# pylint: disable=g-bad-file-header # Copyright 2016 The TensorFlow Authors. All Rights Reserved. # # Licensed 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. # ============================================================================== """A wrapper of Session API which runs hooks.""" import abc import os import sys import six from tensorflow.core.protobuf import config_pb2 from tensorflow.python.checkpoint import checkpoint as trackable_util from tensorflow.python.checkpoint import graph_view from tensorflow.python.distribute import distribute_coordinator_context from tensorflow.python.framework import errors from tensorflow.python.framework import ops from tensorflow.python.ops import array_ops from tensorflow.python.ops import control_flow_ops from tensorflow.python.ops import lookup_ops from tensorflow.python.ops import resources from tensorflow.python.ops import variables from tensorflow.python.platform import tf_logging as logging from tensorflow.python.summary import summary from tensorflow.python.training import basic_session_run_hooks from tensorflow.python.training import coordinator from tensorflow.python.training import queue_runner from tensorflow.python.training import saver as training_saver from tensorflow.python.training import session_manager as sm from tensorflow.python.training import session_run_hook from tensorflow.python.util import function_utils from tensorflow.python.util.tf_export import tf_export # The list of exceptions that we should recover from. Exceptions not in this # list may terminate the job. _PREEMPTION_ERRORS = (errors.AbortedError, errors.UnavailableError) # Value that indicates no value was provided. USE_DEFAULT = object() @tf_export(v1=['train.Scaffold']) class Scaffold(object): """Structure to create or gather pieces commonly needed to train a model. When you build a model for training you usually need ops to initialize variables, a `Saver` to checkpoint them, an op to collect summaries for the visualizer, and so on. Various libraries built on top of the core TensorFlow library take care of creating some or all of these pieces and storing them in well known collections in the graph. The `Scaffold` class helps pick these pieces from the graph collections, creating and adding them to the collections if needed. If you call the scaffold constructor without any arguments, it will pick pieces from the collections, creating default ones if needed when `scaffold.finalize()` is called. You can pass arguments to the constructor to provide your own pieces. Pieces that you pass to the constructor are not added to the graph collections. The following pieces are directly accessible as attributes of the `Scaffold` object: * `saver`: A `tf.compat.v1.train.Saver` object taking care of saving the variables. Picked from and stored into the `SAVERS` collection in the graph by default. * `init_op`: An op to run to initialize the variables. Picked from and stored into the `INIT_OP` collection in the graph by default. * `ready_op`: An op to verify that the variables are initialized. Picked from and stored into the `READY_OP` collection in the graph by default. * `ready_for_local_init_op`: An op to verify that global state has been initialized and it is alright to run `local_init_op`. Picked from and stored into the `READY_FOR_LOCAL_INIT_OP` collection in the graph by default. This is needed when the initialization of local variables depends on the values of global variables. * `local_init_op`: An op to initialize the local variables. Picked from and stored into the `LOCAL_INIT_OP` collection in the graph by default. * `summary_op`: An op to run and merge the summaries in the graph. Picked from and stored into the `SUMMARY_OP` collection in the graph by default. You can also pass the following additional pieces to the constructor: * `init_feed_dict`: A session feed dictionary that should be used when running the init op. * `init_fn`: A callable to run after the init op to perform additional initializations. The callable will be called as `init_fn(scaffold, session)`. """ def __init__(self, init_op=None, init_feed_dict=None, init_fn=None, ready_op=None, ready_for_local_init_op=None, local_init_op=None, summary_op=None, saver=None, copy_from_scaffold=None, local_init_feed_dict=None): """Create a scaffold. Args: init_op: Optional op for initializing variables. init_feed_dict: Optional session feed dictionary to use when running the init_op. init_fn: Optional function to use to initialize the model after running the init_op. Will be called as `init_fn(scaffold, session)`. ready_op: Optional op to verify that the variables are initialized. Must return an empty 1D string tensor when the variables are initialized, or a non-empty 1D string tensor listing the names of the non-initialized variables. ready_for_local_init_op: Optional op to verify that the global variables are initialized and `local_init_op` can be run. Must return an empty 1D string tensor when the global variables are initialized, or a non-empty 1D string tensor listing the names of the non-initialized global variables. local_init_op: Optional op to initialize local variables. summary_op: Optional op to gather all summaries. Must return a scalar string tensor containing a serialized `Summary` proto. saver: Optional `tf.compat.v1.train.Saver` object to use to save and restore variables. May also be a `tf.train.Checkpoint` object, in which case object-based checkpoints are saved. This will also load some object-based checkpoints saved from elsewhere, but that loading may be fragile since it uses fixed keys rather than performing a full graph-based match. For example if a variable has two paths from the `Checkpoint` object because two `Model` objects share the `Layer` object that owns it, removing one `Model` may change the keys and break checkpoint loading through this API, whereas a graph-based match would match the variable through the other `Model`. copy_from_scaffold: Optional scaffold object to copy fields from. Its fields will be overwritten by the provided fields in this function. local_init_feed_dict: Optional session feed dictionary to use when running the local_init_op. """ if copy_from_scaffold is not None: if not isinstance(copy_from_scaffold, Scaffold): raise TypeError('copy_from_scaffold is not a Scaffold instance.') # We need _coalesce since Tensor is not converted to bool automatically, # so the common idiom