Channelz Python wrapper implementation

* Expose the C-Core API in Cython layer
* Handle the object translation
* Create a separate package for Channelz specifically
* Handle nullptr and raise exception if seen one
* Translate C++ Channelz unit tests
* Adding 5 more invalid query unit tests

Adding peripheral utility for grpcio-channelz package
* Add to `pylint_code.sh`
* Add to Python build script
* Add to artifact build script
* Add to Bazel
* Add to Sphinx module list

5 files changed, 71 insertions, 1 deletions

diff --git a/src/python/grpcio/grpc/_cython/BUILD.bazel b/src/python/grpcio/grpc/_cython/BUILD.bazel
index cfd3a51d9b..e318298d0a 100644
--- a/src/python/grpcio/grpc/_cython/BUILD.bazel
+++ b/src/python/grpcio/grpc/_cython/BUILD.bazel
@@ -12,6 +12,7 @@ pyx_library(
         "_cygrpc/grpc_string.pyx.pxi",
         "_cygrpc/arguments.pyx.pxi",
         "_cygrpc/call.pyx.pxi",
+        "_cygrpc/channelz.pyx.pxi",
         "_cygrpc/channel.pyx.pxi",
         "_cygrpc/credentials.pyx.pxi",
         "_cygrpc/completion_queue.pyx.pxi",
diff --git a/src/python/grpcio/grpc/_cython/_cygrpc/channelz.pyx.pxi b/src/python/grpcio/grpc/_cython/_cygrpc/channelz.pyx.pxi
new file mode 100644
index 0000000000..572a473d3e
--- /dev/null
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/channelz.pyx.pxi
@@ -0,0 +1,56 @@
+# Copyright 2018 The 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.
+
+
+def channelz_get_top_channels(start_channel_id):
+    cdef char *c_returned_str = grpc_channelz_get_top_channels(start_channel_id)
+    if c_returned_str == NULL:
+        raise ValueError('Failed to get top channels, please ensure your start_channel_id==%s is valid' % start_channel_id)
+    return c_returned_str
+    
+def channelz_get_servers(start_server_id):
+    cdef char *c_returned_str = grpc_channelz_get_servers(start_server_id)
+    if c_returned_str == NULL:
+        raise ValueError('Failed to get servers, please ensure your start_server_id==%s is valid' % start_server_id)
+    return c_returned_str
+    
+def channelz_get_server(server_id):
+    cdef char *c_returned_str = grpc_channelz_get_server(server_id)
+    if c_returned_str == NULL:
+        raise ValueError('Failed to get the server, please ensure your server_id==%s is valid' % server_id)
+    return c_returned_str
+    
+def channelz_get_server_sockets(server_id, start_socket_id):
+    cdef char *c_returned_str = grpc_channelz_get_server_sockets(server_id, start_socket_id)
+    if c_returned_str == NULL:
+        raise ValueError('Failed to get server sockets, please ensure your server_id==%s and start_socket_id==%s is valid' % (server_id, start_socket_id))
+    return c_returned_str
+    
+def channelz_get_channel(channel_id):
+    cdef char *c_returned_str = grpc_channelz_get_channel(channel_id)
+    if c_returned_str == NULL:
+        raise ValueError('Failed to get the channel, please ensure your channel_id==%s is valid' % (channel_id))
+    return c_returned_str
+    
+def channelz_get_subchannel(subchannel_id):
+    cdef char *c_returned_str = grpc_channelz_get_subchannel(subchannel_id)
+    if c_returned_str == NULL:
+        raise ValueError('Failed to get the subchannel, please ensure your subchannel_id==%s is valid' % (subchannel_id))
+    return c_returned_str
+    
+def channelz_get_socket(socket_id):
+    cdef char *c_returned_str = grpc_channelz_get_socket(socket_id)
+    if c_returned_str == NULL:
+        raise ValueError('Failed to get the socket, please ensure your socket_id==%s is valid' % (socket_id))
+    return c_returned_str
diff --git a/src/python/grpcio/grpc/_cython/_cygrpc/grpc.pxi b/src/python/grpcio/grpc/_cython/_cygrpc/grpc.pxi
index 23428f0b0c..ccd46dbf92 100644
--- a/src/python/grpcio/grpc/_cython/_cygrpc/grpc.pxi
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/grpc.pxi
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 cimport libc.time
+from libc.stdint cimport intptr_t
 
 
 # Typedef types with approximately the same semantics to provide their names to
@@ -391,6 +392,15 @@ cdef extern from "grpc/grpc.h":
   void grpc_server_cancel_all_calls(grpc_server *server) nogil
   void grpc_server_destroy(grpc_server *server) nogil
 
+  char* grpc_channelz_get_top_channels(intptr_t start_channel_id)
+  char* grpc_channelz_get_servers(intptr_t start_server_id)
+  char* grpc_channelz_get_server(intptr_t server_id)
+  char* grpc_channelz_get_server_sockets(intptr_t server_id,
+                                         intptr_t start_socket_id)
+  char* grpc_channelz_get_channel(intptr_t channel_id)
+  char* grpc_channelz_get_subchannel(intptr_t subchannel_id)
+  char* grpc_channelz_get_socket(intptr_t socket_id)
+
 
 cdef extern from "grpc/grpc_security.h":
 
diff --git a/src/python/grpcio/grpc/_cython/cygrpc.pyx b/src/python/grpcio/grpc/_cython/cygrpc.pyx
index ae5c07bfc8..9ab919375c 100644
--- a/src/python/grpcio/grpc/_cython/cygrpc.pyx
+++ b/src/python/grpcio/grpc/_cython/cygrpc.pyx
@@ -35,6 +35,7 @@ include "_cygrpc/server.pyx.pxi"
 include "_cygrpc/tag.pyx.pxi"
 include "_cygrpc/time.pyx.pxi"
 include "_cygrpc/_hooks.pyx.pxi"
+include "_cygrpc/channelz.pyx.pxi"
 
 include "_cygrpc/grpc_gevent.pyx.pxi"
 
diff --git a/src/python/grpcio/grpc/_server.py b/src/python/grpcio/grpc/_server.py
index 7276a7fd90..fea1ca8da6 100644
--- a/src/python/grpcio/grpc/_server.py
+++ b/src/python/grpcio/grpc/_server.py
@@ -828,7 +828,9 @@ class _Server(grpc.Server):
         return _stop(self._state, grace)
 
     def __del__(self):
-        _stop(self._state, None)
+        if hasattr(self, '_state'):
+            _stop(self._state, None)
+            del self._state
 
 
 def create_server(thread_pool, generic_rpc_handlers, interceptors, options,