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#!/usr/bin/env python
#
# Copyright 2007 Google Inc.
#
# 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.
#
"""Container of APIProxy stubs for more convenient unittesting.
Classes/variables/functions defined here:
APIProxyStubMap: container of APIProxy stubs.
apiproxy: global instance of an APIProxyStubMap.
MakeSyncCall: APIProxy entry point.
UserRPC: User-visible class wrapping asynchronous RPCs.
"""
import inspect
import sys
import threading
from google.appengine.api import apiproxy_rpc
from google.appengine.runtime import apiproxy_errors
def CreateRPC(service, stubmap=None):
"""Creates a RPC instance for the given service.
The instance is suitable for talking to remote services.
Each RPC instance can be used only once, and should not be reused.
Args:
service: string representing which service to call.
stubmap: optional APIProxyStubMap instance, for dependency injection.
Returns:
the rpc object.
Raises:
AssertionError or RuntimeError if the stub for service doesn't supply a
CreateRPC method.
"""
if stubmap is None:
stubmap = apiproxy
stub = stubmap.GetStub(service)
assert stub, 'No api proxy found for service "%s"' % service
assert hasattr(stub, 'CreateRPC'), (('The service "%s" doesn\'t have ' +
'a CreateRPC method.') % service)
return stub.CreateRPC()
def MakeSyncCall(service, call, request, response, stubmap=None):
"""The APIProxy entry point for a synchronous API call.
Args:
service: string representing which service to call
call: string representing which function to call
request: protocol buffer for the request
response: protocol buffer for the response
stubmap: optional APIProxyStubMap instance, for dependency injection.
Returns:
Response protocol buffer or None. Some implementations may return
a response protocol buffer instead of modifying 'response'.
Caller must use returned value in such cases. If 'response' is modified
then returns None.
Raises:
apiproxy_errors.Error or a subclass.
"""
if stubmap is None:
stubmap = apiproxy
return stubmap.MakeSyncCall(service, call, request, response)
class ListOfHooks(object):
"""An ordered collection of hooks for a particular API call.
A hook is a function that has exactly the same signature as
a service stub. It will be called before or after an api hook is
executed, depending on whether this list is for precall of postcall hooks.
Hooks can be used for debugging purposes (check certain
pre- or postconditions on api calls) or to apply patches to protocol
buffers before/after a call gets submitted.
"""
def __init__(self):
"""Constructor."""
self.__content = []
self.__unique_keys = set()
def __len__(self):
"""Returns the amount of elements in the collection."""
return self.__content.__len__()
def __Insert(self, index, key, function, service=None):
"""Appends a hook at a certain position in the list.
Args:
index: the index of where to insert the function
key: a unique key (within the module) for this particular function.
If something from the same module with the same key is already
registered, nothing will be added.
function: the hook to be added.
service: optional argument that restricts the hook to a particular api
Returns:
True if the collection was modified.
"""
unique_key = (key, inspect.getmodule(function))
if unique_key in self.__unique_keys:
return False
num_args = len(inspect.getargspec(function)[0])
if (inspect.ismethod(function)):
num_args -= 1
self.__content.insert(index, (key, function, service, num_args))
self.__unique_keys.add(unique_key)
return True
def Append(self, key, function, service=None):
"""Appends a hook at the end of the list.
Args:
key: a unique key (within the module) for this particular function.
If something from the same module with the same key is already
registered, nothing will be added.
function: the hook to be added.
service: optional argument that restricts the hook to a particular api
Returns:
True if the collection was modified.
"""
return self.__Insert(len(self), key, function, service)
def Push(self, key, function, service=None):
"""Inserts a hook at the beginning of the list.
Args:
key: a unique key (within the module) for this particular function.
If something from the same module with the same key is already
registered, nothing will be added.
function: the hook to be added.
service: optional argument that restricts the hook to a particular api
Returns:
True if the collection was modified.
"""
return self.__Insert(0, key, function, service)
def Clear(self):
"""Removes all hooks from the list (useful for unit tests)."""
self.__content = []
self.__unique_keys = set()
def Call(self, service, call, request, response, rpc=None, error=None):
"""Invokes all hooks in this collection.
NOTE: For backwards compatibility, if error is not None, hooks
with 4 or 5 arguments are *not* called. This situation
(error=None) only occurs when the RPC request raised an exception;
in the past no hooks would be called at all in that case.
