scrub repetitive gen.py, coroutine.py frames from coroutine tracebacks

when logging exceptions

jupyterhub/app.py

@@ -26,7 +26,7 @@ import tornado.httpserver
 import tornado.options
 from tornado.httpclient import HTTPError
 from tornado.ioloop import IOLoop, PeriodicCallback
-from tornado.log import LogFormatter, app_log, access_log, gen_log
+from tornado.log import app_log, access_log, gen_log
 from tornado import gen, web
 
 import IPython
@@ -47,6 +47,7 @@ from .handlers.static import CacheControlStaticFilesHandler
 
 from . import orm
 from ._data import DATA_FILES_PATH
+from .log import CoroutineLogFormatter
 from .traitlets import URLPrefix
 from .utils import (
     url_path_join,
@@ -350,7 +351,7 @@ class JupyterHub(Application):
     
     handlers = List()
     
-    _log_formatter_cls = LogFormatter
+    _log_formatter_cls = CoroutineLogFormatter
     http_server = None
     proxy_process = None
     io_loop = None

jupyterhub/log.py

@@ -0,0 +1,40 @@
+"""logging utilities"""
+# Copyright (c) Jupyter Development Team.
+# Distributed under the terms of the Modified BSD License.
+
+import traceback
+
+from tornado.log import LogFormatter
+
+def coroutine_traceback(typ, value, tb):
+    """Scrub coroutine frames from a traceback
+    
+    Coroutine tracebacks have a bunch of identical uninformative frames at each yield point.
+    This removes those extra frames, so tracebacks should be easier to read.
+    This might be a horrible idea.
+    
+    Returns a list of strings (like traceback.format_tb)
+    """
+    all_frames = traceback.extract_tb(tb)
+    useful_frames = []
+    for frame in all_frames:
+        if frame[0] == '<string>' and frame[2] == 'raise_exc_info':
+            continue
+        # start out conservative with filename + function matching
+        # maybe just filename matching would be sufficient
+        elif frame[0].endswith('tornado/gen.py') and frame[2] in {'run', 'wrapper'}:
+            continue
+        elif frame[0].endswith('tornado/concurrent.py') and frame[2] == 'result':
+            continue
+        useful_frames.append(frame)
+    tb_list = ['Traceback (most recent call last):\n']
+    tb_list.extend(traceback.format_list(useful_frames))
+    tb_list.extend(traceback.format_exception_only(typ, value))
+    return tb_list
+
+
+class CoroutineLogFormatter(LogFormatter):
+    """Log formatter that scrubs coroutine frames"""
+    def formatException(self, exc_info):
+        return ''.join(coroutine_traceback(*exc_info))
+