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App Engine Python SDK
v1.6.9 rev.445
The Python runtime is available as an experimental Preview feature.
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Classes | |
class | MyLocal |
Public Member Functions | |
def | __init__ |
def | service |
def | method |
def | deadline |
def | request |
def | response |
def | state |
def | get_result_hook |
def | user_data |
def | make_call |
def | wait |
def | check_success |
def | get_result |
def | wait_any |
def | wait_all |
Public Attributes | |
callback | |
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.
def google.appengine.api.apiproxy_stub_map.UserRPC.__init__ | ( | self, | |
service, | |||
deadline = None , |
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callback = None , |
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stubmap = None |
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) |
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.
def google.appengine.api.apiproxy_stub_map.UserRPC.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.
def google.appengine.api.apiproxy_stub_map.UserRPC.deadline | ( | self | ) |
Return the deadline, if set explicitly (otherwise None).
def google.appengine.api.apiproxy_stub_map.UserRPC.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.
def google.appengine.api.apiproxy_stub_map.UserRPC.get_result_hook | ( | self | ) |
Return the get-result hook function.
def google.appengine.api.apiproxy_stub_map.UserRPC.make_call | ( | self, | |
method, | |||
request, | |||
response, | |||
get_result_hook = None , |
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user_data = None |
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) |
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.
def google.appengine.api.apiproxy_stub_map.UserRPC.method | ( | self | ) |
Return the method name.
def google.appengine.api.apiproxy_stub_map.UserRPC.request | ( | self | ) |
Return the request protocol buffer object.
def google.appengine.api.apiproxy_stub_map.UserRPC.response | ( | self | ) |
Return the response protocol buffer object.
def google.appengine.api.apiproxy_stub_map.UserRPC.service | ( | self | ) |
Return the service name.
def google.appengine.api.apiproxy_stub_map.UserRPC.state | ( | self | ) |
Return the RPC state. Possible values are attributes of apiproxy_rpc.RPC: IDLE, RUNNING, FINISHING.
def google.appengine.api.apiproxy_stub_map.UserRPC.user_data | ( | self | ) |
Return the user data for the hook function.
def google.appengine.api.apiproxy_stub_map.UserRPC.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.
def google.appengine.api.apiproxy_stub_map.UserRPC.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.
def google.appengine.api.apiproxy_stub_map.UserRPC.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.