questions for tornado.routing

[HENG]

Hi:

I'm notice tornado has new module named tornado.routing and happy to have a test

app1 = Application([
    (r"/app1/handler", Handler1),
    # other handlers ...
])

app2 = Application([
    (r"/app2/handler", Handler2),
    # other handlers ...
])

router = RuleRouter([
    Rule(PathMatches("/app1.*"), app1),
    Rule(PathMatches("/app2.*"), app2)
])

server = HTTPServer(router)

BUT it can not run ....

It will thorow an error as follow:

[E 170403 03:26:12 http1connection:54] Uncaught exception 
Traceback (most recent call last): 
File "/home/vagrant/www/local/lib/python2.7/site-packages/tornado/http1connection.py", line 238, in _read_message
delegate.finish() 
File "/home/vagrant/www/local/lib/python2.7/site-packages/tornado/httpserver.py", line 314, in finish 
self.delegate.finish() 
File "/home/vagrant/www/local/lib/python2.7/site-packages/tornado/routing.py", line 251, in finish 
self.delegate.finish() 
File "/home/vagrant/www/local/lib/python2.7/site-packages/tornado/httpserver.py", line 229, in finish 
self.request_callback(self.request) 
TypeError: __init__() takes exactly 1 argument (2 given)

I use Tornado repo master code, just use:   pip install git+https://github.com/tornadoweb/tornado.git

How to use tornado.routing???? Do we have some document that more details???

Thx

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Heng
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[Сумин Андрей]

Hi,

Thank you for your feedback!

Could you please show the complete code that throws this exception?

I've created a gist with a simple demonstration here: https://gist.github.com/SuminAndrew/1d66c21a42478a7a9f53174d472a1a77

It uses an example from the docs, adding missing imports and handler definitions.

Could you also check it out?

Best regards,

Andrew.

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[HENG]

Thanks for sumin.andrew!

I do not have Linux at home so just use my wife windows to has a test.

​

That is an error, but I get a normal response in Chrome

That is a little strange~

[HENG]

I ask for help because I forgot to initialize the `tornado.web.Application` class

1.as normal, we rewrite the Application class as follow:

class MyApplication(tornado.web.Application):

    def __init__(self):

        pass # do something

        super(.....).__init__(handlers=[], **settings)

Then, we use `MyApplication` like this:

router = RuleRouter([

    Rule(PathMatches("/app1.*"), MyApplication),  # here Application class has not init as instance!!!!

])

server = HTTPServer(router)

This code will throw error because the Application has NOT init, just as follow:

[E 170403 03:26:12 http1connection:54] Uncaught exception 

Traceback (most recent call last): 

File "/home/vagrant/www/local/lib/python2.7/site-packages/tornado/http1connection.py", line 238, in _read_message

delegate.finish() 

File "/home/vagrant/www/local/lib/python2.7/site-packages/tornado/httpserver.py", line 314, in finish 

self.delegate.finish() 

File "/home/vagrant/www/local/lib/python2.7/site-packages/tornado/routing.py", line 251, in finish 

self.delegate.finish() 

File "/home/vagrant/www/local/lib/python2.7/site-packages/tornado/httpserver.py", line 229, in finish 

self.request_callback(self.request) 

TypeError: __init__() takes exactly 1 argument (2 given)

Read the source code in  https://github.com/tornadoweb/tornado/blob/master/tornado/routing.py#L393 

As the truth, `tornado.routing.Rule` target can access `tornado.web.Application` instance, 

But the 4.5b1 document just consider HTTPServerConnectionDelegate and forgot to remind that `tornado.web.Application` is a sub-class of HTTPServerConnectionDelegate

And

I follow tornado from it was release from friendfeed

It'code was simple and beatiful in v1.0

now Tornado was stronger and better than before, but I feel heavy to follow the code change, even I use day by day

Maybe this is the software rule: the more it have, the heavy code they are

Just as joke to have fun

Thanks

[Сумин Андрей]

Hi,

This happens because Chrome may generate other requests alongside with your request for "/app1/handler", for example, a request for favicon.

This path is not mapped in the RuleRouter, so the router returns None when it tries to find a suitable handler. This results in an error that you see in your logs (and the original request succeeds).

If you use low-level routing mechanisms like this, you're on your own with handling such situations.

To handle this this in real code, you can add one more rule:

Rule(PathMatches(".*"), _Some404Handler_)

with a handler of your choosing.

[HENG]

Thanks for reply! 

[Сумин Андрей]

Hi again!

Let's look at the code that you provided:

router = RuleRouter([

    Rule(PathMatches("/app1.*"), MyApplication),  # here Application class has not init as instance!!!!

])

server = HTTPServer(router)

This code is broken as you correctly pointed out, but neveretheless due to Python's dynamic nature it reveals its flow only at runtime.

Moreover, MyApplication may still be a valid routing target, because any class object is callable and RuleRouter accepts callables as routing targets: https://github.com/tornadoweb/tornado/blob/master/tornado/routing.py#L346

So the exception is raised only when we actually try to use this target as the contract dictates us (https://github.com/tornadoweb/tornado/blob/master/tornado/httpserver.py#L229), calling __init__(self, request).

But your MyApplication.__init__ signature looks like __init__(self) — and that is exactly what you see in the error message.

The docs actually contain the information about Application implementing Router/HTTPServerConnectionDelegate here: https://github.com/tornadoweb/tornado/blob/master/tornado/routing.py#L17

And I agree with you — unfortunately sometimes you must pay for flexibility, especially when breaking backwards compatibility is not an option.

[HENG]

Thanks for the details. Thanks!