', (exec_value,))

    for context_manager in reversed(self._context_managers):
      context_manager.__exit__(exec_type, exec_value, exec_tb)

    self.close()

def main(unused_argv=None):
  if FLAGS.debug:
    logging.set_verbosity(logging.DEBUG)
    logging.info('TensorBoard is in debug mode.')

  if not FLAGS.logdir:
    logging.error('A logdir must be specified. Run `tensorboard --help` for '
                  'details and examples.')
    return -1

  logging.info('Starting TensorBoard in directory %s', os.getcwd())

  path_to_run = ParseEventFilesFlag(FLAGS.logdir)
  logging.info('TensorBoard path_to_run is: %s', path_to_run)
  multiplexer = event_multiplexer.EventMultiplexer(
      size_guidance=TENSORBOARD_SIZE_GUIDANCE)
  # Ensure the Multiplexer initializes in a loaded state before it adds runs
  # So it can handle HTTP requests while runs are loading

  multiplexer.Reload()
  def _Load():
    start = time.time()
    for (path, name) in six.iteritems(path_to_run):
      multiplexer.AddRunsFromDirectory(path, name)
    multiplexer.Reload()
    duration = time.time() - start
    logging.info('Multiplexer done loading. Load took %0.1f secs', duration)
    t = threading.Timer(LOAD_INTERVAL, _Load)
    t.daemon = True
    t.start()
  t = threading.Timer(0, _Load)
  t.daemon = True
  t.start()

  factory = functools.partial(tensorboard_handler.TensorboardHandler,
                              multiplexer)
  try:
    server = ThreadedHTTPServer((FLAGS.host, FLAGS.port), factory)
  except socket.error:
    logging.error('Tried to connect to port %d, but that address is in use.',
                  FLAGS.port)
    return -2
  try:
    tag = resource_loader.load_resource('tensorboard/TAG').strip()
    logging.info('TensorBoard is tag: %s', tag)
  except IOError:
    logging.warning('Unable to read TensorBoard tag')
    tag = ''

  status_bar.SetupStatusBarInsideGoogle('TensorBoard %s' % tag, FLAGS.port)
  print('Starting TensorBoard %s on port %d' % (tag, FLAGS.port))
  print('(You can navigate to http://%s:%d)' % (FLAGS.host, FLAGS.port))
  server.serve_forever()

def _import_meta_graph_def(meta_graph_def):
  """Recreates a Graph saved in a a `MetaGraphDef` proto.

  This function adds all the nodes from the meta graph def proto to the current
  graph, recreates all the collections, and returns a saver from saver_def.

  Args:
    meta_graph_def: `MetaGraphDef` protocol buffer.

  Returns:
    A saver constructed rom `saver_def` in `meta_graph_def`.
  """
  # Gathers the list of nodes we are interested in.
  importer.import_graph_def(meta_graph_def.graph_def, name="")

  # Restores all the other collections.
  for key, col_def in meta_graph_def.collection_def.items():
    kind = col_def.WhichOneof("kind")
    if kind is None:
      logging.error("Cannot identify data type for collection %s. Skipping."
                    % key)
      continue
    from_proto = ops.get_from_proto_function(key)
    if from_proto:
      assert kind == "bytes_list"
      proto_type = ops.get_collection_proto_type(key)
      for value in col_def.bytes_list.value:
        proto = proto_type()
        proto.ParseFromString(value)
        ops.add_to_collection(key, from_proto(proto))
    else:
      field = getattr(col_def, kind)
      if kind == "node_list":
        for value in field.value:
          col_op = ops.get_default_graph().as_graph_element(value)
          ops.add_to_collection(key, col_op)
      elif kind == "int64_list":
        # NOTE(opensource): This force conversion is to work around the fact
        # that Python2 distinguishes between int and long, while Python3 has
        # only int.
        for value in field.value:
          ops.add_to_collection(key, int(value))
      else:
        for value in field.value:
          ops.add_to_collection(key, value)

  if meta_graph_def.HasField("saver_def"):
    return Saver(saver_def=meta_graph_def.saver_def)
  else:
    return Saver()

def CheckIsSupported():
  """Raises an OSError if the system isn't set up for Google Cloud Storage.

  Raises:
    OSError: If the system hasn't been set up so that TensorBoard can access
      Google Cloud Storage.   The error's message contains installation
      instructions.
  """
  try:
    subprocess.check_output(['gsutil', 'version'])
  except OSError as e:
    logging.error('Error while checking for gsutil: %s', e)
    raise OSError(
        'Unable to execute the gsutil binary, which is required for Google '
        'Cloud Storage support. You can find installation instructions at '
        'https://goo.gl/sST520')

  def _run(self, sess, enqueue_op, coord=None):
    """Execute the enqueue op in a loop, close the queue in case of error.