Args:
service: string representing which service to call
call: string representing which function to call
request: protocol buffer for the request
response: protocol buffer for the response
rpc: optional RPC used to make this call
error: optional Exception instance to be passed as 6th argument
"""
for key, function, srv, num_args in self.__content:
if srv is None or srv == service:
if num_args == 6:
function(service, call, request, response, rpc, error)
elif error is not None:
pass
elif num_args == 5:
function(service, call, request, response, rpc)
else:
function(service, call, request, response)
class APIProxyStubMap(object):
"""Container of APIProxy stubs for more convenient unittesting.
Stubs may be either trivial implementations of APIProxy services (e.g.
DatastoreFileStub, UserServiceStub) or "real" implementations.
For unittests, we may want to mix and match real and trivial implementations
of services in order to better focus testing on individual service
implementations. To achieve this, we allow the client to attach stubs to
service names, as well as define a default stub to be used if no specific
matching stub is identified.
"""
def __init__(self, default_stub=None):
"""Constructor.
Args:
default_stub: optional stub
'default_stub' will be used whenever no specific matching stub is found.
"""
self.__stub_map = {}
self.__default_stub = default_stub
self.__precall_hooks = ListOfHooks()
self.__postcall_hooks = ListOfHooks()
def GetPreCallHooks(self):
"""Gets a collection for all precall hooks."""
return self.__precall_hooks
def GetPostCallHooks(self):
"""Gets a collection for all precall hooks."""
return self.__postcall_hooks
def ReplaceStub(self, service, stub):
"""Replace the existing stub for the specified service with a new one.
NOTE: This is a risky operation; external callers should use this with
caution.
Args:
service: string
stub: stub
"""
self.__stub_map[service] = stub
if service == 'datastore':
self.RegisterStub('datastore_v3', stub)
def RegisterStub(self, service, stub):
"""Register the provided stub for the specified service.
Args:
service: string
stub: stub
"""
assert not self.__stub_map.has_key(service), repr(service)
self.ReplaceStub(service, stub)
def GetStub(self, service):
"""Retrieve the stub registered for the specified service.
Args:
service: string
Returns:
stub
Returns the stub registered for 'service', and returns the default stub
if no such stub is found.
"""
return self.__stub_map.get(service, self.__default_stub)
def _CopyStubMap(self):
"""Get a copy of the stub map. For testing only.
Returns:
Get a shallow copy of the stub map.
"""
return dict(self.__stub_map)
def MakeSyncCall(self, service, call, request, response):
"""The APIProxy entry point.
Args:
service: string representing which service to call
call: string representing which function to call
request: protocol buffer for the request
response: protocol buffer for the response
Returns:
Response protocol buffer or None. Some implementations may return
a response protocol buffer instead of modifying 'response'.
Caller must use returned value in such cases. If 'response' is modified
then returns None.
Raises:
apiproxy_errors.Error or a subclass.
"""
stub = self.GetStub(service)
assert stub, 'No api proxy found for service "%s"' % service
if hasattr(stub, 'CreateRPC'):
rpc = stub.CreateRPC()
self.__precall_hooks.Call(service, call, request, response, rpc)
try:
rpc.MakeCall(service, call, request, response)
rpc.Wait()
rpc.CheckSuccess()
except Exception, err:
self.__postcall_hooks.Call(service, call, request, response, rpc, err)
raise
else:
self.__postcall_hooks.Call(service, call, request, response, rpc)
else:
self.__precall_hooks.Call(service, call, request, response)
try:
returned_response = stub.MakeSyncCall(service, call, request, response)
except Exception, err:
self.__postcall_hooks.Call(service, call, request, response, None, err)
raise
else:
self.__postcall_hooks.Call(service, call, request,
returned_response or response)
return returned_response
def CancelApiCalls(self):
if self.__default_stub:
self.__default_stub.CancelApiCalls()
class UserRPC(object):
"""Wrapper class for asynchronous RPC.
Simplest low-level usage pattern:
rpc = UserRPC('service', [deadline], [callback])
rpc.make_call('method', request, response)
.
.
.
rpc.wait()
rpc.check_success()
However, a service module normally provides a wrapper so that the
typical usage pattern becomes more like this:
from google.appengine.api import service
rpc = service.create_rpc([deadline], [callback])
service.make_method_call(rpc, [service-specific-args])
.
.
