chore(peer.service): add mongodb.db as precursor for mongo (#6225)

This change adds the span tag `mongodb.db` as a precursor for Mongo
databases, and ensures that the `peer.service` tag is updated when it is
present.

## Checklist

- [x] Change(s) are motivated and described in the PR description.
- [x] Testing strategy is described if automated tests are not included
in the PR.
- [x] Risk is outlined (performance impact, potential for breakage,
maintainability, etc).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] [Library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
are followed. If no release note is required, add label
`changelog/no-changelog`.
- [x] Documentation is included (in-code, generated user docs, [public
corp docs](https://github.com/DataDog/documentation/)).
- [x] Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist

- [ ] Title is accurate.
- [ ] No unnecessary changes are introduced.
- [ ] Description motivates each change.
- [ ] Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes unless absolutely necessary.
- [ ] Testing strategy adequately addresses listed risk(s).
- [ ] Change is maintainable (easy to change, telemetry, documentation).
- [ ] Release note makes sense to a user of the library.
- [ ] Reviewer has explicitly acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment.
- [ ] Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

Author: tabgok

ddtrace/settings/peer_service.py

@@ -11,7 +11,7 @@ class PeerServiceConfig(object):
     source_tag_name = "_dd.peer.service.source"
     tag_name = "peer.service"
     enabled_span_kinds = {SpanKind.CLIENT, SpanKind.PRODUCER}
-    prioritized_data_sources = ["messaging.kafka.bootstrap.servers", "db.name", "rpc.service", "out.host"]
+    prioritized_data_sources = ["messaging.kafka.bootstrap.servers", "db.name", "mongodb.db", "rpc.service", "out.host"]
 
     def __init__(self, set_defaults_enabled=None, peer_service_mapping=None):
         self._set_defaults_enabled = set_defaults_enabled

tests/contrib/mongoengine/test.py

@@ -219,6 +219,16 @@ def test_span_name_v1_schema(self):
         assert len(spans) == 1
         assert spans[0].name == "mongodb.query"
 
+    @TracerTestCase.run_in_subprocess(env_overrides=dict(DD_TRACE_SPAN_ATTRIBUTE_SCHEMA="v1"))
+    def test_peer_service_tagging(self):
+        tracer = self.get_tracer_and_connect()
+        Artist.drop_collection()
+
+        spans = tracer.pop()
+        assert len(spans) == 1
+        assert spans[0].get_tag("mongodb.db") == "test"
+        assert spans[0].get_tag("peer.service") == "test"
+
 
 class TestMongoEnginePatchConnectDefault(TracerTestCase, MongoEngineCore):
     """Test suite with a global Pin for the connect function with the default configuration"""

tests/contrib/pymongo/test.py

@@ -654,6 +654,21 @@ def test_operation_name_v1_schema(self):
         assert len(spans) == 1
         assert spans[0].name == "mongodb.query"
 
+    @TracerTestCase.run_in_subprocess(env_overrides=dict(DD_TRACE_SPAN_ATTRIBUTE_SCHEMA="v1"))
+    def test_peer_service_tagging(self):
+        tracer = DummyTracer()
+        client = pymongo.MongoClient(port=MONGO_CONFIG["port"])
+        Pin.get_from(client).clone(tracer=tracer).onto(client)
+        # We do not wish to trace tcp spans here
+        Pin.get_from(pymongo.server.Server).remove_from(pymongo.server.Server)
+        db_name = "testdb"
+        client[db_name].drop_collection("whatever")
+        spans = tracer.pop()
+        assert len(spans) == 1
+        for span in spans:
+            assert span.get_tag("mongodb.db") == db_name
+            assert span.get_tag("peer.service") == db_name
+
     def test_patch_with_disabled_tracer(self):
         tracer, client = self.get_tracer_and_client()
         tracer.configure(enabled=False)