feat: Process User-Agent strings (#5823)

Co-authored-by: Evandro Myller <22429+emyller@users.noreply.github.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: 3 people

api/app_analytics/constants.py

@@ -1,6 +1,6 @@
 from typing import get_args
 
-from app_analytics.types import Label, PeriodType
+from app_analytics.types import InputLabel, Label, PeriodType
 
 ANALYTICS_READ_BUCKET_SIZE = 15
 
@@ -15,9 +15,10 @@
 ) = get_args(PeriodType)
 
 # Optional headers sent from client SDK mapped to their respective labels.
-TRACK_HEADERS: dict[str, Label] = {
+TRACK_HEADERS: dict[str, InputLabel] = {
     "Flagsmith-Application-Name": "client_application_name",
     "Flagsmith-Application-Version": "client_application_version",
+    "Flagsmith-SDK-User-Agent": "sdk_user_agent",
     "User-Agent": "user_agent",
 }
 LABELS: tuple[str, ...] = tuple(str(label) for label in get_args(Label))

api/app_analytics/mappers.py

@@ -3,6 +3,7 @@
 from typing import Any, Iterable
 
 from django.http import HttpRequest
+from fastuaparser import parse_ua  # type: ignore[import-untyped]
 from influxdb_client.client.flux_table import FluxTable
 from pydantic import Field, create_model
 from pydantic.type_adapter import TypeAdapter
@@ -14,6 +15,7 @@
     AnnotatedAPIUsageBucket,
     AnnotatedAPIUsageKey,
     FeatureEvaluationCacheKey,
+    InputLabels,
     Labels,
     TrackFeatureEvaluationsByEnvironmentData,
     TrackFeatureEvaluationsByEnvironmentKwargs,
@@ -112,19 +114,37 @@ def map_flux_tables_to_feature_evaluation_data(
     ]
 
 
+def map_input_labels_to_labels(input_labels: InputLabels) -> Labels:
+    labels: Labels = {}
+    for label, value in input_labels.items():
+        if label == "sdk_user_agent":
+            labels["user_agent"] = value
+            continue
+        elif label == "user_agent":
+            # fastuaparser classifies unrecognized UAs as "Other" — assume these to
+            # represent server-side SDKs.
+            parsed_ua_string: str = parse_ua(value)
+            is_server_side_sdk = parsed_ua_string.startswith("Other")
+            # Skip browser SDKs that don't send the special header.
+            if not is_server_side_sdk:
+                continue
+        labels[label] = value
+    return labels
+
+
 def map_request_to_labels(request: HttpRequest) -> Labels:
     if not (
         get_client("local", local_eval=True)
         .get_environment_flags()
         .is_feature_enabled("sdk_metrics_labels")
     ):
         return {}
-    result: Labels = _RequestHeaderLabelsModel.model_validate(
+    labels: InputLabels = _RequestHeaderLabelsModel.model_validate(
         request.headers,
     ).model_dump(
         exclude_unset=True,
     )
-    return result
+    return map_input_labels_to_labels(labels)
 
 
 def map_feature_evaluation_cache_to_track_feature_evaluations_by_environment_kwargs(

api/app_analytics/types.py

@@ -54,4 +54,7 @@ class AnnotatedAPIUsageKey(NamedTuple):
     "user_agent",
 ]
 
+InputLabel = Label | Literal["sdk_user_agent"]
+
 Labels: TypeAlias = dict[Label, str]
+InputLabels: TypeAlias = dict[InputLabel, str]

api/poetry.lock

@@ -167,6 +167,7 @@ djangorestframework-simplejwt = "^5.3.1"
 structlog = "^24.4.0"
 prometheus-client = "^0.21.1"
 django_cockroachdb = "~4.2"
+fastuaparser = "^0.1.4"
 
 [tool.poetry.group.auth-controller]
 optional = true

api/pyproject.toml

@@ -565,6 +565,21 @@ def test_set_sdk_analytics_flags_with_identifier__influx__calls_expected(
                 "user_agent": "python-requests/2.31.0",
             },
         ),
+        (
+            {
+                "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36 Edg/134.0.0.0",
+            },
+            {},
+        ),
+        (
+            {
+                "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36 Edg/134.0.0.0",
+                "Flagsmith-SDK-User-Agent": "flagsmith-js-sdk/1.0.0",
+            },
+            {
+                "user_agent": "flagsmith-js-sdk/1.0.0",
+            },
+        ),
     ],
 )
 def test_sdk_analytics_flags_v1(