.
rpc.wait()
result = rpc.get_result()
The service.make_method_call() function sets a service- and method-
specific hook function that is called by rpc.get_result() with the
rpc object as its first argument, and service-specific value as its
second argument. The hook function should call rpc.check_success()
and then extract the user-level result from the rpc.result
protobuffer. Additional arguments may be passed from
make_method_call() to the get_result hook via the second argument.
Also note wait_any() and wait_all(), which wait for multiple RPCs.
"""
__method = None
__get_result_hook = None
__user_data = None
__postcall_hooks_called = False
__must_call_user_callback = False
class MyLocal(threading.local):
"""Class to hold per-thread class level attributes."""
may_interrupt_wait = False
__local = MyLocal()
def __init__(self, service, deadline=None, callback=None, stubmap=None):
"""Constructor.
Args:
service: The service name.
deadline: Optional deadline. Default depends on the implementation.
callback: Optional argument-less callback function.
stubmap: optional APIProxyStubMap instance, for dependency injection.
"""
if stubmap is None:
stubmap = apiproxy
self.__stubmap = stubmap
self.__service = service
self.__rpc = CreateRPC(service, stubmap)
self.__rpc.deadline = deadline
self.__rpc.callback = self.__internal_callback
self.callback = callback
self.__class__.__local.may_interrupt_wait = False
def __internal_callback(self):
"""This is the callback set on the low-level RPC object.
It sets a flag on the current object indicating that the high-level
callback should now be called. If interrupts are enabled, it also
interrupts the current wait_any() call by raising an exception.
"""
self.__must_call_user_callback = True
self.__rpc.callback = None
if self.__class__.__local.may_interrupt_wait and not self.__rpc.exception:
raise apiproxy_errors.InterruptedError(None, self.__rpc)
@property
def service(self):
"""Return the service name."""
return self.__service
@property
def method(self):
"""Return the method name."""
return self.__method
@property
def deadline(self):
"""Return the deadline, if set explicitly (otherwise None)."""
return self.__rpc.deadline
@property
def request(self):
"""Return the request protocol buffer object."""
return self.__rpc.request
@property
def response(self):
"""Return the response protocol buffer object."""
return self.__rpc.response
@property
def state(self):
"""Return the RPC state.
Possible values are attributes of apiproxy_rpc.RPC: IDLE, RUNNING,
FINISHING.
"""
return self.__rpc.state
@property
def get_result_hook(self):
"""Return the get-result hook function."""
return self.__get_result_hook
@property
def user_data(self):
"""Return the user data for the hook function."""
return self.__user_data
def make_call(self, method, request, response,
get_result_hook=None, user_data=None):
"""Initiate a call.
Args:
method: The method name.
request: The request protocol buffer.
response: The response protocol buffer.
get_result_hook: Optional get-result hook function. If not None,
this must be a function with exactly one argument, the RPC
object (self). Its return value is returned from get_result().
user_data: Optional additional arbitrary data for the get-result
hook function. This can be accessed as rpc.user_data. The
type of this value is up to the service module.
This function may only be called once per RPC object. It sends
the request to the remote server, but does not wait for a
response. This allows concurrent execution of the remote call and
further local processing (e.g., making additional remote calls).
Before the call is initiated, the precall hooks are called.
"""
assert self.__rpc.state == apiproxy_rpc.RPC.IDLE, repr(self.state)
self.__method = method
self.__get_result_hook = get_result_hook
self.__user_data = user_data
self.__stubmap.GetPreCallHooks().Call(
self.__service, method, request, response, self.__rpc)
self.__rpc.MakeCall(self.__service, method, request, response)
def wait(self):
"""Wait for the call to complete, and call callback if needed.
This and wait_any()/wait_all() are the only time callback
functions may be called. (However, note that check_success() and
get_result() call wait().) Waiting for one RPC will not cause
callbacks for other RPCs to be called. Callback functions may
call check_success() and get_result().
Callbacks are called without arguments; if a callback needs access
to the RPC object a Python nested function (a.k.a. closure) or a
bound may be used. To facilitate this, the callback may be
assigned after the RPC object is created (but before make_call()
is called).
Note: don't confuse callbacks with get-result hooks or precall
and postcall hooks.
