Routes planning and the road to Routes 2.0

Posted by ben Wed, 29 Aug 2007 17:04:24 GMT

Routes has been a wonderfully successful project of mine as its used not just in Pylons but quite a few other small WSGI apps. It’s even been integrated as a CherryPy URL dispatching option for those using TurboGears 1.x or plain CherryPy. It’s come a long way since 1.0 and has diverged on quite a few fronts from the Rails version that it was originally duplicating in functionality, which has me thinking that perhaps its time to consider 2.0 and what that will mean.

First, I think there’s quite a few behaviors that don’t make sense and probably never have. The Route minimizing functionality sounds neat and fulfills the Rails ideal of ‘keeping urls pretty’ yet suffers from a fundamental flaw… they result in multiple valid URL’s for the same page. James Tauber covers some of the implications of this in addition to the issue with relative URL’s not working right either. The example he cites is even worse for Routes since Routes can easily result in multiple URL’s mapping to the same controller action.

Routes 2.0

To solve the multiple URL issue, and also address some Named Routes confusion that recently hit the Pylons mailing list, Routes 2.0 will do a few things differently than Routes 1.X. Many things will be significantly more explicit and more predictable as a result. In addition, I want to add more functionality so that Routes can be the end-all of URL generation in addition to URL dispatching, even for use purely generating links conditionally that aren’t even used for URL dispatching.

Some of the key changes planned for Routes 2.0:

  • Routes recognition and generation will always be explicit Currently, there’s an explicit option that removes the keyword controller/action/id defaults, 2.0 will not have these implicit defaults.
  • Defaults don’t cause minimization Defaults just mean they’ll be used, they won’t result in Route minimization which increases the amount of URL’s that end up matching to a single controller action.
  • Trailing slashes shouldn’t be an issue Without routes being minimized, a route such as ’/home/index’ will always be ’/home/index’ instead of being minimized to /home/. This will resolve the trailing slash issue.
  • Named Routes will always use the route named A named route currently just means that the defaults for that route will be used during route generation. This currently can cause confusion because people believe that the named route actually forces that route to be used during generation.
  • Generation-only routes A new option, which will result in routes that are used purely for generation. This option will likely be used primarily for static resources which may be on other servers, or may need the domain rotated so that the browser can do parallel resource loading. For example, one would be able to provide a list of domains to be used, and the generated links will rotate as desired on the page to split page resources over multiple domains.
  • Redirect routes Sometimes, (especially when replacing legacy apps), its desirable to slowly migrate URL scheme’s from the old to the new rather. While URL’s should never change, sometimes the system being replaced has horrid URL’s that violate all URL recommendations. Being able to provide a smooth migration path from the old URL’s to the new ones is handy, and permanent redirects are respected by many search crawlers as well.

Migration and Compatibility

Routes 1.8 will include options to turn on behavior that will be the default in Routes 2.0, and if you like how Routes 1.X works there’s no need to worry, it will still be maintained for the foreseeable future. It’s currently extremely stable, and has a massive unit test suite to ensure it operates as designed.

Add Your Desired Feature Here

What other features are Routes users currently looking for?

Posted in ,  | 13 comments

Routes planning and the road to Routes 2.0

Posted by ben Wed, 29 Aug 2007 17:04:24 GMT

Routes has been a wonderfully successful project of mine as its used not just in Pylons but quite a few other small WSGI apps. It’s even been integrated as a CherryPy URL dispatching option for those using TurboGears 1.x or plain CherryPy. It’s come a long way since 1.0 and has diverged on quite a few fronts from the Rails version that it was originally duplicating in functionality, which has me thinking that perhaps its time to consider 2.0 and what that will mean.

First, I think there’s quite a few behaviors that don’t make sense and probably never have. The Route minimizing functionality sounds neat and fulfills the Rails ideal of ‘keeping urls pretty’ yet suffers from a fundamental flaw… they result in multiple valid URL’s for the same page. James Tauber covers some of the implications of this in addition to the issue with relative URL’s not working right either. The example he cites is even worse for Routes since Routes can easily result in multiple URL’s mapping to the same controller action.

Routes 2.0

To solve the multiple URL issue, and also address some Named Routes confusion that recently hit the Pylons mailing list, Routes 2.0 will do a few things differently than Routes 1.X. Many things will be significantly more explicit and more predictable as a result. In addition, I want to add more functionality so that Routes can be the end-all of URL generation in addition to URL dispatching, even for use purely generating links conditionally that aren’t even used for URL dispatching.

