[PEAK] Stopping PEAK application on SIGINT

Fri Oct 2 19:07:25 EDT 2015

The issue is that ISelector is a subclass of ISignalSource, and so
another Selector is created instead of the SignalSource singleton.  I
don't really have a good way to fix this right now, but as a
workaround you could monkeypatch to set Selector.sigsrc to
io_events.SignalEvents and see how that works.  (In truth, I think the
real problem may be that PEAK's signals support was never tested in
conjunction with Twisted, and IIRC, the signals support was only
half-baked to begin with when most work on PEAK ceased 10-11 years
ago.)

On Fri, Oct 2, 2015 at 6:51 AM, Alexey Smishlayev <alexey at xtech2.lv> wrote:
> Hello!
>
> I tried using pdb today, to some degree of success. Turns out that
> eventLoop.sigsrc attribute gets an instance of
> "peak.events.twisted_support.Selector". eventLoop.signals attribute is
> "binding.Delegate('sigsrc')", so it gets resolved to
> "peak.events.twisted_support.Selector.signals", which is
> "binding.Delegate('sigsrc')" - that's where recursion appears.
>
> I've gathered some evidence using pdb:
>>
>> /Library/Python/2.7/site-packages/peak/config/config_components.py(398)lookup()
> -> for value in iterValues(component, configKey):
> (Pdb) component
> <peak.config.config_components.ServiceArea object at 0x108ba3390>
> (Pdb) configKey
> config.MultiKey(<class 'peak.binding.interfaces.IComponentFactory'>, <class
> 'peak.events.interfaces.ISignalSource'>)
> (Pdb) [x for x in iterValues(component, configKey)]
> [<class 'peak.events.twisted_support.Selector'>, <class
> 'peak.events.io_events.SignalEvents'>]
>
> --
>
>>
>> /Library/Python/2.7/site-packages/peak/config/config_components.py(384)iterValues()
> -> value = gcd(forObj, configKey)
> (Pdb) forObj
> <peak.config.config_components.ServiceArea object at 0x108ba3390>
> (Pdb) configKey
> config.MultiKey(<class 'peak.binding.interfaces.IComponentFactory'>, <class
> 'peak.events.interfaces.ISignalSource'>)
> (Pdb) gcd
> <bound method ServiceArea._getConfigData of
> <peak.config.config_components.ServiceArea object at 0x108ba3390>>
> (Pdb) gcd(forObj, configKey)
> <class 'peak.events.twisted_support.Selector'>
>
> --
>
>>
>> /Library/Python/2.7/site-packages/peak/config/config_components.py(593)_getConfigData()
> -> value = rule.get()(self, configKey, forObj)
> (Pdb) rule.get()
> <function f at 0x1094bfcf8>
> (Pdb) rule.get()(self, configKey, forObj)
> <class 'peak.events.twisted_support.Selector'>
>
> Unfortunately, my efforts stop here. I have no idea where from this function
> f appeared in configuration rules, but it creates Selector instance, which
> messes up the lookup.
> From peak.ini: " peak.events.interfaces.ISignalSource =
> io_events.SignalEvents"
> I tried grepping "ISignalSource" in my project's directory, but this gives
> no results.
>
>
> Regards,
> Alexey
>
>
>
> On 30/09/15 02:12, PJ Eby wrote:
>
> The failure is in trying to retrieve the `signals()` method from the
> ISignalSource, which should be the io_events.SignalSource singleton.
> What I don't understand is why it's recursing on the attempt to
> retrieve the signals attribute.  Specifically, it seems as though this
> should only be able to happen if trying to load the 'sigsrc' attribute
> results in an attempt to load the 'signals' attribute.  I would
> suggest stepping through with the debugger from line 66 of
> scheduler.py and see if you can tell what's happening there.
>
> On Tue, Sep 29, 2015 at 5:56 PM, Alexey Smishlayev <alexey at xtech2.lv> wrote:
>
> Hello, Phillip!
>
> I use binding.Obtain() on "peak.running.interfaces.IMainLoop", which seem to
> be instantiating as "peak.running.scheduler.MainLoop" and the
> "peak.events.interfaces.IEventLoop" is bound to
> "peak.events.twisted_support.EventLoop". Did not go that far, looked at the
> PEAK default event loop and couldn't figure out what's wrong (without
> investgating links in the project's .ini file).
>
> Does that mean I cannot use stopOnSignals with the Twisted event loop? Do I
> have to implement that method? I believe, it's used because Twisted handles