of (a or b) does not work. coalesce = lambda a, b: a if a is not None else b init_op = coalesce(init_op, copy_from_scaffold.init_op) init_feed_dict = coalesce(init_feed_dict, copy_from_scaffold.init_feed_dict) # Use the original init_fn provided by the user to init the new Scaffold. init_fn = coalesce(init_fn, copy_from_scaffold._user_init_fn) # pylint: disable=protected-access ready_op = coalesce(ready_op, copy_from_scaffold.ready_op) ready_for_local_init_op = coalesce( ready_for_local_init_op, copy_from_scaffold.ready_for_local_init_op) local_init_op = coalesce(local_init_op, copy_from_scaffold.local_init_op) local_init_feed_dict = coalesce(local_init_feed_dict, copy_from_scaffold.local_init_feed_dict) summary_op = coalesce(summary_op, copy_from_scaffold.summary_op) saver = coalesce(saver, copy_from_scaffold.saver) # NOTE(touts): modifying the init function to be passed the scaffold is a # hack to make it easy to find the saver. Is there a better way? self._user_init_fn = init_fn if init_fn: self._init_fn = lambda sess: init_fn(self, sess) else: self._init_fn = None self._init_op = init_op self._init_feed_dict = init_feed_dict self._ready_op = ready_op self._ready_for_local_init_op = ready_for_local_init_op self._local_init_op = local_init_op self._local_init_feed_dict = local_init_feed_dict self._summary_op = summary_op self._saver = saver def finalize(self): """Creates operations if needed and finalizes the graph.""" if self._init_op is None: def default_init_op(): return control_flow_ops.group( variables.global_variables_initializer(), resources.initialize_resources(resources.shared_resources()), ops.get_collection('saved_model_initializers')) self._init_op = Scaffold.get_or_default('init_op', ops.GraphKeys.INIT_OP, default_init_op) if self._ready_op is None: def default_ready_op(): return array_ops.concat([ variables.report_uninitialized_variables(), resources.report_uninitialized_resources() ], 0) self._ready_op = Scaffold.get_or_default('ready_op', ops.GraphKeys.READY_OP, default_ready_op) if self._ready_for_local_init_op is None: def default_ready_for_local_init_op(): return array_ops.concat([ variables.report_uninitialized_variables( variables.global_variables()), resources.report_uninitialized_resources( resources.shared_resources()) ], 0) self._ready_for_local_init_op = Scaffold.get_or_default( 'ready_for_local_init_op', ops.GraphKeys.READY_FOR_LOCAL_INIT_OP, default_ready_for_local_init_op) if self._local_init_op is None: self._local_init_op = Scaffold.get_or_default( 'local_init_op', ops.GraphKeys.LOCAL_INIT_OP, Scaffold.default_local_init_op) if self._summary_op is None: self._summary_op = Scaffold.get_or_default('summary_op', ops.GraphKeys.SUMMARY_OP, summary.merge_all) # pylint: disable=g-long-lambda if self._saver is None: self._saver = training_saver._get_saver_or_default() # pylint: disable=protected-access # pylint: enable=g-long-lambda if isinstance(self._saver, trackable_util.Checkpoint): self._saver = training_saver.Saver( var_list=graph_view.ObjectGraphView( self._saver).frozen_saveable_objects(), sharded=True) else: self._saver.build() ops.get_default_graph().finalize() logging.info('Graph was finalized.') return self @property def init_fn(self): return self._init_fn @property def init_op(self): return self._init_op @property def ready_op(self): return self._ready_op @property def ready_for_local_init_op(self): return self._ready_for_local_init_op @property def local_init_op(self): return self._local_init_op @property def local_init_feed_dict(self): return self._local_init_feed_dict @property def summary_op(self): return self._summary_op @property def saver(self): return self._saver @property def init_feed_dict(self): return self._init_feed_dict @staticmethod def get_or_default(arg_name, collection_key, default_constructor): """Get from cache or create a default operation.""" elements = ops.get_collection(collection_key) if elements: if len(elements) > 1: raise RuntimeError( 'More than one item in the collection "%s". ' 'Please indicate which one to use by passing it to ' 'the tf.Scaffold constructor as: ' 'tf.Scaffold(%s=item to use)', collection_key, arg_name) return elements[0] op = default_constructor() if op is not None: ops.add_to_collection(collection_key, op) return op @staticmethod def default_local_init_op(): """Returns an op that groups the default local init ops. This op is used during session initialization when a Scaffold is initialized without specifying the local_init_op arg. It includes `tf.compat.v1.local_variables_initializer`, `tf.compat.v1.tables_initializer`, and also initializes local session resources. Returns: The default Scaffold local init op. """ return control_flow_ops.group( variables.local_variables_initializer(), lookup_ops.tables_initializer(), resources.initialize_resources(resources.local_resources())) def _create_monitored_session_with_worker_context( worker_context, # pylint: disable=missing-docstring scaffold, checkpoint_dir=None, hooks=None, chief_only_hooks=None, save_checkpoint_secs=None, save_summaries_steps=None, save_summaries_secs=None, config=None, stop_grace_period_secs=120, log_step_count_steps=100, max_wait_secs=7200, save_checkpoint_steps=None, summary_dir=None, save_graph_def=True): all_hooks = [] if hooks: all_hooks.extend(hooks) if chief_only_hooks and worker_context.is_chief: all_hooks.extend(chief_only_hooks) # We need to call save or summary ops on all workers since these ops may # contain collective ops, only running save ops on some workers would make # collective ops hang. Therefore on those workers that don't need to actually # write checkpoints or summaries, we let them write to a temp directory. # pylint: disable=protected-access if type( worker_context._strategy).