Added function and example for telemetry streaming of a IOS-XR 6.1.1 box

Author: kkumara3

.gitignore

@@ -1,3 +1,3 @@
-ems.pem
+*.pem
 .DS_STORE
 *.pyc

examples/telemetry_collector.py

@@ -0,0 +1,19 @@
+""" Basic collector for telemetry.
+Initiate a gRPC dial-in telemetry channel, subscribe to a stream,
+and output to display. Converts from protobuf to JSON for display.
+"""
+
+import sys
+sys.path.insert(0, '../')
+from lib.cisco_grpc_client import CiscoGRPCClient
+import json
+
+client = CiscoGRPCClient('10.200.96.16', 57400, 100, 'mdt', 'f33dm3d4t4')
+subscription_id = 'sub1'
+recv_count = 0
+for segment in client.get_subscription(subscription_id):
+	recv_count += 1
+	print json.dumps(segment, indent=4, separators=(',', ': '))
+	print 'End Telemetry Segment'
+	print str(recv_count) + ' Segments Received'
+

lib/cisco_grpc_client.py

@@ -1,6 +1,9 @@
 import grpc
 from grpc.beta import implementations
 import ems_grpc_pb2
+import protobuf_json
+import ems_grpc_pb2
+import telemetry_message_pb2
 
 class CiscoGRPCClient(object):
     def __init__(self, host, port, timeout, user, password, creds=None, options=None):
@@ -59,6 +62,26 @@ def getconfig(self, path):
             objects += response.yangjson
         return objects
 
+    def get_subscription(self, sub_id):
+        """Telemetry subscription function
+            :param sub_id: Subscription ID
+            :type: string
+            :return: Returns discrete values emitted by telemetry stream
+            :rtype: JSON formatted string
+        """
+        sub_args = ems_grpc_pb2.CreateSubsArgs(ReqId=1, encode=3, subidstr=sub_id)
+        stream = self._stub.CreateSubs(sub_args, timeout=self._timeout, metadata=self._metadata)
+        self._channel.subscribe(self.connectivity_handler, True)
+        for segment in stream:
+            # Go straight for telemetry data
+            telemetry_pb = telemetry_message_pb2.Telemetry()
+            telemetry_pb.ParseFromString(segment.data)
+            # Return in JSON format instead of protobuf.
+            yield protobuf_json.pb2json(telemetry_pb)
+
+    def connectivity_handler(self, result):
+        print result
+
     def mergeconfig (self, yangjson):
         """Merge grpc call equivalent  of PATCH RESTconf call
             :param data: JSON