Support gRPC Python client-side fork with epoll1

A process may fork after invoking grpc_init() and use gRPC in the child
if and only if the child process first destroys all gRPC resources
inherited from the parent process and invokes grpc_shutdown().
Subsequent to this, the child will be able to re-initialize and use
gRPC. After fork, the parent process will be able to continue to use
existing gRPC resources such as channels and calls without interference
from the child process.

To facilitate gRPC Python applications meeting the above constraints,
gRPC Python will automatically destroy and shutdown all gRPC Core
resources in the child's post-fork handler, including cancelling
in-flight calls (see detailed design below). From the client's
perspective, the child process is now free to create new channels and
use gRPC.

1 files changed, 29 insertions, 0 deletions

diff --git a/src/python/grpcio/grpc/_cython/_cygrpc/fork_posix.pxd.pxi b/src/python/grpcio/grpc/_cython/_cygrpc/fork_posix.pxd.pxi
new file mode 100644
index 0000000000..a925bdd2e6
--- /dev/null
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/fork_posix.pxd.pxi
@@ -0,0 +1,29 @@
+# Copyright 2018 gRPC authors.
+#
+# 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.
+
+
+cdef extern from "pthread.h" nogil:
+    int pthread_atfork(
+        void (*prepare)() nogil,
+        void (*parent)() nogil,
+        void (*child)() nogil)
+
+
+cdef void __prefork() nogil
+
+
+cdef void __postfork_parent() nogil
+
+
+cdef void __postfork_child() nogil
\ No newline at end of file