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

+Reduce logging verbosity for successful federation requests.

synapse/http/matrixfederationclient.py

@@ -434,21 +434,27 @@ class MatrixFederationHttpClient(object):
                         logger.info("Failed to send request: %s", e)
                         raise_from(RequestSendFailed(e, can_retry=True), e)
 
-                    logger.info(
-                        "{%s} [%s] Got response headers: %d %s",
-                        request.txn_id,
-                        request.destination,
-                        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:
+                        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,
+                            request.destination,
+                            response.code,
+                            response.phrase.decode("ascii", errors="replace"),
+                        )
                         # :'(
                         # Update transactions table?
                         d = treq.content(response)