Add RedisDataStore (#295)

* GraphManager.set_session also sets self.sess

* make sure that GraphManager.fetch_from_worker uses training phase

* remove unnecessary phase setting in training worker

* reorganize rollout worker

* provide default name to GlobalVariableSaver.__init__ since it isn't really used anyway

* allow dividing TrainingSteps and EnvironmentSteps

* add timestamps to the log

* added redis data store

* conflict merge fix

rl_coach/data_stores/checkpoint_data_store.py

@@ -0,0 +1,96 @@
+#
+# Copyright (c) 2017 Intel Corporation
+#
+# 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.
+#
+import time
+import os
+
+from rl_coach.checkpoint import CheckpointStateReader
+from rl_coach.data_stores.data_store import SyncFiles
+
+
+class CheckpointDataStore(object):
+    """
+    A DataStore which relies on the GraphManager check pointing methods to communicate policies.
+    """
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.checkpoint_num = 0
+
+    def end_of_policies(self) -> bool:
+        """
+        Returns true if no new policies will be added to this DataStore. This typically happens
+        because training has completed and is used to signal to the rollout workers to stop.
+        """
+        return os.path.exists(
+            os.path.join(self.checkpoint_dir, SyncFiles.FINISHED.value)
+        )
+
+    def save_policy(self, graph_manager):
+        # TODO: it would be nice if restore_checkpoint accepted a checkpoint path as a
+        # parameter. as it is, one cannot distinguish between checkpoints used for coordination
+        # and checkpoints requested to a persistent disk for later use
+        graph_manager.task_parameters.checkpoint_restore_path = self.checkpoint_dir
+        graph_manager.save_checkpoint()
+
+    def load_policy(self, graph_manager, require_new_policy=True, timeout=None):
+        """
+        Load a checkpoint into the specified graph_manager. The expectation here is that
+        save_to_store() and load_from_store() will synchronize a checkpoint directory with a
+        central repository such as NFS or S3.
+
+        :param graph_manager: the graph_manager to load the policy into
+        :param require_new_policy: if True, only load a policy if it hasn't been loaded in this
+        process yet before.
+        :param timeout: Will only try to load the policy once if timeout is None, otherwise will
+        retry for timeout seconds
+        """
+        if self._new_policy_exists(require_new_policy, timeout):
+            # TODO: it would be nice if restore_checkpoint accepted a checkpoint path as a
+            # parameter. as it is, one cannot distinguish between checkpoints used for coordination
+            # and checkpoints requested to a persistent disk for later use
+            graph_manager.task_parameters.checkpoint_restore_path = self.checkpoint_dir
+            graph_manager.restore_checkpoint()
+
+    def _new_policy_exists(self, require_new_policy=True, timeout=None) -> bool:
+        """
+        :param require_new_policy: if True, only load a policy if it hasn't been loaded in this
+        process yet before.
+        :param timeout: Will only try to load the policy once if timeout is None, otherwise will
+        retry for timeout seconds
+        """
+        checkpoint_state_reader = CheckpointStateReader(
+            self.checkpoint_dir, checkpoint_state_optional=False
+        )
+        checkpoint = "first"
+        if timeout is None:
+            timeout = 0
+        timeout_ends = time.time() + timeout
+        while time.time() < timeout_ends or checkpoint == "first":
+            if self.end_of_policies():
+                return False
+
+            self.load_from_store()
+
+            checkpoint = checkpoint_state_reader.get_latest()
+            if checkpoint is not None:
+                if not require_new_policy or checkpoint.num > self.checkpoint_num:
+                    self.checkpoint_num = checkpoint.num
+                    return True
+
+        raise ValueError(
+            "Waited for {timeout} seconds, but no first policy was received.".format(
+                timeout=timeout
+            )
+        )