Re: Error "signal only works in main thread"

Hello Max,

> thanks for your answer! I implemented a plugin for the optimization 
> routines, but it still results in the same error. :/ Are you sure
> plugins run on the main thread?
> 
> Please take a look at the code - did I do anything wrong?
> https://gist.github.com/anonymous/d955db89c8381d052653


I was wrong about the assumption of the plugins and the main thread.
You implemented correctly what I suggested.

But don't despair! I just hacked away a nifty class that can help you.

The full example is in this gist:

https://gist.github.com/cyraxjoe/93bedb7d942e75ac44f7

But I'll copy/paste the relevant class and decorator:


class MainExecutor:
    """Wrap a callable to ensure that the execution takes place on the
    MainThread based on the cherrypy.engine and the 'main' channel.

    For example:

    >>> def sample(arg): return "foo {}".format(arg)
    ...
    >>> mexec = MainExecutor(sample)
    >>> mexec("bar")
    'foo bar'
    >>> mexec("test")
    'foo test'
    """

    def __init__(self, func, bus=cp.engine):
        self.func = func
        self.bus = bus

    def __call__(self, *args, **kwargs):
        results = []
        done_event = threading.Event()
        executable = functools.partial(
            self._execute, results, done_event, *args, **kwargs)
        self.bus.subscribe('main', executable)
        done_event.wait()
        self.bus.unsubscribe('main', executable)
        success, rsp = results
        if success:
            return rsp
        else:
            raise rsp

    def _execute(self, response, done_event, *args, **kwargs):
        try:
            result = self.func(*args, **kwargs)
        except Exception as e:
            response.append(False)
            response.append(e)
        else:
            response.append(True)
            response.append(result)
        finally:
            done_event.set()


def in_main_thread(func):
    """Pretty interface to use the MainExecutor class
    as a decorator and not have the CamelCase on a decorator.
    """
    return MainExecutor(func)


Cheers,
-- 
Rivera²

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