Add links for trace exporter envelopes (census-instrumentation#936)

Author: lzchen

contrib/opencensus-ext-azure/CHANGELOG.md

@@ -6,6 +6,8 @@
   ([#930](https://github.com/census-instrumentation/opencensus-python/pull/930))
 - Attach rate metrics for VM
   ([#935](https://github.com/census-instrumentation/opencensus-python/pull/935))
+- Add links in properties for trace exporter envelopes
+  ([#936](https://github.com/census-instrumentation/opencensus-python/pull/936))
 
 ## 1.0.4
 Released 2020-06-29

contrib/opencensus-ext-azure/examples/traces/config.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import json
 import logging
 
 from opencensus.common.schedule import QueueExitEvent
@@ -146,7 +147,13 @@ def span_data_to_envelope(self, sd):
             else:
                 data.type = 'INPROC'
                 data.success = True
-        # TODO: links, tracestate, tags
+        if sd.links:
+            links = []
+            for link in sd.links:
+                links.append(
+                    {"operation_Id": link.trace_id, "id": link.span_id})
+            data.properties["_MS.links"] = json.dumps(links)
+        # TODO: tracestate, tags
         for key in sd.attributes:
             # This removes redundant data from ApplicationInsights
             if key.startswith('http.'):

contrib/opencensus-ext-azure/opencensus/ext/azure/trace_exporter/__init__.py

@@ -12,13 +12,15 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import json
 import os
 import shutil
 import unittest
 
 import mock
 
 from opencensus.ext.azure import trace_exporter
+from opencensus.trace.link import Link
 
 TEST_FOLDER = os.path.abspath('.test.exporter')
 
@@ -141,7 +143,9 @@ def test_span_data_to_envelope(self):
             start_time='2010-10-24T07:28:38.123456Z',
             end_time='2010-10-24T07:28:38.234567Z',
             stack_trace=None,
-            links=None,
+            links=[
+                Link('6e0c63257de34c90bf9efcd03927272e', '6e0c63257de34c91')
+            ],
             status=Status(0),
             annotations=None,
             message_events=None,
@@ -188,6 +192,17 @@ def test_span_data_to_envelope(self):
         self.assertEqual(
             envelope.data.baseType,
             'RemoteDependencyData')
+        json_dict = json.loads(
+            envelope.data.baseData.properties["_MS.links"]
+        )[0]
+        self.assertEqual(
+            json_dict["id"],
+            "6e0c63257de34c91",
+        )
+        self.assertEqual(
+            json_dict["operation_Id"],
+            "6e0c63257de34c90bf9efcd03927272e",
+        )
 
         # SpanKind.CLIENT unknown type
         envelope = exporter.span_data_to_envelope(SpanData(