[Twisted-Python] giving a reason when adding a timeout

[Adi Roiban]

On Wed, 13 Mar 2019 at 16:07, Chris Withers <chris at withers.org> wrote:
>
> >> Unless I'm missing something, Deferred.addTimeout is really unhelpful in
> >> terms on providing context about *what* timed out.
> >> TimeoutError(<some number>, 'Deferred') just isn't that useful.
> >>
> >> How come addTimeout doesn't let you specify a textual reason, or
> >> otherwise provide some context about the timeout?
> >>
> >> Am I missing something obvious here?
> >
> > I don't know what kind of context do you need :)
>
> foo.addTimeout(myTimeout, reactor, message='never heard back')
>
> > You can add your own errback and add your extra error handling there.
>
> What's the must succinct way to get the above by adding an errback?
>

That is subjective :)
You can try something like this.

def eb_timeoutLog(failure, message):
    failure.trap(TimeoutError)
    print(message)

deferred = someJob()
deferred.addTimeout(10, reactor)
deferred.addErrback(eb_timeoutLog, message='never heard back')

or like this

def eb_timeoutLog(failure, message):
    failure.trap(TimeoutError)
    print(message)

def add_timeout(deferred, timeout, message):
    deferred.addTimeout(10, reactor)
    deferred.addErrback(eb_timeoutLog, message)

deferred = someJob()
add_timeout(deferred, message='never heard back')


> > There is also onTimeoutCancel argument.
>
> Pretty clunky to write a whole function for either this or the errback
> just to change the useless 'Deferred' string in the current
> implementation with something useful.

For production code I add errbacks anyway.
The errback catches various error conditions and does more than just
printing a text.
I am not missing anything here :)

> > If there is anything missing from the API, feel free to send a pull
> > request in GitHub.
>
> What's the likely turn around time from me submitting a PR to when it
> ends up in a released version of Twisted that I can use?

I don't you the answer to that question.

If this is something that you want to be improved, my suggestion is to
give it a try.

The whole Twisted was created by people who had an issue and were
willing to effort required to share the solution with the rest of the
world :)

> Chris



-- 
Adi Roiban