    Args:
      sess: A Session.
      enqueue_op: The Operation to run.
      coord: Optional Coordinator object for reporting errors and checking
        for stop conditions.
    """
    decremented = False
    try:
      while True:
        if coord and coord.should_stop():
          break
        try:
          sess.run(enqueue_op)
        except errors.OutOfRangeError:
          # This exception indicates that a queue was closed.
          with self._lock:
            self._runs -= 1
            decremented = True
            if self._runs == 0:
              try:
                sess.run(self._close_op)
              except Exception as e:
                # Intentionally ignore errors from close_op.
                logging.vlog(1, "Ignored exception: %s", str(e))
            return
    except Exception as e:
      # This catches all other exceptions.
      if coord:
        coord.request_stop(e)
      else:
        logging.error("Exception in QueueRunner: %s", str(e))
        with self._lock:
          self._exceptions_raised.append(e)
        raise
    finally:
      # Make sure we account for all terminations: normal or errors.
      if not decremented:
        with self._lock:
          self._runs -= 1

def main(unused_argv=None):
    if FLAGS.debug:
        logging.set_verbosity(logging.DEBUG)
        logging.info("TensorBoard is in debug mode.")

    if not FLAGS.logdir:
        logging.error("A logdir must be specified. Run `tensorboard --help` for " "details and examples.")
        return -1

    if FLAGS.debug:
        logging.info("Starting TensorBoard in directory %s", os.getcwd())

    path_to_run = ParseEventFilesFlag(FLAGS.logdir)
    multiplexer = event_multiplexer.AutoloadingMultiplexer(
        path_to_run=path_to_run, interval_secs=60, size_guidance=TENSORBOARD_SIZE_GUIDANCE
    )

    multiplexer.AutoUpdate(interval=30)

    factory = functools.partial(tensorboard_handler.TensorboardHandler, multiplexer)
    try:
        server = ThreadedHTTPServer((FLAGS.host, FLAGS.port), factory)
    except socket.error:
        logging.error("Tried to connect to port %d, but that address is in use.", FLAGS.port)
        return -2
    try:
        tag = resource_loader.load_resource("tensorboard/TAG").strip()
        logging.info("TensorBoard is tag: %s", tag)
    except IOError:
        logging.warning("Unable to read TensorBoard tag")
        tag = ""

    status_bar.SetupStatusBarInsideGoogle("TensorBoard %s" % tag, FLAGS.port)
    print("Starting TensorBoard %s on port %d" % (tag, FLAGS.port))
    print("(You can navigate to http://localhost:%d)" % FLAGS.port)
    server.serve_forever()

def main(unused_argv=None):
  if FLAGS.debug:
    logging.set_verbosity(logging.DEBUG)
    logging.info('TensorBoard is in debug mode.')

  if not FLAGS.logdir:
    msg = ('A logdir must be specified. Run `tensorboard --help` for '
           'details and examples.')
    logging.error(msg)
    print(msg)
    return -1

  logging.info('Starting TensorBoard in directory %s', os.getcwd())
  path_to_run = server.ParseEventFilesSpec(FLAGS.logdir)
  logging.info('TensorBoard path_to_run is: %s', path_to_run)

  multiplexer = event_multiplexer.EventMultiplexer(
      size_guidance=server.TENSORBOARD_SIZE_GUIDANCE,
      purge_orphaned_data=FLAGS.purge_orphaned_data)
  server.StartMultiplexerReloadingThread(multiplexer, path_to_run,
                                         FLAGS.reload_interval)
  try:
    tb_server = server.BuildServer(multiplexer, FLAGS.host, FLAGS.port)
  except socket.error:
    if FLAGS.port == 0:
      msg = 'Unable to find any open ports.'
      logging.error(msg)
      print(msg)
      return -2
    else:
      msg = 'Tried to connect to port %d, but address is in use.' % FLAGS.port
      logging.error(msg)
      print(msg)
      return -3

  try:
    tag = resource_loader.load_resource('tensorboard/TAG').strip()
    logging.info('TensorBoard is tag: %s', tag)
  except IOError:
    logging.warning('Unable to read TensorBoard tag')
    tag = ''

  status_bar.SetupStatusBarInsideGoogle('TensorBoard %s' % tag, FLAGS.port)
  print('Starting TensorBoard %s on port %d' % (tag, FLAGS.port))
  print('(You can navigate to http://%s:%d)' % (FLAGS.host, FLAGS.port))
  tb_server.serve_forever()