When we set the call state to "CANCELLED" after
grpc_cancel_all_calls, we would block other start batch
operations from happening. The rpc_state for the cancelled
call would still be in the server's rpc_states set, but it
would never get removed because there were no active batches
for the call, and the only place we remove from rpc_states is
when a batch completes.
It is better to rely on c-core's cancellation. Once a call
is cancelled, all subsequent ops on that call will return
immediately with a cancellation error.
The RLock() change is due to the possibility that
_on_call_completed
gets invoked immediately when the call has already completed when the
rpc_future callback is created.
gRPC Python required RPCs terminating with non-OK status code to still
return a valid response value after calling set_code, even though the
response value was not supposed to be communicated to the client, and
returning None is considered a programming error.
This commit introduces an alternative mechanism to terminate RPCs by
calling the `abort` method on `ServicerContext` passed to the handler,
which raises an exception and signals to the gRPC runtime to abort the
RPC with the specified status code and details.
A GenericRpcHandler registered on a gRPC Server is not supposed to raise
an exception and if it does so it is considered a programming defect.
However, gRPC is supposed to respond to the client with an UNKNOWN
status code. Previously, this situation was left unhandled and the
client ended up receiving a response with CANCELLED status code.
This commit fixes the issue https://github.com/grpc/grpc/issues/13629.
Rather than allocating gRPC Core memory when instantiated and
retaining it until deleted, gRPC Python's credentials objects now
offer methods to create gRPC Core structures on demand.
"Do not make undocumented and unsupported use of one part of an API
from within the implementation of another part of the same API" is one
of the rules of Abstraction Club. Not sure if it's important enough to
be the first two rules, but it's up there.
Mehrdad Afshari