Reduce federation logging on success (#7321)

Splitting based on the response code means we can avoid double logging here and identical information from line 164 while still logging at info if we don't get a good response and need to retry.

changelog.d/7321.misc

@@ -0,0 +1 @@
+Reduce logging verbosity for successful federation requests.

synapse/http/matrixfederationclient.py

@@ -434,6 +434,20 @@ class MatrixFederationHttpClient(object):
                         logger.info("Failed to send request: %s", e)
                         raise_from(RequestSendFailed(e, can_retry=True), e)
 
+                    incoming_responses_counter.labels(method_bytes, response.code).inc()
+
+                    set_tag(tags.HTTP_STATUS_CODE, response.code)
+
+                    if 200 <= response.code < 300:
+                        logger.debug(
+                            "{%s} [%s] Got response headers: %d %s",
+                            request.txn_id,
+                            request.destination,
+                            response.code,
+                            response.phrase.decode("ascii", errors="replace"),
+                        )
+                        pass
+                    else:
                         logger.info(
                             "{%s} [%s] Got response headers: %d %s",
                             request.txn_id,
@@ -441,14 +455,6 @@ class MatrixFederationHttpClient(object):
                             response.code,
                             response.phrase.decode("ascii", errors="replace"),
                         )
-
-                    incoming_responses_counter.labels(method_bytes, response.code).inc()
-
-                    set_tag(tags.HTTP_STATUS_CODE, response.code)
-
-                    if 200 <= response.code < 300:
-                        pass
-                    else:
                         # :'(
                         # Update transactions table?
                         d = treq.content(response)