"""
assert self.__rpc.state != apiproxy_rpc.RPC.IDLE, repr(self.state)
if self.__rpc.state == apiproxy_rpc.RPC.RUNNING:
self.__rpc.Wait()
assert self.__rpc.state == apiproxy_rpc.RPC.FINISHING, repr(self.state)
self.__call_user_callback()
def __call_user_callback(self):
"""Call the high-level callback, if requested."""
if self.__must_call_user_callback:
self.__must_call_user_callback = False
if self.callback is not None:
self.callback()
def check_success(self):
"""Check for success of the RPC, possibly raising an exception.
This function should be called at least once per RPC. If wait()
hasn't been called yet, it is called first. If the RPC caused
an exceptional condition, an exception will be raised here.
The first time check_success() is called, the postcall hooks
are called.
"""
self.wait()
try:
self.__rpc.CheckSuccess()
except Exception, err:
if not self.__postcall_hooks_called:
self.__postcall_hooks_called = True
self.__stubmap.GetPostCallHooks().Call(self.__service, self.__method,
self.request, self.response,
self.__rpc, err)
raise
else:
if not self.__postcall_hooks_called:
self.__postcall_hooks_called = True
self.__stubmap.GetPostCallHooks().Call(self.__service, self.__method,
self.request, self.response,
self.__rpc)
def get_result(self):
"""Get the result of the RPC, or possibly raise an exception.
This implies a call to check_success(). If a get-result hook was
passed to make_call(), that hook is responsible for calling
check_success(), and the return value of the hook is returned.
Otherwise, check_success() is called directly and None is
returned.
"""
if self.__get_result_hook is None:
self.check_success()
return None
else:
return self.__get_result_hook(self)
@classmethod
def __check_one(cls, rpcs):
"""Check the list of RPCs for one that is finished, or one that is running.
Args:
rpcs: Iterable collection of UserRPC instances.
Returns:
A pair (finished, running), as follows:
(UserRPC, None) indicating the first RPC found that is finished;
(None, UserRPC) indicating the first RPC found that is running;
(None, None) indicating no RPCs are finished or running.
"""
rpc = None
for rpc in rpcs:
assert isinstance(rpc, cls), repr(rpc)
state = rpc.__rpc.state
if state == apiproxy_rpc.RPC.FINISHING:
rpc.__call_user_callback()
return rpc, None
assert state != apiproxy_rpc.RPC.IDLE, repr(rpc)
return None, rpc
@classmethod
def wait_any(cls, rpcs):
"""Wait until an RPC is finished.
Args:
rpcs: Iterable collection of UserRPC instances.
Returns:
A UserRPC instance, indicating the first RPC among the given
RPCs that finished; or None, indicating that either an RPC not
among the given RPCs finished in the mean time, or the iterable
is empty.
NOTES:
(1) Repeatedly calling wait_any() with the same arguments will not
make progress; it will keep returning the same RPC (the one
that finished first). The callback, however, will only be
called the first time the RPC finishes (which may be here or
in the wait() method).
(2) It may return before any of the given RPCs finishes, if
another pending RPC exists that is not included in the rpcs
argument. In this case the other RPC's callback will *not*
be called. The motivation for this feature is that wait_any()
may be used as a low-level building block for a variety of
high-level constructs, some of which prefer to block for the
minimal amount of time without busy-waiting.
"""
assert iter(rpcs) is not rpcs, 'rpcs must be a collection, not an iterator'
finished, running = cls.__check_one(rpcs)
if finished is not None:
return finished
if running is None:
return None
try:
cls.__local.may_interrupt_wait = True
try:
running.__rpc.Wait()
except apiproxy_errors.InterruptedError, err:
err.rpc._exception = None
err.rpc._traceback = None
finally:
cls.__local.may_interrupt_wait = False
finished, runnning = cls.__check_one(rpcs)
return finished
@classmethod
def wait_all(cls, rpcs):
"""Wait until all given RPCs are finished.
This is a thin wrapper around wait_any() that loops until all
given RPCs have finished.
Args:
rpcs: Iterable collection of UserRPC instances.
Returns:
None.
"""
rpcs = set(rpcs)
while rpcs:
finished = cls.wait_any(rpcs)
if finished is not None:
rpcs.remove(finished)
def GetDefaultAPIProxy():
try:
runtime = __import__('google.appengine.runtime', globals(), locals(),
['apiproxy'])
return APIProxyStubMap(runtime.apiproxy)
except (AttributeError, ImportError):
return APIProxyStubMap()
apiproxy = GetDefaultAPIProxy()