__name__ in ('CollectiveAllReduceStrategy', 'CollectiveAllReduceStrategyV1', 'MultiWorkerMirroredStrategy'): if worker_context.task_type: tmpdir = 'tmp_%s_%d' % (worker_context.task_type, worker_context.task_id) else: tmpdir = 'tmp' if save_checkpoint_secs: logging.warning('Collective ops may deadlock with ' '`save_checkpoints_secs` please use ' '`save_checkpoint_steps` instead. Clearing ' '`save_checkpoint_secs` and setting ' '`save_checkpoint_steps` to 1000 now.') save_checkpoint_secs = None save_checkpoint_steps = 1000 if save_summaries_secs: logging.warning('Collective ops may run out of sync with' '`save_summaries_secs`, please use ' '`save_summaries_steps` instead.') else: tmpdir = None summary_dir = summary_dir or checkpoint_dir if summary_dir and log_step_count_steps and log_step_count_steps > 0: if worker_context.should_save_summary: all_hooks.append( basic_session_run_hooks.StepCounterHook( output_dir=summary_dir, every_n_steps=log_step_count_steps)) elif tmpdir: all_hooks.append( basic_session_run_hooks.StepCounterHook( output_dir=os.path.join(summary_dir, tmpdir), every_n_steps=log_step_count_steps)) if (((save_summaries_steps and save_summaries_steps > 0) or (save_summaries_secs and save_summaries_secs > 0)) and summary_dir): if worker_context.should_save_summary: all_hooks.append( basic_session_run_hooks.SummarySaverHook( scaffold=scaffold, save_steps=save_summaries_steps, save_secs=save_summaries_secs, output_dir=summary_dir)) elif tmpdir: all_hooks.append( basic_session_run_hooks.SummarySaverHook( scaffold=scaffold, save_steps=save_summaries_steps, save_secs=save_summaries_secs, output_dir=os.path.join(summary_dir, tmpdir))) if (((save_checkpoint_secs and save_checkpoint_secs > 0) or (save_checkpoint_steps and save_checkpoint_steps > 0)) and checkpoint_dir): if worker_context.should_checkpoint: all_hooks.append( basic_session_run_hooks.CheckpointSaverHook( checkpoint_dir, save_steps=save_checkpoint_steps, save_secs=save_checkpoint_secs, scaffold=scaffold, save_graph_def=save_graph_def)) elif tmpdir: all_hooks.append( basic_session_run_hooks.CheckpointSaverHook( os.path.join(checkpoint_dir, tmpdir), save_steps=save_checkpoint_steps, save_secs=save_checkpoint_secs, scaffold=scaffold, save_graph_def=save_graph_def)) logging.info('all_hooks %r', all_hooks) session_creator = worker_context.session_creator( scaffold, config=config, checkpoint_dir=checkpoint_dir, max_wait_secs=max_wait_secs) return MonitoredSession( session_creator=session_creator, hooks=all_hooks, stop_grace_period_secs=stop_grace_period_secs) @tf_export(v1=['train.MonitoredTrainingSession']) def MonitoredTrainingSession( master='', # pylint: disable=invalid-name is_chief=True, checkpoint_dir=None, scaffold=None, hooks=None, chief_only_hooks=None, save_checkpoint_secs=USE_DEFAULT, save_summaries_steps=USE_DEFAULT, save_summaries_secs=USE_DEFAULT, config=None, stop_grace_period_secs=120, log_step_count_steps=100, max_wait_secs=7200, save_checkpoint_steps=USE_DEFAULT, summary_dir=None, save_graph_def=True): """Creates a `MonitoredSession` for training. For a chief, this utility sets proper session initializer/restorer. It also creates hooks related to checkpoint and summary saving. For workers, this utility sets proper session creator which waits for the chief to initialize/restore. Please check `tf.compat.v1.train.MonitoredSession` for more information. @compatibility(TF2) This API is not compatible with eager execution and `tf.function`. To migrate to TF2, rewrite the code to be compatible with eager execution. Check the [migration guide](https://www.tensorflow.org/guide/migrate#1_replace_v1sessionrun_calls) on replacing `Session.run` calls. In Keras, session hooks can be replaced by Callbacks e.g. [logging hook notebook]( https://github.com/tensorflow/docs/blob/master/site/en/guide/migrate/logging_stop_hook.ipynb) For more details please read [Better performance with tf.function](https://www.tensorflow.org/guide/function). @end_compatibility Args: master: `String` the TensorFlow master to use. is_chief: If `True`, it will take care of initialization and recovery the underlying TensorFlow session. If `False`, it will wait on a chief to initialize or recover the TensorFlow session. checkpoint_dir: A string. Optional path to a directory where to restore variables. scaffold: A `Scaffold` used for gathering or building supportive ops. If not specified, a default one is created. It's used to finalize the graph. hooks: Optional list of `SessionRunHook` objects. chief_only_hooks: list of `SessionRunHook` objects. Activate these hooks if `is_chief==True`, ignore otherwise. save_checkpoint_secs: The frequency, in seconds, that a checkpoint is saved using a default checkpoint saver. If both `save_checkpoint_steps` and `save_checkpoint_secs` are set to `None`, then the default checkpoint saver isn't used. If both are provided, then only `save_checkpoint_secs` is used. Default 600. save_summaries_steps: The frequency, in number of global steps, that the summaries are written to disk using a default summary saver. If both `save_summaries_steps` and `save_summaries_secs` are set to `None`, then the default summary saver isn't used. Default 100. save_summaries_secs: The frequency, in secs, that the summaries are written to disk using a default summary saver. If both `save_summaries_steps` and `save_summaries_secs` are set to `None`, then the default summary saver isn't used. Default not enabled. config: an instance of `tf.compat.v1.ConfigProto` proto used to configure the session. It's the `config` argument of constructor of `tf.compat.v1.Session`. stop_grace_period_secs: Number of seconds given to threads to stop after `close()` has been called. log_step_count_steps: The frequency, in number of global steps, that the global step/sec is logged. max_wait_secs: Maximum time workers should wait for the session to become available. This should be kept relatively short to help detect incorrect code, but sometimes may need to be increased if the chief takes a while to start up. save_checkpoint_steps: The frequency, in number of global steps, that a checkpoint is saved using a default checkpoint saver. If both `save_checkpoint_steps` and `save_checkpoint_secs` are set to `None`, then the default checkpoint saver isn't used. If both are provided, then only `save_checkpoint_secs` is used. Default not enabled. summary_dir: A string. Optional path to a directory where to save summaries. If None, checkpoint_dir is used instead. save_graph_def: Whether to save the GraphDef and MetaGraphDef to `checkpoint_dir`. The GraphDef is saved after the session is created as `graph.pbtxt`. MetaGraphDefs are saved out for every checkpoint as `model.ckpt-*.meta`. Returns: A `MonitoredSession` object. """ if save_summaries_steps == USE_DEFAULT and save_summaries_secs == USE_DEFAULT: save_summaries_steps = 100 save_summaries_secs = None elif save_summaries_secs == USE_DEFAULT: save_summaries_secs = None elif save_summaries_steps == USE_DEFAULT: save_summaries_steps = None if (save_checkpoint_steps == USE_DEFAULT and