Make EPIPE tracebacks go away (#595)

These errors aren't very helpful and they tend to fill up logs. They could be
caused by something as innocent as `curl -N http://localhost:6006/ | head`. It
could also be caused by firewalls, or perhaps the browser abruptly navigating
somewhere else. So we wouldn't want users to mistake these as meaningful when
troubleshooting.

Author: jart

Diff for: tensorboard/main.py

@@ -21,6 +21,7 @@
 from __future__ import division
 from __future__ import print_function
 
+import errno
 import os
 import socket
 import sys
@@ -220,7 +221,7 @@ def make_simple_server(tb_app, host=None, port=None, path_prefix=None):
     tf.logging.error(msg)
     print(msg)
     raise socket_error
-
+  server.handle_error = _handle_error
   final_port = server.socket.getsockname()[1]
   tensorboard_url = 'http://%s:%d%s' % (final_host, final_port, path_prefix)
   return server, tensorboard_url
@@ -240,6 +241,18 @@ def run_simple_server(tb_app):
   server.serve_forever()
 
 
+# Kludge to override a SocketServer.py method so we can get rid of noisy
+# EPIPE errors. They're kind of a red herring as far as errors go. For
+# example, `curl -N http://localhost:6006/ | head` will cause an EPIPE.
+def _handle_error(unused_request, client_address):
+  exc_info = sys.exc_info()
+  e = exc_info[1]
+  if isinstance(e, IOError) and e.errno == errno.EPIPE:
+    tf.logging.warn('EPIPE caused by %s:%d in HTTP serving' % client_address)
+  else:
+    tf.logging.error('HTTP serving error', exc_info=exc_info)
+
+
 def main(unused_argv=None):
   util.setup_logging()
   if FLAGS.inspect: