Implement frame-work agnostic rollout and training workers (#137)

* Added checkpoint state file to coach checkpointing.

* Removed TF specific code from rollout_worker, training_worker, and s3_data_store

rl_coach/utils.py

@@ -546,58 +546,3 @@ def start_shell_command_and_wait(command):
 
 def indent_string(string):
     return '\t' + string.replace('\n', '\n\t')
-
-
-class CheckpointState(object):
-    """
-    Helper class for checkpoint directory information. It replicates
-    the CheckpointState protobuf class in tensorflow.
-    """
-    def __init__(self, checkpoints: List[str]):
-        self._checkpoints = checkpoints
-
-    @property
-    def all_model_checkpoint_paths(self):
-        return self._checkpoints
-
-    @property
-    def model_checkpoint_path(self):
-        return self._checkpoints[-1]
-
-    def __str__(self):
-        out_str = 'model_checkpoint_path: {}\n'.format(self.model_checkpoint_path)
-        for c in self._checkpoints:
-            out_str += 'all_model_checkpoint_paths: {}\n'.format(c)
-        return out_str
-
-    def __repr__(self):
-        return str(self._checkpoints)
-
-
-COACH_CHECKPOINT_PATTERN = r'\A(([0-9]+)[^0-9])?.*?\.ckpt(-([0-9]+))?'
-
-
-def get_checkpoint_state(checkpoint_dir: Union[str, List[str]], filename_pattern: str=COACH_CHECKPOINT_PATTERN) ->\
-        Union[CheckpointState, None]:
-    """
-    Finds the latest checkpoint file. It uses the first group of filename_pattern (i.e. group(2) or group(4) to sort
-    the checkpoint names and find the latest checkpoint
-    :param checkpoint_dir: directory where checkpoints are saved or list of all files in a directory
-    :param filename_pattern: regex pattern for checkpoint filenames
-    :return: a CheckpointState for checkpoint_dir containing a sorted list of checkpoint names. If no matching
-        files are found, returns None.
-    """
-    prog = re.compile(filename_pattern)
-    checkpoints = dict()
-    filenames = os.listdir(checkpoint_dir) if isinstance(checkpoint_dir, str) else checkpoint_dir
-    for name in filenames:
-        m = prog.search(name)
-        if m is not None and (m.group(2) is not None or m.group(4) is not None):
-            if m.group(2) is not None and m.group(4) is not None:
-                assert m.group(2) == m.group(4)
-            checkpoint_count = int(m.group(2) if m.group(2) is not None else m.group(4))
-            full_path = os.path.join(checkpoint_dir, m.group(0)) if isinstance(checkpoint_dir, str) else m.group(0)
-            checkpoints[checkpoint_count] = full_path
-    if len(checkpoints) == 0:
-        return None
-    return CheckpointState([checkpoints[k] for k in sorted(checkpoints.keys())])