Disable tracer if not configured

synapse/config/tracer.py

@@ -65,6 +65,7 @@ def init_tracing(config):
         name to the homeserver's.
     """
 
+    if config.tracer_config.get("tracer_enabled", False):
         jaeger_config = JaegerConfig(
             config={ 
                 'sampler': {
@@ -76,5 +77,14 @@ def init_tracing(config):
             service_name=config.server_name + "_new",
             scope_manager=LogContextScopeManager(config),
         )
+    else: # The tracer is not configured so we instantiate a noop tracer
+        jaeger_config = JaegerConfig(
+            config={
+                'sampler': {
+                    'type': 'const',
+                    'param': 0,
+                }
+            }
+        )
 
     return jaeger_config.initialize_tracer()