Make Jaeger fully configurable (#5694)

* Allow Jaeger to be configured

* Update sample config

synapse/logging/opentracing.py

@@ -228,13 +228,16 @@ def init_tracer(config):
     # Include the worker name
     name = config.worker_name if config.worker_name else "master"
 
+    # Pull out the jaeger config if it was given. Otherwise set it to something sensible.
+    # See https://github.com/jaegertracing/jaeger-client-python/blob/master/jaeger_client/config.py
+
     set_homeserver_whitelist(config.opentracer_whitelist)
-    jaeger_config = JaegerConfig(
-        config={"sampler": {"type": "const", "param": 1}, "logging": True},
+
+    JaegerConfig(
+        config=config.jaeger_config,
         service_name="{} {}".format(config.server_name, name),
         scope_manager=LogContextScopeManager(config),
-    )
-    jaeger_config.initialize_tracer()
+    ).initialize_tracer()
 
     # Set up tags to be opentracing's tags
     global tags