Re: self.channel.writeHeaders(version, code, reason, headers)\nbuiltins.AttributeError: \'NoneType\' object has no attribute \'writeHeaders\'\
Waqar Khan <[email protected]> Sun, 4 Aug 2019 23:26:01 -0400
| Newsgroups | gmane.comp.python.twisted |
|---|---|
| Message-ID | <CAJuJkHN0A1syyxhuQWw8eRQwZVpChMKkOPfpWe++YV113TmDzQ@mail.gmail.com> |
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Hi Glyph,
Here is the minimal version
class FooResource(resource.Resource):
def render_GET(request):
future = asyncio.ensure_future(self.fetch_response(request))
// some async await functions
d = Deferred.fromFuture(future)
d.addCallback(print_json_response, request) // this is
actually where the error is triggered.
d.addErrback(lambda failure:
failure.trap(defer.CancelledError))
finished_errback = request.notifyFinish()
finished_errback.addErrback(self.handle_cancel, d) // simple
logs and cancels d by d.cancel()
return NOT_DONE_YET
The traceback is like
'Traceback (most recent call last):\n File
"/usr/local/Cellar/python/3.7.1/Frameworks/Python.framework/Versions/3.7/lib/python3.7/asyncio/events.py",
line 88, in _run\n self._context.run(self._callback, *self._args)\n
File "/usr/local/lib/python3.7/site-packages/twisted/internet/defer.py",
line 827, in adapt\n adapt.actual.callback(extracted)\n File
"/usr/local/lib/python3.7/site-packages/twisted/internet/defer.py", line
460, in callback\n self._startRunCallbacks(result)\n File
"/usr/local/lib/python3.7/site-packages/twisted/internet/defer.py", line
568, in _startRunCallbacks\n self._runCallbacks()\n--- <exception caught
here> ---\n File
"/usr/local/lib/python3.7/site-packages/twisted/internet/defer.py", line
654, in _runCallbacks\n current.result = callback(current.result, *args,
**kw)\n File "/Users/wqKhan/twisted_eg/parse_response.py", line 3, in
print_json_response\n *print_json_response*(response, request)\n File
"/Users/wqKhan/twisted_eg/parse_response.py", line 21, in
*print_json_response*\n request.finish()\n File
"/usr/local/lib/python3.7/site-packages/twisted/web/server.py", line 268,
in finish\n return http.Request.finish(self)\n File
"/usr/local/lib/python3.7/site-packages/twisted/web/http.py", line 1071, in
finish\n "Request.finish called on a request after its connection was
lost; "\nbuiltins.RuntimeError: Request.finish called on a request after
its connection was lost; use Request.notifyFinish to keep track of this.\n'
On Sun, Aug 4, 2019 at 10:36 PM Glyph <[email protected]> wrote:
>
>
> > On Aug 4, 2019, at 5:57 PM, Waqar Khan <[email protected]> wrote:
> >
> > Hi Glyph,
> > Thanks for the suggestion.
> > I tried the suggestion.. While it fixes the self.channel NoneType
> issue.. It creates another issue.
> >
> > Traceback (most recent call last):
> > File
> "/usr/local/Cellar/python/3.7.1/Frameworks/Python.framework/Versions/3.7/lib/python3.7/asyncio/events.py",
> line 88, in _run
> > self._context.run(self._callback, *self._args)
> > File
> "/usr/local/lib/python3.7/site-packages/twisted/internet/defer.py", line
> 827, in adapt
> > adapt.actual.callback(extracted)
> > File
> "/usr/local/lib/python3.7/site-packages/twisted/internet/defer.py", line
> 460, in callback
> > self._startRunCallbacks(result)
> > File
> "/usr/local/lib/python3.7/site-packages/twisted/internet/defer.py", line
> 568, in _startRunCallbacks
> > self._runCallbacks()
> > --- <exception caught here> ---
> > File
> "/usr/local/lib/python3.7/site-packages/twisted/internet/defer.py", line
> 654, in _runCallbacks
> > current.result = callback(current.result, *args, **kw)
> > ......
> > request.finish()
> > File "/usr/local/lib/python3.7/site-packages/twisted/web/server.py",
> line 268, in finish
> > return http.Request.finish(self)
> > File "/usr/local/lib/python3.7/site-packages/twisted/web/http.py",
> line 1071, in finish
> > "Request.finish called on a request after its connection was lost; "
> > builtins.RuntimeError: Request.finish called on a request after its
> connection was lost; use Request.notifyFinish to keep track of this.