Some of the key changes planned for Routes 2.0:

  • Routes recognition and generation will always be explicit Currently, there’s an explicit option that removes the keyword controller/action/id defaults, 2.0 will not have these implicit defaults.
  • Defaults don’t cause minimization Defaults just mean they’ll be used, they won’t result in Route minimization which increases the amount of URL’s that end up matching to a single controller action.
  • Trailing slashes shouldn’t be an issue Without routes being minimized, a route such as ’/home/index’ will always be ’/home/index’ instead of being minimized to /home/. This will resolve the trailing slash issue.
  • Named Routes will always use the route named A named route currently just means that the defaults for that route will be used during route generation. This currently can cause confusion because people believe that the named route actually forces that route to be used during generation.
  • Generation-only routes A new option, which will result in routes that are used purely for generation. This option will likely be used primarily for static resources which may be on other servers, or may need the domain rotated so that the browser can do parallel resource loading. For example, one would be able to provide a list of domains to be used, and the generated links will rotate as desired on the page to split page resources over multiple domains.
  • Redirect routes Sometimes, (especially when replacing legacy apps), its desirable to slowly migrate URL scheme’s from the old to the new rather. While URL’s should never change, sometimes the system being replaced has horrid URL’s that violate all URL recommendations. Being able to provide a smooth migration path from the old URL’s to the new ones is handy, and permanent redirects are respected by many search crawlers as well.

Migration and Compatibility

Routes 1.8 will include options to turn on behavior that will be the default in Routes 2.0, and if you like how Routes 1.X works there’s no need to worry, it will still be maintained for the foreseeable future. It’s currently extremely stable, and has a massive unit test suite to ensure it operates as designed.

Add Your Desired Feature Here

What other features are Routes users currently looking for?

Posted in ,  | 13 comments

Routes functional conditions and WSGI Middleware

Posted by ben Sun, 19 Aug 2007 04:38:51 GMT

Sometimes, it amazes me whats possible fully utilizing WSGI middleware in an application stack. While it likely isn’t something totally unique to the framework, the relative ease with which it can be done still sometimes gets me to grin.

Tonight, a Pylons user on the IRC channel (irc.freenode.net, #pylons) asked if it was possible to get a URL laid out so that /s/SOMETHING would map into their ’s’ controller, with the second part passed in as a variable. That alone is pretty easy, however the additional requirement was that the controller action would change depending on the user’s “type”.

There’s two ways to deal with this, the first of which is the only possible way in many frameworks. Have every request to the URL map to a single function, and in that function load up the session and call the appropriate function to handle the request based on their user type. This way works fine in Pylons too, but thanks to Routes and WSGI middleware we have another option.

Routes has a lot of capabilities to it, there’s been numerous additions to the Python implementation that the Rails version is not capable of. One of them is the ability to alter the resulting URL match dictionary in various conditional functions. To toggle the controller action used, we’ll be using the ability to pass in a function to Routes conditions that can alter the resulting match.

This condition checking function has full access to the WSGI environ so if you wanted to restrict a specific controller/action combination to people referred from Slashdot, no problem! You can carefully fine-tune the conditions required for dispatch at the same place you define your URL resolution.

Since Pylons uses Beaker for session handling via WSGI middleware, the session object will already be available when our Pylons app gets called. Beaker loads the user session into environ['beaker.session']. Given this knowledge, we can write a conditional function for use with Routes like so:


def check_user(environ, result):
    session = environ['beaker.session']
    user_type = session.get('type')
    if not user_type:
        result['action'] = 'index'
    elif user_type == 'admin':
        result['action'] = 'view_action'
    else:
        result['action'] = 'not_logged_in'
    return True
map.connect('s/:domain', controller='s', conditions=dict(function=check_user))

Viola! Now Routes will run the function provided to see if it returns True before accepting that as a valid match. In the process, the action used will be set as desired. I’ve always thought a good sign something is well designed is when people can use it in ways you didn’t originally anticipate. If that’s the criteria, I think Routes succeeds and then some.

Disclaimer: Yes, I wrote Routes, and a good chunk of Beaker and Pylons, so I might be biased and tooting my own horn. :)

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Routes functional conditions and WSGI Middleware

Posted by ben Sun, 19 Aug 2007 04:38:51 GMT

Sometimes, it amazes me whats possible fully utilizing WSGI middleware in an application stack. While it likely isn’t something totally unique to the framework, the relative ease with which it can be done still sometimes gets me to grin.

Tonight, a Pylons user on the IRC channel (irc.freenode.net, #pylons) asked if it was possible to get a URL laid out so that /s/SOMETHING would map into their ’s’ controller, with the second part passed in as a variable. That alone is pretty easy, however the additional requirement was that the controller action would change depending on the user’s “type”.

There’s two ways to deal with this, the first of which is the only possible way in many frameworks. Have every request to the URL map to a single function, and in that function load up the session and call the appropriate function to handle the request based on their user type. This way works fine in Pylons too, but thanks to Routes and WSGI middleware we have another option.