> TCP communications for us.
>
>
> Best regards,
> Alexey Smishlayev
>
>
> On 30/09/15 00:27, PJ Eby wrote:
>
> Which event loop are you using?  Twisted, the PEAK default, or
> something else?  The issue here appears to be that the eventLoop
> property of the MainLoop instance lacks a `signals()` method -- which
> would seem to mean it doesn't fully implement IEventLoop or is the
> wrong type of object to start with.
>
> On Tue, Sep 29, 2015 at 8:06 AM, Alexey Smishlayev <alexey at xtech2.lv> wrote:
>
> Good day everyone!
> I would like my PEAK application to stop on ^C or SIGINT. Currently, in that
> case I get an output something like
>
> 29.09.2015 14:56:48.179 [DEBUG] Connect.twisted Unexpected error in main
> loop.
> 29.09.2015 14:56:48.190 [ERROR] Connect.twisted Traceback (most recent
> call last):
> 29.09.2015 14:56:48.190 [ERROR]   File
> "/Users/alexey/xtech2/tester/build/lib/ank/BBS/CommandBase.py", line 38, in
> run
> 29.09.2015 14:56:48.190 [ERROR]     self.mainLoop.run()
> 29.09.2015 14:56:48.190 [ERROR]   File
> "/Library/Python/2.7/site-packages/peak/running/scheduler.py", line 78, in
> run
> 29.09.2015 14:56:48.190 [ERROR]     return
> self.eventLoop.runUntil(self.exitCode,True,idle=self.sleep)[0]
> 29.09.2015 14:56:48.190 [ERROR]   File
> "/Library/Python/2.7/site-packages/peak/events/twisted_support.py", line
> 186, in runUntil
> 29.09.2015 14:56:48.190 [ERROR]     self.reactor.run(False)
> 29.09.2015 14:56:48.190 [ERROR]   File
> "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/twisted/internet/base.py",
> line 1192, in run
> 29.09.2015 14:56:48.190 [ERROR]     self.mainLoop()
> 29.09.2015 14:56:48.190 [ERROR] --- <exception caught here> ---
> 29.09.2015 14:56:48.190 [ERROR]   File
> "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/twisted/internet/base.py",
> line 1204, in mainLoop
> 29.09.2015 14:56:48.190 [ERROR]     self.doIteration(t)
> 29.09.2015 14:56:48.190 [ERROR]   File
> "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/twisted/internet/selectreactor.py",
> line 105, in doSelect
> 29.09.2015 14:56:48.190 [ERROR]     [], timeout)
> 29.09.2015 14:56:48.190 [ERROR] exceptions.KeyboardInterrupt:
>
> in the log file. In CommandBase.py attribute self.mainloop is defined as
>
> from peak.api import binding
> from peak.running import commands, interfaces
> class CommandBase(commands.EventDriven):
>     mainLoop = binding.Obtain(interfaces.IMainLoop)
>     ...
>
> If I set "peak.running.mainLoop.stopOnSignals" in my project's .ini file to
> anything else except empty tuple, on the application's startup I get the
> following error (I tried "stopOnSignals = ('SIGINT',)")
>
> Traceback (most recent call last):
>   File "../ank/BBS/Assembler.py", line 370, in run
>     _exitCode = _root.run()
>   File "/Library/Python/2.7/site-packages/peak/running/commands.py", line
> 229, in run
>     return self._run() or 0
>   File "/Library/Python/2.7/site-packages/peak/running/commands.py", line
> 509, in _run
>     return self.invoke()
>   File "/Users/alexey/xtech2/tester/build/lib/ank/BBS/CommandBase.py",
> line 38, in run
>     self.mainLoop.run()
>   File "/Library/Python/2.7/site-packages/peak/running/scheduler.py", line
> 66, in run
>     handler = self.eventLoop.signals(*self.stopOnSignals)
>   File "_once.pyx", line 112, in _once.BaseDescriptor.__get__
>   File "_once.pyx", line 100, in _once.__get__
>   File "/Library/Python/2.7/site-packages/peak/binding/components.py",
> line 682, in delegate
>     return getattr(getattr(s,delegateAttr),a)
>   File "_once.pyx", line 112, in _once.BaseDescriptor.__get__
>   File "_once.pyx", line 100, in _once.__get__
>   File "/Library/Python/2.7/site-packages/peak/binding/components.py",
> line 682, in delegate
>     return getattr(getattr(s,delegateAttr),a)
>   File "_once.pyx", line 88, in _once.BaseDescriptor.__get__
> AttributeError: ('Recursive attempt to compute attribute', 'signals')
>
> How do I do everything correctly?
>
>
> Best regards,
> Alexey Smishlayev
>
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