save_checkpoint_secs == USE_DEFAULT): save_checkpoint_steps = None save_checkpoint_secs = 600 elif save_checkpoint_secs == USE_DEFAULT: save_checkpoint_secs = None elif save_checkpoint_steps == USE_DEFAULT: save_checkpoint_steps = None scaffold = scaffold or Scaffold() worker_context = distribute_coordinator_context.get_current_worker_context() if worker_context: return _create_monitored_session_with_worker_context( worker_context, scaffold, checkpoint_dir=checkpoint_dir, hooks=hooks, chief_only_hooks=chief_only_hooks, save_checkpoint_secs=save_checkpoint_secs, save_summaries_steps=save_summaries_steps, save_summaries_secs=save_summaries_secs, config=config, stop_grace_period_secs=stop_grace_period_secs, log_step_count_steps=log_step_count_steps, max_wait_secs=max_wait_secs, save_checkpoint_steps=save_checkpoint_steps, summary_dir=summary_dir, save_graph_def=save_graph_def) if not is_chief: session_creator = WorkerSessionCreator( scaffold=scaffold, master=master, config=config, max_wait_secs=max_wait_secs) return MonitoredSession( session_creator=session_creator, hooks=hooks or [], stop_grace_period_secs=stop_grace_period_secs) all_hooks = [] if chief_only_hooks: all_hooks.extend(chief_only_hooks) session_creator = ChiefSessionCreator( scaffold=scaffold, checkpoint_dir=checkpoint_dir, master=master, config=config) summary_dir = summary_dir or checkpoint_dir if summary_dir: if log_step_count_steps and log_step_count_steps > 0: all_hooks.append( basic_session_run_hooks.StepCounterHook( output_dir=summary_dir, every_n_steps=log_step_count_steps)) if (save_summaries_steps and save_summaries_steps > 0) or (save_summaries_secs and save_summaries_secs > 0): all_hooks.append( basic_session_run_hooks.SummarySaverHook( scaffold=scaffold, save_steps=save_summaries_steps, save_secs=save_summaries_secs, output_dir=summary_dir)) if checkpoint_dir: if (save_checkpoint_secs and save_checkpoint_secs > 0) or (save_checkpoint_steps and save_checkpoint_steps > 0): all_hooks.append( basic_session_run_hooks.CheckpointSaverHook( checkpoint_dir, save_steps=save_checkpoint_steps, save_secs=save_checkpoint_secs, scaffold=scaffold, save_graph_def=save_graph_def)) if hooks: all_hooks.extend(hooks) return MonitoredSession( session_creator=session_creator, hooks=all_hooks, stop_grace_period_secs=stop_grace_period_secs) @tf_export(v1=['train.SessionCreator']) @six.add_metaclass(abc.ABCMeta) class SessionCreator(object): """A factory for tf.Session.""" @abc.abstractmethod def create_session(self): raise NotImplementedError( 'create_session is not implemented for {}.'.format(self)) @tf_export(v1=['train.ChiefSessionCreator']) class ChiefSessionCreator(SessionCreator): """Creates a tf.compat.v1.Session for a chief.""" def __init__(self, scaffold=None, master='', config=None, checkpoint_dir=None, checkpoint_filename_with_path=None): """Initializes a chief session creator. Args: scaffold: A `Scaffold` used for gathering or building supportive ops. If not specified a default one is created. It's used to finalize the graph. master: `String` representation of the TensorFlow master to use. config: `ConfigProto` proto used to configure the session. checkpoint_dir: A string. Optional path to a directory where to restore variables. checkpoint_filename_with_path: Full file name path to the checkpoint file. """ self._checkpoint_dir = checkpoint_dir self._checkpoint_filename_with_path = checkpoint_filename_with_path self._scaffold = scaffold or Scaffold() self._session_manager = None self._master = master self._config = config def _get_session_manager(self): """Gets or creates a SessionManager.""" if self._session_manager: return self._session_manager self._session_manager = sm.SessionManager( local_init_op=self._scaffold.local_init_op, local_init_feed_dict=self._scaffold.local_init_feed_dict, ready_op=self._scaffold.ready_op, ready_for_local_init_op=self._scaffold.ready_for_local_init_op, graph=ops.get_default_graph()) return self._session_manager def create_session(self): self._scaffold.finalize() return self._get_session_manager().prepare_session( self._master, saver=self._scaffold.saver, checkpoint_dir=self._checkpoint_dir, checkpoint_filename_with_path=self._checkpoint_filename_with_path, config=self._config, init_op=self._scaffold.init_op, init_feed_dict=self._scaffold.init_feed_dict, init_fn=self._scaffold.init_fn) @tf_export(v1=['train.WorkerSessionCreator']) class WorkerSessionCreator(SessionCreator): """Creates a tf.compat.v1.Session for a worker.""" def __init__(self, scaffold=None, master='', config=None, max_wait_secs=30 * 60): """Initializes a worker session creator. Args: scaffold: A `Scaffold` used for gathering or building supportive ops. If not specified a default one is created. It's used to finalize the graph. master: `String` representation of the TensorFlow master to use. config: `ConfigProto` proto used to configure the session. max_wait_secs: Maximum time to wait for the session to become available. """ self._scaffold = scaffold or Scaffold() self._session_manager = None self._master = master self._config = config self._max_wait_secs = max_wait_secs def _get_session_manager(self): """Gets or creates a SessionManager.""" if self._session_manager: return self._session_manager self._session_manager = sm.SessionManager( local_init_op=self._scaffold.local_init_op, local_init_feed_dict=self._scaffold.local_init_feed_dict, ready_op=self._scaffold.ready_op, ready_for_local_init_op=self._scaffold.ready_for_local_init_op, graph=ops.get_default_graph()) return self._session_manager def create_session(self): self._scaffold.finalize() return self._get_session_manager().wait_for_session( self._master, config=self._config, max_wait_secs=self._max_wait_secs) class _MonitoredSession(object): """See `MonitoredSession` or `SingularMonitoredSession`.""" def __init__(self, session_creator, hooks, should_recover, stop_grace_period_secs=120): """Sets up a Monitored or Hooked Session. Args: session_creator: A factory object to create session. Typically a `ChiefSessionCreator` or a `WorkerSessionCreator`. hooks: An iterable of `SessionRunHook' objects. should_recover: A bool. Indicates whether to recover from `AbortedError` and `UnavailableError` or not. stop_grace_period_secs: Number of seconds given to threads to stop after `close()` has been called. """ self._graph_was_finalized = ops.get_default_graph().finalized self._hooks = hooks or [] for h in