Beta API clean-ups

(1) Renamed the "beta" module "implementations" because it hasn't been
monolithic since "interfaces" was factored out of it a few changes
back.

(2) Moved ChannelConnectivity from grpc.beta.beta to
grpc.beta.interfaces since it is constants that don't depend on the
beta implementation.

(3) Moved the Server interface definition from grpc.beta.beta to
grpc.beta.interfaces since it is an interface.

(4) Dropped the "create_" prefix from "create_<...>_channel" functions
to better match the other creation functions throughout the codebase.

5 files changed, 138 insertions, 149 deletions

diff --git a/src/python/grpcio/grpc/beta/_connectivity_channel.py b/src/python/grpcio/grpc/beta/_connectivity_channel.py
index 457ede79f2..61674a70ad 100644
--- a/src/python/grpcio/grpc/beta/_connectivity_channel.py
+++ b/src/python/grpcio/grpc/beta/_connectivity_channel.py
@@ -33,18 +33,24 @@ import threading
 import time
 
 from grpc._adapter import _low
+from grpc._adapter import _types
+from grpc.beta import interfaces
 from grpc.framework.foundation import callable_util
 
 _CHANNEL_SUBSCRIPTION_CALLBACK_ERROR_LOG_MESSAGE = (
     'Exception calling channel subscription callback!')
 
+_LOW_CONNECTIVITY_STATE_TO_CHANNEL_CONNECTIVITY = {
+    state: connectivity for state, connectivity in zip(
+        _types.ConnectivityState, interfaces.ChannelConnectivity)
+}
+
 
 class ConnectivityChannel(object):
 
-  def __init__(self, low_channel, mapping):
+  def __init__(self, low_channel):
     self._lock = threading.Lock()
     self._low_channel = low_channel
-    self._mapping = mapping
 
     self._polling = False
     self._connectivity = None
@@ -88,7 +94,8 @@ class ConnectivityChannel(object):
     try_to_connect = initial_try_to_connect
     low_connectivity = low_channel.check_connectivity_state(try_to_connect)
     with self._lock:
-      self._connectivity = self._mapping[low_connectivity]
+      self._connectivity = _LOW_CONNECTIVITY_STATE_TO_CHANNEL_CONNECTIVITY[
+          low_connectivity]
       callbacks = tuple(
           callback for callback, unused_but_known_to_be_none_connectivity
           in self._callbacks_and_connectivities)
@@ -112,7 +119,8 @@ class ConnectivityChannel(object):
       if event.success or try_to_connect:
         low_connectivity = low_channel.check_connectivity_state(try_to_connect)
         with self._lock:
-          self._connectivity = self._mapping[low_connectivity]
+          self._connectivity = _LOW_CONNECTIVITY_STATE_TO_CHANNEL_CONNECTIVITY[
+              low_connectivity]
           if not self._delivering:
             callbacks = self._deliveries(self._connectivity)
             if callbacks:
diff --git a/src/python/grpcio/grpc/beta/_server.py b/src/python/grpcio/grpc/beta/_server.py
index ebf91d80ab..daa42c475a 100644
--- a/src/python/grpcio/grpc/beta/_server.py
+++ b/src/python/grpcio/grpc/beta/_server.py
@@ -72,7 +72,7 @@ def _disassemble(grpc_link, end_link, pool, event, grace):
   event.set()
 
 
-class Server(object):
+class Server(interfaces.Server):
 
   def __init__(self, grpc_link, end_link, pool):
     self._grpc_link = grpc_link
@@ -82,9 +82,9 @@ class Server(object):
   def add_insecure_port(self, address):
     return self._grpc_link.add_port(address, None)
 
-  def add_secure_port(self, address, intermediary_low_server_credentials):
+  def add_secure_port(self, address, server_credentials):
     return self._grpc_link.add_port(
-        address, intermediary_low_server_credentials)
+        address, server_credentials._intermediary_low_credentials)  # pylint: disable=protected-access
 
   def start(self):
     self._grpc_link.join_link(self._end_link)
diff --git a/src/python/grpcio/grpc/beta/beta.py b/src/python/grpcio/grpc/beta/implementations.py
index b3a161087f..9b461fb3dd 100644
--- a/src/python/grpcio/grpc/beta/beta.py
+++ b/src/python/grpcio/grpc/beta/implementations.py
@@ -40,6 +40,7 @@ from grpc._adapter import _types
 from grpc.beta import _connectivity_channel
 from grpc.beta import _server
 from grpc.beta import _stub
+from grpc.beta import interfaces
 from grpc.framework.common import cardinality  # pylint: disable=unused-import
 from grpc.framework.interfaces.face import face  # pylint: disable=unused-import
 
@@ -47,32 +48,6 @@ _CHANNEL_SUBSCRIPTION_CALLBACK_ERROR_LOG_MESSAGE = (
     'Exception calling channel subscription callback!')
 