>
> Oh, hrm. The idea here is that any code that returns NOT_DONE_YET (i.e.
> does asynchronous work to generate a response) should also be tracking
> whether it needs to call `.finish()` by watching a `.notifyFinish()`
> Deferred. I bet that there are plenty of resources in Twisted which don't
> follow this rule, and we should fix those; but possibly we should also make
> this error message less stern. Do you have a minimal example?
>
> > I have got some handle on the issue. I was wondering if you have any
> advise on how to debug the issue.
> > Somewhere in the codebase are async/await code (from asyncio world).
> Hence, when the connection is closed down by client, seems like those
> pending coroutines are lingering on.
>
> This, I have no idea about. What tasks are you starting, when are you
> expecting them to get cleaned up, what are they blocking on, how do these
> interact with Twisted? There are a couple dozen questions I'd have to know
> the answer to in order to even begin debugging this. If you cancel all the
> outstanding tasks and look at their tracebacks when exiting it might give
> you more of a sense of where they're stuck...
>
> -g
>
> _______________________________________________
> Twisted-Python mailing list
> [email protected]
> https://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python
>
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<div dir=3D"ltr">Hi Glyph,<div>=C2=A0 =C2=A0Here is the minimal version</di=
v><div><br></div><div><br></div><div>class FooResource(resource.Resource):<=
/div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0def render_GET(request):</div><div>=C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 future =3D asyncio.ensure_fut=
ure(self.fetch_response(request)) // some async await functions</div><div>=
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 d =3D=C2=A0Deferred.fromFu=
ture(future)</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0=C2=
=A0d.addCallback(print_json_response, request) // this is actually where th=
e error is triggered.</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0=C2=A0d.addErrback(lambda failure: failure.trap(defer.CancelledError)=
)</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0=C2=A0finished_=
errback =3D request.notifyFinish()</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 finished_errback.addErrback(self.handle_cancel, d) // =
simple logs and cancels d by d.cancel()</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 return NOT_DONE_YET</div><div><br></div><div>The t=
raceback is like</div><div>'Traceback (most recent call last):\n =C2=A0=
File "/usr/local/Cellar/python/3.7.1/Frameworks/Python.framework/Versi=
ons/3.7/lib/python3.7/asyncio/events.py", line 88, in _run\n =C2=A0 =
=C2=A0self._context.run(self._callback, *self._args)\n =C2=A0File "/us=
r/local/lib/python3.7/site-packages/twisted/internet/defer.py", line 8=
27, in adapt\n =C2=A0 =C2=A0adapt.actual.callback(extracted)\n =C2=A0File &=
quot;/usr/local/lib/python3.7/site-packages/twisted/internet/defer.py"=
, line 460, in callback\n =C2=A0 =C2=A0self._startRunCallbacks(result)\n =
=C2=A0File "/usr/local/lib/python3.7/site-packages/twisted/internet/de=
fer.py", line 568, in _startRunCallbacks\n =C2=A0 =C2=A0self._runCallb=
acks()\n--- <exception caught here> ---\n =C2=A0File "/usr/local=
/lib/python3.7/site-packages/twisted/internet/defer.py", line 654, in =
_runCallbacks\n =C2=A0 =C2=A0current.result =3D callback(current.result, *a=
rgs, **kw)\n =C2=A0File "/Users/wqKhan/twisted_eg/parse_response.py&qu=
ot;, line 3, in print_json_response\n=C2=A0 =C2=A0 <b>print_json_response</=
b>(response, request)\n =C2=A0File "/Users/wqKhan/twisted_eg/parse_res=
ponse.py", line 21, in <b>print_json_response</b>\n =C2=A0 =C2=A0reque=
st.finish()\n =C2=A0File "/usr/local/lib/python3.7/site-packages/twist=
ed/web/server.py", line 268, in finish\n =C2=A0 =C2=A0return http.Requ=
est.finish(self)\n =C2=A0File "/usr/local/lib/python3.7/site-packages/=
twisted/web/http.py", line 1071, in finish\n =C2=A0 =C2=A0"Reques=
t.finish called on a request after its connection was lost; "\nbuiltin=