self._hooks: h.begin() worker_context = distribute_coordinator_context.get_current_worker_context() if not session_creator and worker_context: session_creator = worker_context.session_creator() # Create the session. self._coordinated_creator = self._CoordinatedSessionCreator( session_creator=session_creator or ChiefSessionCreator(), hooks=self._hooks, stop_grace_period_secs=stop_grace_period_secs) if should_recover: self._sess = _RecoverableSession(self._coordinated_creator) else: self._sess = self._coordinated_creator.create_session() @property def graph(self): """The graph that was launched in this session.""" if self._tf_sess() is None: return None return self._tf_sess().graph def run(self, fetches, feed_dict=None, options=None, run_metadata=None): """Run ops in the monitored session. This method is completely compatible with the `tf.Session.run()` method. Args: fetches: Same as `tf.Session.run()`. feed_dict: Same as `tf.Session.run()`. options: Same as `tf.Session.run()`. run_metadata: Same as `tf.Session.run()`. Returns: Same as `tf.Session.run()`. """ return self._sess.run( fetches, feed_dict=feed_dict, options=options, run_metadata=run_metadata) def run_step_fn(self, step_fn): """Run ops using a step function. Args: step_fn: A function or a method with a single argument of type `StepContext`. The function may use methods of the argument to perform computations with access to a raw session. The returned value of the `step_fn` will be returned from `run_step_fn`, unless a stop is requested. In that case, the next `should_stop` call will return True. Example usage: ```python with tf.Graph().as_default(): c = tf.compat.v1.placeholder(dtypes.float32) v = tf.add(c, 4.0) w = tf.add(c, 0.5) def step_fn(step_context): a = step_context.session.run(fetches=v, feed_dict={c: 0.5}) if a <= 4.5: step_context.request_stop() return step_context.run_with_hooks(fetches=w, feed_dict={c: 0.1}) with tf.MonitoredSession() as session: while not session.should_stop(): a = session.run_step_fn(step_fn) ``` Hooks interact with the `run_with_hooks()` call inside the `step_fn` as they do with a `MonitoredSession.run` call. Returns: Returns the returned value of `step_fn`. Raises: StopIteration: if `step_fn` has called `request_stop()`. It may be caught by `with tf.MonitoredSession()` to close the session. ValueError: if `step_fn` doesn't have a single argument called `step_context`. It may also optionally have `self` for cases when it belongs to an object. """ step_fn_arguments = function_utils.fn_args(step_fn) if step_fn_arguments != ('step_context',) and step_fn_arguments != ( 'self', 'step_context', ): raise ValueError( '`step_fn` may either have one `step_context` argument, or' ' `self` and `step_context` arguments if it\'s an instance' ' method. Got {} instead.'.format(step_fn_arguments)) # `self._sess` is either `_RecoverableSession` or a `_CoordinatedSession`. # Setting `run_with_hooks` to `None` will cause `run_with_hooks` to be # `_CoordinatedSession.run` downstream in either case. This allows # `_PREEMPTION_ERRORS` to propage from within `step_fn` to # `_RecoverableSession.run_step_fn`. return self._sess.run_step_fn(step_fn, self._tf_sess(), run_with_hooks=None) class StepContext(object): """Control flow instrument for the `step_fn` from `run_step_fn()`. Users of `step_fn` may perform `run()` calls without running hooks by accessing the `session`. A `run()` call with hooks may be performed using `run_with_hooks()`. Computation flow can be interrupted using `request_stop()`. """ def __init__(self, session, run_with_hooks_fn): """Initializes the `step_context` argument for a `step_fn` invocation. Args: session: An instance of `tf.compat.v1.Session`. run_with_hooks_fn: A function for running fetches and hooks. """ self._session = session self._run_with_hooks_fn = run_with_hooks_fn @property def session(self): return self._session def run_with_hooks(self, *args, **kwargs): """Same as `MonitoredSession.run`. Accepts the same arguments.""" return self._run_with_hooks_fn(*args, **kwargs) def request_stop(self): """Exit the training loop by causing `should_stop()` to return `True`. Causes `step_fn` to exit by raising an exception. Raises: StopIteration """ raise StopIteration('step_fn has requested the iterations to stop.') def should_stop(self): return self._sess is None or self._sess.should_stop() def close(self): self._close_internal() def __enter__(self): return self def __exit__(self, exception_type, exception_value, traceback): if exception_type in [errors.OutOfRangeError, StopIteration]: exception_type = None self._close_internal(exception_type) # __exit__ should return True to suppress an exception. return exception_type is None class _CoordinatedSessionCreator(SessionCreator): """Factory for _CoordinatedSession.""" def __init__(self, session_creator, hooks, stop_grace_period_secs): self._session_creator = session_creator self._hooks = hooks self.coord = None self.tf_sess = None self._stop_grace_period_secs = stop_grace_period_secs def create_session(self): """Creates a coordinated session.""" # Keep the tf_sess for unit testing. self.tf_sess = self._session_creator.create_session() # We don't want coordinator to suppress any exception. self.coord = coordinator.Coordinator(clean_stop_exception_types=[]) if ops.get_collection(ops.GraphKeys.QUEUE_RUNNERS): queue_runner.start_queue_runners(sess=self.tf_sess, coord=self.coord) # Inform the hooks that a new session has been created. for hook in self._hooks: hook.after_create_session(self.tf_sess, self.coord) return _CoordinatedSession( _HookedSession(self.tf_sess, self._hooks), self.coord, self._stop_grace_period_secs) def _close_internal(self, exception_type=None): try: if not exception_type: for h in self._hooks: h.end(self._coordinated_creator.tf_sess) finally: try: if self._sess is None: raise RuntimeError('Session is already closed.') self._sess.close() finally: self._sess = None self._coordinated_creator.tf_sess = None self._coordinated_creator.coord = None if not self._graph_was_finalized: ops.get_default_graph()._unsafe_unfinalize() # pylint: disable=protected-access def _is_closed(self): """Return True if the monitored session is closed. For tests only. Returns: A boolean. """ return self._coordinated_creator.tf_sess is None def _tf_sess(self): """Return underlying tf.compat.v1.Session object. Warning: accessing the returned object in user code is likely to cause races