 
-@enum.unique
-class ChannelConnectivity(enum.Enum):
-  """Mirrors grpc_connectivity_state in the gRPC Core.
-
-  Attributes:
-    IDLE: The channel is idle.
-    CONNECTING: The channel is connecting.
-    READY: The channel is ready to conduct RPCs.
-    TRANSIENT_FAILURE: The channel has seen a failure from which it expects to
-      recover.
-    FATAL_FAILURE: The channel has seen a failure from which it cannot recover.
-  """
-
-  IDLE = (_types.ConnectivityState.IDLE, 'idle',)
-  CONNECTING = (_types.ConnectivityState.CONNECTING, 'connecting',)
-  READY = (_types.ConnectivityState.READY, 'ready',)
-  TRANSIENT_FAILURE = (
-      _types.ConnectivityState.TRANSIENT_FAILURE, 'transient failure',)
-  FATAL_FAILURE = (_types.ConnectivityState.FATAL_FAILURE, 'fatal failure',)
-
-_LOW_CONNECTIVITY_STATE_TO_CHANNEL_CONNECTIVITY = {
-    state: connectivity for state, connectivity in zip(
-        _types.ConnectivityState, ChannelConnectivity)
-}
-
-
 class ClientCredentials(object):
   """A value encapsulating the data required to create a secure Channel.
 
@@ -118,13 +93,14 @@ class Channel(object):
     self._low_channel = low_channel
     self._intermediary_low_channel = intermediary_low_channel
     self._connectivity_channel = _connectivity_channel.ConnectivityChannel(
-        low_channel, _LOW_CONNECTIVITY_STATE_TO_CHANNEL_CONNECTIVITY)
+        low_channel)
 
   def subscribe(self, callback, try_to_connect=None):
     """Subscribes to this Channel's connectivity.
 
     Args:
-      callback: A callable to be invoked and passed this Channel's connectivity.
+      callback: A callable to be invoked and passed an
+        interfaces.ChannelConnectivity identifying this Channel's connectivity.
         The callable will be invoked immediately upon subscription and again for
         every change to this Channel's connectivity thereafter until it is
         unsubscribed.
@@ -144,7 +120,7 @@ class Channel(object):
     self._connectivity_channel.unsubscribe(callback)
 
 
-def create_insecure_channel(host, port):
+def insecure_channel(host, port):
   """Creates an insecure Channel to a remote host.
 
   Args:
@@ -159,7 +135,7 @@ def create_insecure_channel(host, port):
   return Channel(intermediary_low_channel._internal, intermediary_low_channel)  # pylint: disable=protected-access
 
 
-def create_secure_channel(host, port, client_credentials):
+def secure_channel(host, port, client_credentials):
   """Creates a secure Channel to a remote host.
 
   Args:
@@ -313,86 +289,6 @@ def ssl_server_credentials(
         intermediary_low_credentials._internal, intermediary_low_credentials)  # pylint: disable=protected-access
 
