# HG changeset patch
# User Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
# Date 1450164913 -3600
# Node ID 32a3860c799d87183e88aac5e6e8fbd5dc33428b
# Parent  b35e21fc1f9bb48a8c42d124ac29cc4f2612193a
[twisted] add request error handler to avoid finishing it twice

And avoid stack traces like::

  Traceback (most recent call last):
    File "/usr/lib/python2.7/threading.py", line 783, in __bootstrap
      self.__bootstrap_inner()
    File "/usr/lib/python2.7/threading.py", line 810, in __bootstrap_inner
      self.run()
    File "/usr/lib/python2.7/threading.py", line 763, in run
      self.__target(*self.__args, **self.__kwargs)
  --- <exception caught here> ---
    [...]
    File "/usr/lib/python2.7/dist-packages/twisted/python/threadpool.py", line 196, in _worker
      result = context.call(ctx, function, *args, **kwargs)
    File "/usr/lib/python2.7/dist-packages/twisted/python/context.py", line 118, in callWithContext
      return self.currentContext().callWithContext(ctx, func, *args, **kw)
    File "/usr/lib/python2.7/dist-packages/twisted/python/context.py", line 81, in callWithContext
      return func(*args,**kw)
    File "/home/me/envs/grshell-cw/cubicweb/statsd_logger.py", line 121, in __call__
      return self.callable(*args, **kw)
    File "/home/me/envs/grshell-cw/cubicweb/etwist/server.py", line 131, in render_request
      code=500, twisted_request=request)
    File "/home/me/envs/grshell-cw/cubicweb/etwist/http.py", line 22, in __init__
      self._finalize()
    File "/home/me/envs/grshell-cw/cubicweb/etwist/http.py", line 46, in _finalize
      self._twreq.finish()
    File "/usr/lib/python2.7/dist-packages/twisted/web/server.py", line 228, in finish
      return http.Request.finish(self)
    File "/usr/lib/python2.7/dist-packages/twisted/web/http.py", line 931, in finish
      "Request.finish called on a request after its connection was lost; "
  exceptions.RuntimeError: Request.finish called on a request after its connection was lost; use Request.notifyFinish to keep track of this.

diff -r b35e21fc1f9b -r 32a3860c799d cubicweb/etwist/http.py
--- a/cubicweb/etwist/http.py	Fri Sep 04 18:05:51 2015 +0200
+++ b/cubicweb/etwist/http.py	Tue Dec 15 08:35:13 2015 +0100
@@ -8,6 +8,7 @@
 
 
 
+
 class HTTPResponse(object):
     """An object representing an HTTP Response to be sent to the client.
     """
@@ -29,9 +30,14 @@
         # add content-length if not present
         if (self._headers_out.getHeader('content-length') is None
             and self._stream is not None):
-           self._twreq.setHeader('content-length', len(self._stream))
+            self._twreq.setHeader('content-length', len(self._stream))
 
     def _finalize(self):
+        # cw_failed is set on errors such as "connection aborted by client". In
+        # such cases, req.finish() was already called and calling it a twice
+        # would crash
+        if getattr(self._twreq, 'cw_failed', False):
+            return
         # we must set code before writing anything, else it's too late
         if self._code is not None:
             self._twreq.setResponseCode(self._code)
diff -r b35e21fc1f9b -r 32a3860c799d cubicweb/etwist/server.py
--- a/cubicweb/etwist/server.py	Fri Sep 04 18:05:51 2015 +0200
+++ b/cubicweb/etwist/server.py	Tue Dec 15 08:35:13 2015 +0100
@@ -21,6 +21,7 @@
 import traceback
 import threading
 from cgi import FieldStorage, parse_header
+from functools import partial
 
 from cubicweb.statsd_logger import statsd_timeit
 
@@ -89,8 +90,17 @@
         """Indicate which resource to use to process down the URL's path"""
         return self
 
+    def on_request_finished_ko(self, request, reason):
+        # annotate the twisted request so that we're able later to check for
+        # failure without having to dig into request's internal attributes such
+        # as _disconnected
+        request.cw_failed = True
+        self.warning('request finished abnormally: %s', reason)
+
     def render(self, request):
         """Render a page from the root resource"""
+        finish_deferred = request.notifyFinish()
+        finish_deferred.addErrback(partial(self.on_request_finished_ko, request))
         # reload modified files in debug mode
         if self.config.debugmode:
             self.config.uiprops.reload_if_needed()