component.stop() should not return session.leave() result (if session exists)

[npeditto]

In component.py the stop() should do session.leave() and return the a future object if session exists (not return session.leave() result only).

Otherwise we are not able to call again the component.start(...) method after stop() method called.

[codecov-io]

Codecov Report

Merging #1075 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master    #1075   +/-   ##
=======================================
  Coverage   41.55%   41.55%           
=======================================
  Files          69       69           
  Lines       13197    13197           
  Branches     2205     2205           
=======================================
  Hits         5484     5484           
  Misses       7293     7293           
  Partials      420      420

Impacted Files	Coverage Δ
autobahn/wamp/component.py	38.93% <0%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 2645f1e...4ef9f1a. Read the comment docs.

[oberstet]

actually, looks good and merging (as I am pushing a release) --

[meejah]

I don't understand what problem you're trying to solve here? session.leave does return a future/deferred (that fires when the session actually closes). If you don't care about that, just ignore the return value from .stop()

[meejah]

(If you do care about waiting for the disconnect to actually happen there won't be any way to do that now)

[oberstet]

@meejah uups, yes, right .. we do want to return the deferred from leave. lack of sleep, too much hurry;)

[npeditto]

In a scenario where I call "component.start(loop)" after a "component.stop()" with autobahn v18.9.2 an application is able to reconnect. Through the latest version (18.10.1) where the component.py has been updated (in particular, _start() and stop() methods) this application is not able to reconnect to Crossbar.

In particular, the attribute "self._done_f" in "_start(...)" method is not reset to "None". I tried also another workaround: in stop() method I set "self._done_f" to "None" before the "return self._session.leave()". So this could be another solution.

[meejah]

Component already knows how to re-connect, you shouldn't have to call start() again (and _start is an internal method, you should only call .start() the public API). Can you show some example code about what you're trying to accomplish?

[npeditto]

I don't understand what problem you're trying to solve here? session.leave does return a future/deferred (that fires when the session actually closes). If you don't care about that, just ignore the return value from .stop()

Yes, I was wrong about future object return. Maybe the problem, that I described in the previous post, is related to the "self._done_f" attribute that is not set to "None" in stop() method.

[meejah]

Maybe, I'm not sure I ever anticipated someone calling .start() more than once. What are you trying to do..?

[npeditto]

Component already knows how to re-connect, you shouldn't have to call start() again (and _start is an internal method, you should only call .start() the public API). Can you show some example code about what you're trying to accomplish?

Yes of course. I used in my code the start() method (not _start()).

In autobahn 18.9.2 if I call
component.stop()
(because I need for my reasons to close the wamp connection)

and then call
component.start(loop)

my application was able to reconnect to Crossbar again.

[meejah]

(And yes, it's probably more-correct to reset _done_f to None at some point or at least make it an error to call .start() a second time if we really can't/won't support that ... but I do want to understand your use-case..)

So essentially you have a reason to want to disconnect your Component for some amount of time and then re-connect it..?

[npeditto]

(And yes, it's probably more-correct to reset _done_f to None at some point or at least make it an error to call .start() a second time

It should be fine to reset _done_f to None

So essentially you have a reason to want to disconnect your Component for some amount of time and then re-connect it..?

Yes, I need to disconnect my application and reconnect it. Resetting the _done_f before return session.leave() I will be able to do that again (as in 18.9.2 version).
So for me is very important to avoid to "make it an error to call .start() a second time".

[meejah]

I think the correct fix is probably for _done_f to be reset after the leave() deferred fires. So your application code then might look something like:

my_component.start(..)
# ...
await my_component.stop()
# ...
my_component.start(..)

[npeditto]

my_component.start(..)
# ...
await my_component.stop()
# ...
my_component.start(..)

Exactly that is my workflow.

I think the correct fix is probably for _done_f to be reset after the leave() deferred fires.

I agree! Should the _done_f reset be insert into the stop() method (in component.py)?

[meejah]

Probably what should be done is anywhere we .resolve() the _done_f it should be reset to None..? (but maybe only on _stopping). Might need more thought for the different cases.

[meejah]

Moving to a ticket: #1077