 
-class Server(object):
-  """Services RPCs."""
-  __metaclass__ = abc.ABCMeta
-
-  @abc.abstractmethod
-  def add_insecure_port(self, address):
-    """Reserves a port for insecure RPC service once this Server becomes active.
-
-    This method may only be called before calling this Server's start method is
-    called.
-
-    Args:
-      address: The address for which to open a port.
-
-    Returns:
-      An integer port on which RPCs will be serviced after this link has been
-        started. This is typically the same number as the port number contained
-        in the passed address, but will likely be different if the port number
-        contained in the passed address was zero.
-    """
-    raise NotImplementedError()
-
-  @abc.abstractmethod
-  def add_secure_port(self, address, server_credentials):
-    """Reserves a port for secure RPC service after this Server becomes active.
-
-    This method may only be called before calling this Server's start method is
-    called.
-
-    Args:
-      address: The address for which to open a port.
-      server_credentials: A ServerCredentials.
-
-    Returns:
-      An integer port on which RPCs will be serviced after this link has been
-        started. This is typically the same number as the port number contained
-        in the passed address, but will likely be different if the port number
-        contained in the passed address was zero.
-    """
-    raise NotImplementedError()
-
-  @abc.abstractmethod
-  def start(self):
-    """Starts this Server's service of RPCs.
-
-    This method may only be called while the server is not serving RPCs (i.e. it
-    is not idempotent).
-    """
-    raise NotImplementedError()
-
-  @abc.abstractmethod
-  def stop(self, grace):
-    """Stops this Server's service of RPCs.
-
-    All calls to this method immediately stop service of new RPCs. When existing
-    RPCs are aborted is controlled by the grace period parameter passed to this
-    method.
-
-    This method may be called at any time and is idempotent. Passing a smaller
-    grace value than has been passed in a previous call will have the effect of
-    stopping the Server sooner. Passing a larger grace value than has been
-    passed in a previous call will not have the effect of stopping the sooner
-    later.
-
-    Args:
-      grace: A duration of time in seconds to allow existing RPCs to complete
-        before being aborted by this Server's stopping. May be zero for
-        immediate abortion of all in-progress RPCs.
-
-    Returns:
-      A threading.Event that will be set when this Server has completely
-      stopped. The returned event may not be set until after the full grace
-      period (if some ongoing RPC continues for the full length of the period)
-      of it may be set much sooner (such as if this Server had no RPCs underway
-      at the time it was stopped or if all RPCs that it had underway completed
-      very early in the grace period).
-    """
-    raise NotImplementedError()
-
-
 class ServerOptions(object):
   """A value encapsulating the various options for creation of a Server.
 
@@ -450,27 +346,8 @@ def server_options(
       thread_pool, thread_pool_size, default_timeout, maximum_timeout)
 
 
-class _Server(Server):
-
-  def __init__(self, underserver):
-    self._underserver = underserver
-
-  def add_insecure_port(self, address):
-    return self._underserver.add_insecure_port(address)
-
-  def add_secure_port(self, address, server_credentials):
-    return self._underserver.add_secure_port(
-        address, server_credentials._intermediary_low_credentials)  # pylint: disable=protected-access
-
-  def start(self):
-    self._underserver.start()
-
-  def stop(self, grace):
-    return self._underserver.stop(grace)
-
-
 def server(service_implementations, options=None):
-  """Creates a Server with which RPCs can be serviced.
+  """Creates an interfaces.Server with which RPCs can be serviced.
 
   Args:
     service_implementations: A dictionary from service name-method name pair to
@@ -479,13 +356,12 @@ def server(service_implementations, options=None):
       functionality of the returned Server.
 
   Returns:
-    A Server with which RPCs can be serviced.
+    An interfaces.Server with which RPCs can be serviced.
   """
   effective_options = _EMPTY_SERVER_OPTIONS if options is None else options
-  underserver = _server.server(
+  return _server.server(
       service_implementations, effective_options.multi_method_implementation,
       effective_options.request_deserializers,
       effective_options.response_serializers, effective_options.thread_pool,
       effective_options.thread_pool_size, effective_options.default_timeout,
       effective_options.maximum_timeout)
-  return _Server(underserver)
diff --git a/src/python/grpcio/grpc/beta/interfaces.py b/src/python/grpcio/grpc/beta/interfaces.py
index 79f2620dd4..07c8618f70 100644
--- a/src/python/grpcio/grpc/beta/interfaces.py
+++ b/src/python/grpcio/grpc/beta/interfaces.py
@@ -32,6 +32,28 @@
 import abc
 import enum
 
+from grpc._adapter import _types
+
+
+@enum.unique
+class ChannelConnectivity(enum.Enum):
+  """Mirrors grpc_connectivity_state in the gRPC Core.
+
+  Attributes:
+    IDLE: The channel is idle.
+    CONNECTING: The channel is connecting.
+    READY: The channel is ready to conduct RPCs.
+    TRANSIENT_FAILURE: The channel has seen a failure from which it expects to
+      recover.
+    FATAL_FAILURE: The channel has seen a failure from which it cannot recover.
+  """
+  IDLE = (_types.ConnectivityState.IDLE, 'idle',)
+  CONNECTING = (_types.ConnectivityState.CONNECTING, 'connecting',)
+  READY = (_types.ConnectivityState.READY, 'ready',)
+  TRANSIENT_FAILURE = (
+      _types.ConnectivityState.TRANSIENT_FAILURE, 'transient failure',)
+  FATAL_FAILURE = (_types.ConnectivityState.FATAL_FAILURE, 'fatal failure',)
+
 
