Hi Jean, Yeah, actually that is the example that I looked into and implemented my code. The issue I have is.. still some instances of interrupted responses are not trapped. Copying pasting my minimal implementation for your convinence def print_json_response(resp, request): request.write(json.dumps(resp)) request.close() 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 async def fetch_response(self, request): future = {} try: future = await some other async def.. which returns future except asyncio.CancelledError as e: print("Error..", e) return future def handle_cancel(failure, d): d.cancel() print(failure.getTraceback()) On Mon, Aug 5, 2019 at 2:21 PM Jean-Paul Calderone < exarkun@twistedmatrix.com> wrote:
On Mon, Aug 5, 2019 at 2:15 PM Waqar Khan <wk80333@gmail.com> wrote:
False alarm. Seems like there are some sneaky conditions when I get the error message. Like before, I use to get notifyFinish error everytime. Now, it seems that 6/10 times things are "clean" but then 4/10 times there are notifyFinish errors. Wondering on your suggestion. How do I ensure whether the notifyFinish error deferred has been fired or not. Could I have like a vanilla "HelloWorld" example? Thanks
You can find an example of this here - https://twistedmatrix.com/documents/current/web/howto/web-in-60/interrupted....
Jean-Paul
On Mon, Aug 5, 2019 at 2:24 AM Waqar Khan <wk80333@gmail.com> wrote:
Hi Glyph, I am not sure I understand.
Is there a method/variable in request which keeps a track whether notifyFinish has been fired.. So, I can do something like.
if not request.hasFiredNotifyFinish: request.finish() ??
I have sort of able to get around this issue.. though I can't put a finger on what actually worked. Here is what I did.. First change to 19.7rc01 version.. and just fix the channel issue.
Next self.fetch_response(request).. This is an async def.. So what I did was..
async def fetch_response(request): future = {} try: future = await some other async def.. which returns future except asyncio.CancelledError as e: print("Error..", e) return future
I basically ended up doing this everywhere where there is async/await. Next, I added this: d.addErrback(lambda failure: failure.trap(asyncio.CancelledError))
So.. now.. I don't see the notifyFinish error anymore. And I am bit terrified not to touch anything.. :-D
But, I want to try out your suggestion as that seems like a more solid way to handle the issue. But I am not sure I quite understand, how do I figure out whether notifyFinish has been called before calling finish?
On Mon, Aug 5, 2019 at 1:56 AM Glyph <glyph@twistedmatrix.com> wrote:
On Aug 4, 2019, at 9:04 PM, Waqar Khan <wk80333@gmail.com> wrote:
Ah yes.. That is true..
If I comment out request.finish() (Here is the doc which I tried to followed: https://twistedmatrix.com/documents/13.0.0/web/howto/web-in-60/interrupted.h... ) Then actually.. when I try to test out the code... (via curl or like doing requests.get .. to the URI).. it is just stuck..
Yep! This makes sense; if you don't call `.finish()` *at all* then your code will never tell the client that it's done.
But if you call `.finish()` *after notifyFinish() has fired* then you get that error.
If you change your code to only call `.finish()` if the deferred returned by notifyFinish() has not fired or failed yet, do you get the error? It's possible that you still do, in which case, there's a bug in Twisted that needs to be fixed.
I do want to convey my thanks for the help. Really appreciate it.
Thanks for using Twisted :) -g
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