or "flaky tests". Returns: A tf.compat.v1.Session object. """ return self._coordinated_creator.tf_sess @tf_export(v1=['train.MonitoredSession']) class MonitoredSession(_MonitoredSession): """Session-like object that handles initialization, recovery and hooks. Example usage: ```python saver_hook = CheckpointSaverHook(...) summary_hook = SummarySaverHook(...) with MonitoredSession(session_creator=ChiefSessionCreator(...), hooks=[saver_hook, summary_hook]) as sess: while not sess.should_stop(): sess.run(train_op) ``` Initialization: At creation time the monitored session does following things in given order: * calls `hook.begin()` for each given hook * finalizes the graph via `scaffold.finalize()` * create session * initializes the model via initialization ops provided by `Scaffold` * restores variables if a checkpoint exists * launches queue runners * calls `hook.after_create_session()` Run: When `run()` is called, the monitored session does following things: * calls `hook.before_run()` * calls TensorFlow `session.run()` with merged fetches and feed_dict * calls `hook.after_run()` * returns result of `session.run()` asked by user * if `AbortedError` or `UnavailableError` occurs, it recovers or reinitializes the session before executing the run() call again Exit: At the `close()`, the monitored session does following things in order: * calls `hook.end()` * closes the queue runners and the session * suppresses `OutOfRange` error which indicates that all inputs have been processed if the monitored_session is used as a context How to set `tf.compat.v1.Session` arguments: * In most cases you can set session arguments as follows: ```python MonitoredSession( session_creator=ChiefSessionCreator(master=..., config=...)) ``` * In distributed setting for a non-chief worker, you can use following: ```python MonitoredSession( session_creator=WorkerSessionCreator(master=..., config=...)) ``` See `MonitoredTrainingSession` for an example usage based on chief or worker. Note: This is not a `tf.compat.v1.Session`. For example, it cannot do following: * it cannot be set as default session. * it cannot be sent to saver.save. * it cannot be sent to tf.train.start_queue_runners. @compatibility(TF2) This API is not compatible with eager execution and `tf.function`. To migrate to TF2, rewrite the code to be compatible with eager execution. Check the [migration guide](https://www.tensorflow.org/guide/migrate#1_replace_v1sessionrun_calls) on replacing `Session.run` calls. In Keras, session hooks can be replaced by Callbacks e.g. [logging hook notebook]( https://github.com/tensorflow/docs/blob/master/site/en/guide/migrate/logging_stop_hook.ipynb) For more details please read [Better performance with tf.function](https://www.tensorflow.org/guide/function). @end_compatibility Args: session_creator: A factory object to create session. Typically a `ChiefSessionCreator` which is the default one. hooks: An iterable of `SessionRunHook' objects. Returns: A MonitoredSession object. """ def __init__(self, session_creator=None, hooks=None, stop_grace_period_secs=120): super(MonitoredSession, self).__init__( session_creator, hooks, should_recover=True, stop_grace_period_secs=stop_grace_period_secs) @tf_export(v1=['train.SingularMonitoredSession']) class SingularMonitoredSession(_MonitoredSession): """Session-like object that handles initialization, restoring, and hooks. Please note that this utility is not recommended for distributed settings. For distributed settings, please use `tf.compat.v1.train.MonitoredSession`. The differences between `MonitoredSession` and `SingularMonitoredSession` are: * `MonitoredSession` handles `AbortedError` and `UnavailableError` for distributed settings, but `SingularMonitoredSession` does not. * `MonitoredSession` can be created in `chief` or `worker` modes. `SingularMonitoredSession` is always created as `chief`. * You can access the raw `tf.compat.v1.Session` object used by `SingularMonitoredSession`, whereas in MonitoredSession the raw session is private. This can be used: - To `run` without hooks. - To save and restore. * All other functionality is identical. Example usage: ```python saver_hook = CheckpointSaverHook(...) summary_hook = SummarySaverHook(...) with SingularMonitoredSession(hooks=[saver_hook, summary_hook]) as sess: while not sess.should_stop(): sess.run(train_op) ``` Initialization: At creation time the hooked session does following things in given order: * calls `hook.begin()` for each given hook * finalizes the graph via `scaffold.finalize()` * create session * initializes the model via initialization ops provided by `Scaffold` * restores variables if a checkpoint exists * launches queue runners Run: When `run()` is called, the hooked session does following things: * calls `hook.before_run()` * calls TensorFlow `session.run()` with merged fetches and feed_dict * calls `hook.after_run()` * returns result of `session.run()` asked by user Exit: At the `close()`, the hooked session does following things in order: * calls `hook.end()` * closes the queue runners and the session * suppresses `OutOfRange` error which indicates that all inputs have been processed if the `SingularMonitoredSession` is used as a context. @compatibility(TF2) This API is not compatible with eager execution and `tf.function`. To migrate to TF2, rewrite the code to be compatible with eager execution. Check the [migration guide](https://www.tensorflow.org/guide/migrate#1_replace_v1sessionrun_calls) on replacing `Session.run` calls. In Keras, session hooks can be replaced by Callbacks e.g. [logging hook notebook]( https://github.com/tensorflow/docs/blob/master/site/en/guide/migrate/logging_stop_hook.ipynb) For more details please read [Better performance with tf.function](https://www.tensorflow.org/guide/function). @end_compatibility """ def __init__(self, hooks=None, scaffold=None, master='', config=None, checkpoint_dir=None, stop_grace_period_secs=120, checkpoint_filename_with_path=None): """Creates a SingularMonitoredSession. Args: hooks: An iterable of `SessionRunHook' objects. scaffold: A `Scaffold` used for gathering or building supportive ops. If not specified a default one is created. It's used to finalize the graph. master: `String` representation of the TensorFlow master to use. config: `ConfigProto` proto used to configure the session. checkpoint_dir: A string. Optional path to a directory where to restore variables. stop_grace_period_secs: Number of seconds given to threads to stop after `close()` has been called. checkpoint_filename_with_path: A string. Optional path to a checkpoint file from which to restore variables. """ session_creator = ChiefSessionCreator( scaffold=scaffold, master=master, config=config, checkpoint_dir=checkpoint_dir, checkpoint_filename_with_path=checkpoint_filename_with_path) super(SingularMonitoredSession, self).