 @enum.unique
 class StatusCode(enum.Enum):
@@ -110,3 +132,83 @@ class GRPCInvocationContext(object):
   def disable_next_request_compression(self):
     """Disables compression of the next request passed by the application."""
     raise NotImplementedError()
+
+
+class Server(object):
+  """Services RPCs."""
+  __metaclass__ = abc.ABCMeta
+
+  @abc.abstractmethod
+  def add_insecure_port(self, address):
+    """Reserves a port for insecure RPC service once this Server becomes active.
+
+    This method may only be called before calling this Server's start method is
+    called.
+
+    Args:
+      address: The address for which to open a port.
+
+    Returns:
+      An integer port on which RPCs will be serviced after this link has been
+        started. This is typically the same number as the port number contained
+        in the passed address, but will likely be different if the port number
+        contained in the passed address was zero.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def add_secure_port(self, address, server_credentials):
+    """Reserves a port for secure RPC service after this Server becomes active.
+
+    This method may only be called before calling this Server's start method is
+    called.
+
+    Args:
+      address: The address for which to open a port.
+      server_credentials: A ServerCredentials.
+
+    Returns:
+      An integer port on which RPCs will be serviced after this link has been
+        started. This is typically the same number as the port number contained
+        in the passed address, but will likely be different if the port number
+        contained in the passed address was zero.
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def start(self):
+    """Starts this Server's service of RPCs.
+
+    This method may only be called while the server is not serving RPCs (i.e. it
+    is not idempotent).
+    """
+    raise NotImplementedError()
+
+  @abc.abstractmethod
+  def stop(self, grace):
+    """Stops this Server's service of RPCs.
+
+    All calls to this method immediately stop service of new RPCs. When existing
+    RPCs are aborted is controlled by the grace period parameter passed to this
+    method.
+
+    This method may be called at any time and is idempotent. Passing a smaller
+    grace value than has been passed in a previous call will have the effect of
+    stopping the Server sooner. Passing a larger grace value than has been
+    passed in a previous call will not have the effect of stopping the sooner
+    later.
+
+    Args:
+      grace: A duration of time in seconds to allow existing RPCs to complete
+        before being aborted by this Server's stopping. May be zero for
+        immediate abortion of all in-progress RPCs.
+
+    Returns:
+      A threading.Event that will be set when this Server has completely
+      stopped. The returned event may not be set until after the full grace
+      period (if some ongoing RPC continues for the full length of the period)
+      of it may be set much sooner (such as if this Server had no RPCs underway
+      at the time it was stopped or if all RPCs that it had underway completed
+      very early in the grace period).
+    """
+    raise NotImplementedError()
diff --git a/src/python/grpcio/grpc/beta/utilities.py b/src/python/grpcio/grpc/beta/utilities.py
index 1b5356e3ad..fb07a76579 100644
--- a/src/python/grpcio/grpc/beta/utilities.py
+++ b/src/python/grpcio/grpc/beta/utilities.py
@@ -32,7 +32,9 @@
 import threading
 import time
 
-from grpc.beta import beta
+# implementations is referenced from specification in this module.
+from grpc.beta import implementations  # pylint: disable=unused-import
+from grpc.beta import interfaces
 from grpc.framework.foundation import callable_util
 from grpc.framework.foundation import future
 
@@ -70,7 +72,8 @@ class _ChannelReadyFuture(future.Future):
 
   def _update(self, connectivity):
     with self._condition:
-      if not self._cancelled and connectivity is beta.ChannelConnectivity.READY:
+      if (not self._cancelled and
+          connectivity is interfaces.ChannelConnectivity.READY):
         self._matured = True
         self._channel.unsubscribe(self._update)
         self._condition.notify_all()
@@ -141,19 +144,19 @@ class _ChannelReadyFuture(future.Future):
 
 
 def channel_ready_future(channel):
-  """Creates a future.Future that matures when a beta.Channel is ready.
+  """Creates a future.Future tracking when an implementations.Channel is ready.
 
-  Cancelling the returned future.Future does not tell the given beta.Channel to
-  abandon attempts it may have been making to connect; cancelling merely
-  deactivates the return future.Future's subscription to the given
-  beta.Channel's connectivity.
+  Cancelling the returned future.Future does not tell the given
+  implementations.Channel to abandon attempts it may have been making to
+  connect; cancelling merely deactivates the return future.Future's
+  subscription to the given implementations.Channel's connectivity.
 
   Args:
-    channel: A beta.Channel.
+    channel: An implementations.Channel.
 
   Returns:
     A future.Future that matures when the given Channel has connectivity
-      beta.ChannelConnectivity.READY.
+      interfaces.ChannelConnectivity.READY.
   """
   ready_future = _ChannelReadyFuture(channel)
   ready_future.start()