Set right content type header

synapse/http/request_metrics.py

@@ -16,13 +16,17 @@
 import logging
 import threading
 import traceback
-from typing import Dict, Mapping, Set, Tuple
+from typing import TYPE_CHECKING, Dict, Mapping, Optional, Set, Tuple
 
 from prometheus_client.core import Counter, Histogram
 
 from synapse.logging.context import current_context
+from synapse.logging.opentracing import get_prometheus_exemplar
 from synapse.metrics import LaterGauge
 
+if TYPE_CHECKING:
+    import opentracing
+
 logger = logging.getLogger(__name__)
 
 
@@ -143,7 +147,12 @@ LaterGauge(
 
 
 class RequestMetrics:
-    def start(self, time_sec: float, name: str, method: str) -> None:
+    def start(
+        self,
+        time_sec: float,
+        name: str,
+        method: str,
+    ) -> None:
         self.start_ts = time_sec
         self.start_context = current_context()
         self.name = name
@@ -162,7 +171,13 @@ class RequestMetrics:
         with _in_flight_requests_lock:
             _in_flight_requests.add(self)
 
-    def stop(self, time_sec: float, response_code: int, sent_bytes: int) -> None:
+    def stop(
+        self,
+        time_sec: float,
+        response_code: int,
+        sent_bytes: int,
+        span: Optional["opentracing.Span"],
+    ) -> None:
         with _in_flight_requests_lock:
             _in_flight_requests.discard(self)
 
@@ -193,7 +208,7 @@ class RequestMetrics:
         response_count.labels(self.method, self.name, tag).inc()
 
         response_timer.labels(self.method, self.name, tag, response_code_str).observe(
-            time_sec - self.start_ts
+            time_sec - self.start_ts, exemplar=get_prometheus_exemplar(span)
         )
 
         resource_usage = context.get_resource_usage()

synapse/http/site.py

@@ -487,7 +487,9 @@ class SynapseRequest(Request):
             self._opentracing_span.finish()
 
         try:
-            self.request_metrics.stop(self.finish_time, self.code, self.sentLength)
+            self.request_metrics.stop(
+                self.finish_time, self.code, self.sentLength, self._opentracing_span
+            )
         except Exception as e:
             logger.warning("Failed to stop metrics: %r", e)
 

synapse/logging/opentracing.py

@@ -672,6 +672,20 @@ def active_span() -> Optional["opentracing.Span"]:
     return opentracing.tracer.active_span
 
 
+def get_prometheus_exemplar(
+    span: Optional["opentracing.Span"] = None,
+) -> Optional[Dict[str, str]]:
+    if not span:
+        span = active_span()
+
+    if not span:
+        return None
+
+    trace_id = getattr(span, "trace_id", None)
+
+    return {"trace_id": f"{trace_id:x}"}
+
+
 @ensure_active_span("set a tag")
 def set_tag(key: str, value: Union[str, bool, int, float]) -> None:
     """Sets a tag on the active span"""

synapse/metrics/_twisted_exposition.py

@@ -13,12 +13,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from prometheus_client import REGISTRY, CollectorRegistry, generate_latest
+from prometheus_client import REGISTRY, CollectorRegistry
+from prometheus_client.openmetrics.exposition import generate_latest
 
 from twisted.web.resource import Resource
 from twisted.web.server import Request
 
-CONTENT_TYPE_LATEST = "text/plain; version=0.0.4; charset=utf-8"
+CONTENT_TYPE_LATEST = "application/openmetrics-text; version=1.0.0; charset=utf-8"
 
 
 class MetricsResource(Resource):