Routes has a lot of capabilities to it, there’s been numerous additions to the Python implementation that the Rails version is not capable of. One of them is the ability to alter the resulting URL match dictionary in various conditional functions. To toggle the controller action used, we’ll be using the ability to pass in a function to Routes conditions that can alter the resulting match.

This condition checking function has full access to the WSGI environ so if you wanted to restrict a specific controller/action combination to people referred from Slashdot, no problem! You can carefully fine-tune the conditions required for dispatch at the same place you define your URL resolution.

Since Pylons uses Beaker for session handling via WSGI middleware, the session object will already be available when our Pylons app gets called. Beaker loads the user session into environ['beaker.session']. Given this knowledge, we can write a conditional function for use with Routes like so:


def check_user(environ, result):
    session = environ['beaker.session']
    user_type = session.get('type')
    if not user_type:
        result['action'] = 'index'
    elif user_type == 'admin':
        result['action'] = 'view_action'
    else:
        result['action'] = 'not_logged_in'
    return True
map.connect('s/:domain', controller='s', conditions=dict(function=check_user))

Viola! Now Routes will run the function provided to see if it returns True before accepting that as a valid match. In the process, the action used will be set as desired. I’ve always thought a good sign something is well designed is when people can use it in ways you didn’t originally anticipate. If that’s the criteria, I think Routes succeeds and then some.

Disclaimer: Yes, I wrote Routes, and a good chunk of Beaker and Pylons, so I might be biased and tooting my own horn. :)

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Routes 1.4 Release and Web Services

Posted by ben Wed, 02 Aug 2006 17:26:00 GMT

This is slightly old as Routes 1.4 was released about a week and a half ago, but I thought it deserved some attention. There were a handful of fixes and some slightly major feature enhancements in 1.4.

From the changelog:

  • Fixed bug with map.resource related to member methods, found in Rails version.
  • Fixed bug with map.resource member methods not requiring a member id.
  • Fixed bug related to handling keyword argument controller.
  • Added map.resource command which can automatically generate a batch of routes intended to be used in a REST-ful manner by a web framework.
  • Added URL generation handling for a ‘method’ argument. If ‘method’ is specified, it is not dropped and will be changed to ‘_method’ for use by the framework.
  • Added conditions option to map.connect. Accepts a dict with optional keyword args ‘method’ or ‘function’. Method is a list of HTTP methods that are valid for the route. Function is a function that will be called with environ, matchdict where matchdict is the dict created by the URL match.
  • Fixed redirect_to function for using absolute URL’s. redirect_to now passes all args to url_for, then passes the resulting URL to the redirect function. Reported by climbus.

Web Resources

The map.resource command is based directly off the Simply Restful Rails plugin which adds support for various verb-oriented controller actions in a RESTful service style approach. The Simply Restful layout is more or less the exact service style laid out in the Atom Publishing Protocol.

It’s a great approach and it also meant providing a few other features to Routes that I hadn’t implemented previously, the most important being able to limit matching of a URL based on the HTTP method used. This is present in the new conditions clause for a Route: 

map.connect('user/:id', controller='user', action='edit', 
    conditions={'method', ['GET', 'HEAD']})
map.connect('user/:id', controller='user', action='update',
    conditions={'method', ['PUT']})
The conditions clause can also accept your own function should you want to restrict the route to matching based off some other criteria (sub-domain, IP address, etc). 

def stop_comcast(environ, match):
    if 'comcast.net' in environ['REMOTE_HOST']:
        return False
    return True

map.connect(':controller/:action/:id', conditions={'function':stop_comcast})

David Heinemeier Hansson recently posted an entry about Resources on Rails discussing how important web services are. The other key point was to make it easier to write controllers that could not only give you easy browser access to your resources, but provide a web service API as well.

The two snippets shown above give you an edit and update capability that restricts matching based off the HTTP method (verb). Writing a huge mess of those for the rest of the functions needed for a full web service API like Atom is a bit of busy-body work, so in the opinionated style of Rails a single command wraps up the whole thing. In Routes it looks like this: 

map.resource('user')

That will make the two routes at the top of this entry in addition to routes that handle PUT, and DELETE. It maps them out to a set of actions in the controller, and provides the capability to easily add more methods for specific verbs.

The map.resource command is still getting tuned up, and we’re integrating the additional functionality it provides back into Pylons as well. Josh Triplett also wrote some Python code that will parse HTTP Accept headers fully so that we can add some nice functionality to use in the controller to return the appropriate data given what the client is expecting (HTML, XML, JSON, etc.)

If you’re using a Python web framework that doesn’t use Routes… maybe its time to put a request in. :)

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