| # Copyright 2015, Google Inc. |
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| # |
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| |
| """The base interface of RPC Framework. |
| |
| Implementations of this interface support the conduct of "operations": |
| exchanges between two distinct ends of an arbitrary number of data payloads |
| and metadata such as a name for the operation, initial and terminal metadata |
| in each direction, and flow control. These operations may be used for transfers |
| of data, remote procedure calls, status indication, or anything else |
| applications choose. |
| """ |
| |
| # threading is referenced from specification in this module. |
| import abc |
| import enum |
| import threading |
| |
| # abandonment is referenced from specification in this module. |
| from grpc.framework.foundation import abandonment # pylint: disable=unused-import |
| |
| |
| class NoSuchMethodError(Exception): |
| """Indicates that an unrecognized operation has been called.""" |
| |
| |
| @enum.unique |
| class Outcome(enum.Enum): |
| """Operation outcomes.""" |
| |
| COMPLETED = 'completed' |
| CANCELLED = 'cancelled' |
| EXPIRED = 'expired' |
| LOCAL_SHUTDOWN = 'local shutdown' |
| REMOTE_SHUTDOWN = 'remote shutdown' |
| RECEPTION_FAILURE = 'reception failure' |
| TRANSMISSION_FAILURE = 'transmission failure' |
| LOCAL_FAILURE = 'local failure' |
| REMOTE_FAILURE = 'remote failure' |
| |
| |
| class Completion(object): |
| """An aggregate of the values exchanged upon operation completion. |
| |
| Attributes: |
| terminal_metadata: A terminal metadata value for the operaton. |
| code: A code value for the operation. |
| message: A message value for the operation. |
| """ |
| __metaclass__ = abc.ABCMeta |
| |
| |
| class OperationContext(object): |
| """Provides operation-related information and action.""" |
| __metaclass__ = abc.ABCMeta |
| |
| @abc.abstractmethod |
| def outcome(self): |
| """Indicates the operation's outcome (or that the operation is ongoing). |
| |
| Returns: |
| None if the operation is still active or the Outcome value for the |
| operation if it has terminated. |
| """ |
| raise NotImplementedError() |
| |
| @abc.abstractmethod |
| def add_termination_callback(self, callback): |
| """Adds a function to be called upon operation termination. |
| |
| Args: |
| callback: A callable to be passed an Outcome value on operation |
| termination. |
| |
| Returns: |
| None if the operation has not yet terminated and the passed callback will |
| later be called when it does terminate, or if the operation has already |
| terminated an Outcome value describing the operation termination and the |
| passed callback will not be called as a result of this method call. |
| """ |
| raise NotImplementedError() |
| |
| @abc.abstractmethod |
| def time_remaining(self): |
| """Describes the length of allowed time remaining for the operation. |
| |
| Returns: |
| A nonnegative float indicating the length of allowed time in seconds |
| remaining for the operation to complete before it is considered to have |
| timed out. Zero is returned if the operation has terminated. |
| """ |
| raise NotImplementedError() |
| |
| @abc.abstractmethod |
| def cancel(self): |
| """Cancels the operation if the operation has not yet terminated.""" |
| raise NotImplementedError() |
| |
| @abc.abstractmethod |
| def fail(self, exception): |
| """Indicates that the operation has failed. |
| |
| Args: |
| exception: An exception germane to the operation failure. May be None. |
| """ |
| raise NotImplementedError() |
| |
| |
| class Operator(object): |
| """An interface through which to participate in an operation.""" |
| __metaclass__ = abc.ABCMeta |
| |
| @abc.abstractmethod |
| def advance( |
| self, initial_metadata=None, payload=None, completion=None, |
| allowance=None): |
| """Progresses the operation. |
| |
| Args: |
| initial_metadata: An initial metadata value. Only one may ever be |
| communicated in each direction for an operation, and they must be |
| communicated no later than either the first payload or the completion. |
| payload: A payload value. |
| completion: A Completion value. May only ever be non-None once in either |
| direction, and no payloads may be passed after it has been communicated. |
| allowance: A positive integer communicating the number of additional |
| payloads allowed to be passed by the remote side of the operation. |
| """ |
| raise NotImplementedError() |
| |
| |
| class Subscription(object): |
| """Describes customer code's interest in values from the other side. |
| |
| Attributes: |
| kind: A Kind value describing the overall kind of this value. |
| termination_callback: A callable to be passed the Outcome associated with |