__init__( session_creator, hooks, should_recover=False, stop_grace_period_secs=stop_grace_period_secs) def raw_session(self): """Returns underlying `TensorFlow.Session` object.""" return self._tf_sess() class _WrappedSession(object): """Wrapper around a `tf.compat.v1.Session`. This wrapper is used as a base class for various session wrappers that provide additional functionality such as monitoring, coordination, and recovery. In addition to the methods exported by `SessionInterface` the wrapper provides a method to check for stop and never raises exceptions from calls to `close()`. """ def __init__(self, sess): """Creates a `_WrappedSession`. Args: sess: A `tf.compat.v1.Session` or `_WrappedSession` object. The wrapped session. """ self._sess = sess self._wrapped_is_stoppable = isinstance(self._sess, _WrappedSession) @property def graph(self): return self._sess.graph @property def sess_str(self): return self._sess.sess_str def should_stop(self): """Return true if this session should not be used anymore. Always return True if the session was closed. Returns: True if the session should stop, False otherwise. """ if self._check_stop(): return True if self._sess: return self._wrapped_is_stoppable and self._sess.should_stop() return True def _check_stop(self): """Hook for subclasses to provide their own stop condition. Returns: True if the session should stop, False otherwise. """ return False def close(self): if self._sess: try: self._sess.close() except _PREEMPTION_ERRORS as e: logging.error( 'An error occurred when attempting to close the ' 'session. This may be due to a preemption in a ' 'connected worker or parameter server. Error: %s', e) finally: self._sess = None def run(self, *args, **kwargs): return self._sess.run(*args, **kwargs) def run_step_fn(self, step_fn, raw_session, run_with_hooks): # `_RecoverableSession` sets `run_with_hooks` to `_CoordinatedSession.run`. # It is `None` when called from `_CoordinatedSession`. In that case # `self.run` is `_CoordinatedSession.run`. run_with_hooks = run_with_hooks or self.run return step_fn(_MonitoredSession.StepContext(raw_session, run_with_hooks)) class _RecoverableSession(_WrappedSession): """A wrapped session that recreates a session upon certain kinds of errors. The constructor is passed a SessionCreator object, not a session. Calls to `run()` are delegated to the wrapped session. If a call raises the exception `tf.errors.AbortedError` or `tf.errors.UnavailableError`, the wrapped session is closed, and a new one is created by calling the factory again. """ def __init__(self, sess_creator): """Create a new `_RecoverableSession`. The value returned by calling `sess_creator.create_session()` will be the session wrapped by this recoverable session. Args: sess_creator: A 'SessionCreator' to be wrapped by recoverable. """ self._sess_creator = sess_creator _WrappedSession.__init__(self, self._create_session()) def _create_session(self): while True: try: return self._sess_creator.create_session() except _PREEMPTION_ERRORS as e: logging.info( 'An error was raised while a session was being created. ' 'This may be due to a preemption of a connected worker ' 'or parameter server. A new session will be created. ' 'This error may also occur due to a gRPC failure caused ' 'by high memory or network bandwidth usage in the ' 'parameter servers. If this error occurs repeatedly, try ' 'increasing the number of parameter servers assigned to ' 'the job. Error: %s', e) def _check_stop(self): try: if self._sess: return self._sess._check_stop() # pylint: disable=protected-access else: return True except _PREEMPTION_ERRORS as e: logging.info( 'An error was raised while considering whether the ' 'session is complete. This may be due to a preemption in ' 'a connected worker or parameter server. The current ' 'session will be closed and a new session will be ' 'created. This error may also occur due to a gRPC failure ' 'caused by high memory or network bandwidth usage in the ' 'parameter servers. If this error occurs repeatedly, try ' 'increasing the number of parameter servers assigned to ' 'the job. Error: %s', e) self.close() self._sess = self._create_session() # Since we have just recreated the session, the overall computation should # not stop: return False except Exception: # pylint: disable=broad-except # `should_stop` should return True instead of raising an exception. return True def run(self, fetches, feed_dict=None, options=None, run_metadata=None): while True: try: if not self._sess: self._sess = self._create_session() return self._sess.run( fetches, feed_dict=feed_dict, options=options, run_metadata=run_metadata) except _PREEMPTION_ERRORS as e: logging.info( 'An error was raised. This may be due to a preemption in ' 'a connected worker or parameter server. The current ' 'session will be closed and a new session will be ' 'created. This error may also occur due to a gRPC failure ' 'caused by high memory or network bandwidth usage in the ' 'parameter servers. If this error occurs repeatedly, try ' 'increasing the number of parameter servers assigned to ' 'the job. Error: %s', e) self.close() self._sess = None def run_step_fn(self, step_fn, raw_session, run_with_hooks): while True: try: if not self._sess: self._sess = self._create_session() run_with_hooks = self._sess.run return self._sess.run_step_fn(step_fn, raw_session, run_with_hooks) except _PREEMPTION_ERRORS as e: logging.info( 'An error was raised. This may be due to a preemption in ' 'a connected worker or parameter server. The current ' 'session will be closed and a new session will be ' 'created. This error may also occur due to a gRPC failure ' 'caused by high memory or network bandwidth usage in the ' 'parameter servers. If this error occurs repeatedly, try ' 'increasing the number of parameter servers assigned to ' 'the job. Error: %s', e) self.close() self._sess = None class _CoordinatedSession(_WrappedSession): """A wrapped session that works with a `tf.Coordinator`. Calls to `run()` are delegated to the wrapped session. If a call raises an exception, the exception is reported to the coordinator. In addition, after each call to `run()` this session ask the coordinator if the session should stop. In that case it will join all the threads registered with the coordinator before returning. If the coordinator was requested to stop with an exception, that exception will be re-raised from the call to `run()`. """ def __init__(self, sess, coord, stop_grace_period_secs=120): """Create a new `_CoordinatedSession`. Args: sess: A `tf.compat.v1.Session` object. The wrapped session. coord: A `tf.train.Coordinator` object. stop_grace_period_secs: Number of seconds given to threads to stop after `close()` has been called. """ _WrappedSession.