s.RuntimeError: Request.finish called on a request after its connection was=
lost; use Request.notifyFinish to keep track of this.\n'</div><div><br=
></div><div><br></div></div><br><div class=3D"gmail_quote"><div dir=3D"ltr"=
class=3D"gmail_attr">On Sun, Aug 4, 2019 at 10:36 PM Glyph <<a href=3D"=
mailto:[email protected]" target=3D"_blank">[email protected]</=
a>> wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0p=
x 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><b=
r>
<br>
> On Aug 4, 2019, at 5:57 PM, Waqar Khan <<a href=3D"mailto:wk80333@g=
mail.com" target=3D"_blank">[email protected]</a>> wrote:<br>
> <br>
> Hi Glyph,<br>
>=C2=A0 =C2=A0Thanks for the suggestion.<br>
> I tried the suggestion.. While it fixes the self.channel NoneType issu=
e.. It creates another issue.<br>
> <br>
> Traceback (most recent call last):<br>
>=C2=A0 =C2=A0File "/usr/local/Cellar/python/3.7.1/Frameworks/Pytho=
n.framework/Versions/3.7/lib/python3.7/asyncio/events.py", line 88, in=
_run<br>
>=C2=A0 =C2=A0 =C2=A0self._context.run(self._callback, *self._args)<br>
>=C2=A0 =C2=A0File "/usr/local/lib/python3.7/site-packages/twisted/=
internet/defer.py", line 827, in adapt<br>
>=C2=A0 =C2=A0 =C2=A0adapt.actual.callback(extracted)<br>
>=C2=A0 =C2=A0File "/usr/local/lib/python3.7/site-packages/twisted/=
internet/defer.py", line 460, in callback<br>
>=C2=A0 =C2=A0 =C2=A0self._startRunCallbacks(result)<br>
>=C2=A0 =C2=A0File "/usr/local/lib/python3.7/site-packages/twisted/=
internet/defer.py", line 568, in _startRunCallbacks<br>
>=C2=A0 =C2=A0 =C2=A0self._runCallbacks()<br>
> --- <exception caught here> ---<br>
>=C2=A0 =C2=A0File "/usr/local/lib/python3.7/site-packages/twisted/=
internet/defer.py", line 654, in _runCallbacks<br>
>=C2=A0 =C2=A0 =C2=A0current.result =3D callback(current.result, *args, =
**kw)<br>
> ......<br>
>=C2=A0 =C2=A0 =C2=A0request.finish()<br>
>=C2=A0 =C2=A0File "/usr/local/lib/python3.7/site-packages/twisted/=
web/server.py", line 268, in finish<br>
>=C2=A0 =C2=A0 =C2=A0return http.Request.finish(self)<br>
>=C2=A0 =C2=A0File "/usr/local/lib/python3.7/site-packages/twisted/=
web/http.py", line 1071, in finish<br>
>=C2=A0 =C2=A0 =C2=A0"Request.finish called on a request after its =
connection was lost; "<br>
> builtins.RuntimeError: Request.finish called on a request after its co=
nnection was lost; use Request.notifyFinish to keep track of this.<br>
<br>
Oh, hrm.=C2=A0 The idea here is that any code that returns NOT_DONE_YET (i.=
e. does asynchronous work to generate a response) should also be tracking w=
hether it needs to call `.finish()` by watching a `.notifyFinish()` Deferre=
d.=C2=A0 I bet that there are plenty of resources in Twisted which don'=
t follow this rule, and we should fix those; but possibly we should also ma=
ke this error message less stern.=C2=A0 Do you have a minimal example?<br>
<br>
>=C2=A0 I have got some handle on the issue. I was wondering if you have=
any advise on how to debug the issue. <br>
> Somewhere in the codebase are async/await code (from asyncio world). H=
ence, when the connection is closed down by client, seems like those pendin=
g coroutines are lingering on.<br>
<br>
This, I have no idea about.=C2=A0 What tasks are you starting, when are you=
expecting them to get cleaned up, what are they blocking on, how do these =
interact with Twisted?=C2=A0 There are a couple dozen questions I'd hav=
e to know the answer to in order to even begin debugging this.=C2=A0 If you=
cancel all the outstanding tasks and look at their tracebacks when exiting=
it might give you more of a sense of where they're stuck...<br>
<br>
-g<br>
<br>
_______________________________________________<br>
Twisted-Python mailing list<br>
<a href=3D"mailto:[email protected]" target=3D"_blank">Twist=
[email protected]</a><br>
<a href=3D"https://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-pytho=
n" rel=3D"noreferrer" target=3D"_blank">https://twistedmatrix.com/cgi-bin/m=
ailman/listinfo/twisted-python</a><br>
</blockquote></div>
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