| the operation after it has terminated. Must be non-None if kind is |
| Kind.TERMINATION_ONLY. Must be None otherwise. |
| allowance: A callable behavior that accepts positive integers representing |
| the number of additional payloads allowed to be passed to the other side |
| of the operation. Must be None if kind is Kind.FULL. Must not be None |
| otherwise. |
| operator: An Operator to be passed values from the other side of the |
| operation. Must be non-None if kind is Kind.FULL. Must be None otherwise. |
| """ |
| |
| @enum.unique |
| class Kind(enum.Enum): |
| |
| NONE = 'none' |
| TERMINATION_ONLY = 'termination only' |
| FULL = 'full' |
| |
| |
| class Servicer(object): |
| """Interface for service implementations.""" |
| __metaclass__ = abc.ABCMeta |
| |
| @abc.abstractmethod |
| def service(self, group, method, context, output_operator): |
| """Services an operation. |
| |
| Args: |
| group: The group identifier of the operation to be serviced. |
| method: The method identifier of the operation to be serviced. |
| context: An OperationContext object affording contextual information and |
| actions. |
| output_operator: An Operator that will accept output values of the |
| operation. |
| |
| Returns: |
| A Subscription via which this object may or may not accept more values of |
| the operation. |
| |
| Raises: |
| NoSuchMethodError: If this Servicer does not handle operations with the |
| given group and method. |
| abandonment.Abandoned: If the operation has been aborted and there no |
| longer is any reason to service the operation. |
| """ |
| raise NotImplementedError() |
| |
| |
| class End(object): |
| """Common type for entry-point objects on both sides of an operation.""" |
| __metaclass__ = abc.ABCMeta |
| |
| @abc.abstractmethod |
| def start(self): |
| """Starts this object's service of operations.""" |
| raise NotImplementedError() |
| |
| @abc.abstractmethod |
| def stop(self, grace): |
| """Stops this object's service of operations. |
| |
| This object will refuse service of new operations as soon as this method is |
| called but operations under way at the time of the call may be given a |
| grace period during which they are allowed to finish. |
| |
| Args: |
| grace: A duration of time in seconds to allow ongoing operations to |
| terminate before being forcefully terminated by the stopping of this |
| End. May be zero to terminate all ongoing operations and immediately |
| stop. |
| |
| Returns: |
| A threading.Event that will be set to indicate all operations having |
| terminated and this End having completely stopped. The returned event |
| may not be set until after the full grace period (if some ongoing |
| operation continues for the full length of the period) or it may be set |
| much sooner (if for example this End had no operations in progress at |
| the time its stop method was called). |
| """ |
| raise NotImplementedError() |
| |
| @abc.abstractmethod |
| def operate( |
| self, group, method, subscription, timeout, initial_metadata=None, |
| payload=None, completion=None): |
| """Commences an operation. |
| |
| Args: |
| group: The group identifier of the invoked operation. |
| method: The method identifier of the invoked operation. |
| subscription: A Subscription to which the results of the operation will be |
| passed. |
| timeout: A length of time in seconds to allow for the operation. |
| initial_metadata: An initial metadata value to be sent to the other side |
| of the operation. May be None if the initial metadata will be later |
| passed via the returned operator or if there will be no initial metadata |
| passed at all. |
| payload: An initial payload for the operation. |
| completion: A Completion value indicating the end of transmission to the |
| other side of the operation. |
| |
| Returns: |
| A pair of objects affording information about the operation and action |
| continuing the operation. The first element of the returned pair is an |
| OperationContext for the operation and the second element of the |
| returned pair is an Operator to which operation values not passed in |
| this call should later be passed. |
| """ |
| raise NotImplementedError() |
| |
| @abc.abstractmethod |
| def operation_stats(self): |
| """Reports the number of terminated operations broken down by outcome. |
| |
| Returns: |
| A dictionary from Outcome value to an integer identifying the number |
| of operations that terminated with that outcome. |
| """ |
| raise NotImplementedError() |
| |
| @abc.abstractmethod |
| def add_idle_action(self, action): |
| """Adds an action to be called when this End has no ongoing operations. |
| |
| Args: |
| action: A callable that accepts no arguments. |
| """ |
| raise NotImplementedError() |