__init__(self, sess) self._coord = coord self._stop_grace_period_secs = stop_grace_period_secs def _check_stop(self): # If the coordinator was asked to stop due to an exception, then it needs # to be propagated to this stack. self._coord.raise_requested_exception() # At this point, no exceptions are recorded in the coordinator. return self._coord.should_stop() def close(self): self._coord.request_stop() try: self._coord.join( stop_grace_period_secs=self._stop_grace_period_secs, ignore_live_threads=True) finally: try: _WrappedSession.close(self) except Exception: # pylint: disable=broad-except # We intentionally suppress exceptions from the close() here since # useful exceptions are already reported by join(). pass def run(self, *args, **kwargs): try: return self._sess.run(*args, **kwargs) except _PREEMPTION_ERRORS: raise except Exception: # pylint: disable=broad-except # A non-preemption error could have been caused by a preemption error # in the coordinator. If this is the case, raise that exception instead, # since it's the root cause. Otherwise, stick to the `original_exc_info`. original_exc_info = sys.exc_info() try: self._coord.raise_requested_exception() except _PREEMPTION_ERRORS: raise except Exception: # pylint: disable=broad-except raise six.reraise(*original_exc_info) else: raise six.reraise(*original_exc_info) class _HookedSession(_WrappedSession): """A _WrappedSession that calls hooks during calls to run(). The list of hooks to call is passed in the constructor. Before each call to `run()` the session calls the `before_run()` method of the hooks, which can return additional ops or tensors to run. These are added to the arguments of the call to `run()`. When the `run()` call finishes, the session calls the `after_run()` methods of the hooks, passing the values returned by the `run()` call corresponding to the ops and tensors that each hook requested. If any call to the hooks, requests stop via run_context the session will be marked as needing to stop and its `should_stop()` method will now return `True`. """ def __init__(self, sess, hooks): """Initializes a _HookedSession object. Args: sess: A `tf.compat.v1.Session` or a `_WrappedSession` object. hooks: An iterable of `SessionRunHook' objects. """ _WrappedSession.__init__(self, sess) self._hooks = hooks self._should_stop = False def _check_stop(self): """See base class.""" return self._should_stop def run(self, fetches, feed_dict=None, options=None, run_metadata=None): """See base class.""" if self.should_stop(): raise RuntimeError('Run called even after should_stop requested.') actual_fetches = {'caller': fetches} run_context = session_run_hook.SessionRunContext( original_args=session_run_hook.SessionRunArgs(fetches, feed_dict), session=self._sess) options = options or config_pb2.RunOptions() feed_dict = self._call_hook_before_run(run_context, actual_fetches, feed_dict, options) # Do session run. run_metadata = run_metadata or config_pb2.RunMetadata() outputs = _WrappedSession.run( self, fetches=actual_fetches, feed_dict=feed_dict, options=options, run_metadata=run_metadata) for hook in self._hooks: hook.after_run( run_context, session_run_hook.SessionRunValues( results=outputs[hook] if hook in outputs else None, options=options, run_metadata=run_metadata)) self._should_stop = self._should_stop or run_context.stop_requested return outputs['caller'] def _call_hook_before_run(self, run_context, fetch_dict, user_feed_dict, options): """Calls hooks.before_run and handles requests from hooks.""" hook_feeds = {} for hook in self._hooks: request = hook.before_run(run_context) if request is not None: if request.fetches is not None: fetch_dict[hook] = request.fetches if request.feed_dict: self._raise_if_feeds_intersects(hook_feeds, request.feed_dict, 'Same tensor is fed by two hooks.') hook_feeds.update(request.feed_dict) if request.options: self._merge_run_options(options, request.options) if not hook_feeds: return user_feed_dict if not user_feed_dict: return hook_feeds self._raise_if_feeds_intersects( user_feed_dict, hook_feeds, 'Same tensor is fed by a SessionRunHook and user.') hook_feeds.update(user_feed_dict) return hook_feeds def _raise_if_feeds_intersects(self, feeds1, feeds2, message): intersection = set(feeds1.keys()) & set(feeds2.keys()) if intersection: raise RuntimeError(message + ' Conflict(s): ' + str(list(intersection))) def _merge_run_options(self, options, incoming_options): """Merge two instances of RunOptions into the first one. During the merger, the numerical fields including trace_level, timeout_in_ms, inter_op_thread_pool are set to the larger one of the two. The boolean value is set to the logical OR of the two. debug_tensor_watch_opts of the original options is extended with that from the incoming one. Args: options: The options to merge into. incoming_options: The options to be merged into the first argument. """ options.trace_level = max(options.trace_level, incoming_options.trace_level) options.timeout_in_ms = max(options.timeout_in_ms, incoming_options.timeout_in_ms) options.inter_op_thread_pool = max(options.inter_op_thread_pool, incoming_options.inter_op_thread_pool) options.output_partition_graphs = max( options.output_partition_graphs, incoming_options.output_partition_graphs) options.debug_options.debug_tensor_watch_opts.extend( incoming_options.debug_options.debug_tensor_watch_opts) options.debug_options.reset_disk_byte_usage = ( options.debug_options.reset_disk_byte_usage or incoming_options.debug_options.reset_disk_byte_usage) options.report_tensor_allocations_upon_oom = ( options.report_tensor_allocations_upon_oom or incoming_options.report_tensor_allocations_upon_oom)