Add a span to background processes

synapse/logging/opentracing.py

@@ -526,6 +526,19 @@ def start_active_span_from_edu(
     return scope
 
 
+def get_active_span_context():
+    """Gets the active span's context, if any.
+    """
+    if not opentracing:
+        return None
+
+    active_span = opentracing.tracer.active_span
+    if not active_span:
+        return None
+
+    return active_span.context
+
+
 # Opentracing setters for tags, logs, etc
 
 

synapse/metrics/background_process_metrics.py

@@ -25,6 +25,10 @@ from twisted.internet import defer
 from twisted.python.failure import Failure
 
 from synapse.logging.context import LoggingContext, PreserveLoggingContext
+from synapse.logging.opentracing import (
+    get_active_span_context,
+    start_active_span_follows_from,
+)
 
 if TYPE_CHECKING:
     import resource
@@ -188,6 +192,8 @@ def run_as_background_process(desc, func, *args, **kwargs):
         follow the synapse logcontext rules.
     """
 
+    previous_span_context = get_active_span_context()
+
     @defer.inlineCallbacks
     def run():
         with _bg_metrics_lock:
@@ -197,7 +203,7 @@ def run_as_background_process(desc, func, *args, **kwargs):
         _background_process_start_count.labels(desc).inc()
         _background_process_in_flight_count.labels(desc).inc()
 
-        with BackgroundProcessLoggingContext(desc) as context:
+        with BackgroundProcessLoggingContext(desc, previous_span_context) as context:
             context.request = "%s-%i" % (desc, count)
 
             try:
@@ -250,12 +256,14 @@ class BackgroundProcessLoggingContext(LoggingContext):
     processes.
     """
 
-    __slots__ = ["_proc"]
+    __slots__ = ["_proc", "_span", "_previous_spans"]
 
-    def __init__(self, name: str):
+    def __init__(self, name: str, previous_span_context):
         super().__init__(name)
 
         self._proc = _BackgroundProcess(name, self)
+        self._span = None
+        self._previous_spans = [previous_span_context] if previous_span_context else []
 
     def start(self, rusage: "Optional[resource._RUsage]"):
         """Log context has started running (again).
@@ -269,10 +277,20 @@ class BackgroundProcessLoggingContext(LoggingContext):
         with _bg_metrics_lock:
             _background_processes_active_since_last_scrape.add(self._proc)
 
+    def __enter__(self) -> LoggingContext:
+        context = super().__enter__()
+
+        self._span = start_active_span_follows_from(self.name, self._previous_spans)
+        self._span.__enter__()
+
+        return context
+
     def __exit__(self, type, value, traceback) -> None:
         """Log context has finished.
         """
 
+        self._span.__exit__(type, value, traceback)
+
         super().__exit__(type, value, traceback)
 
         # The background process has finished. We explictly remove and manually