automatic restart when Python code changes

[Martijn Faassen]

We need to investigate automatically restarting Grok whenever a .py file changes. Other web frameworks do this by default. I'd suggest Grok also enables this by default, with perhaps an 'off' button (and other configuration of this behavior?) in our UI somewhere.

To implement this, we need to look at what TurboGears/Pylons/Django/Paste are doing and hopefully well be able to reuse code from one of them.

[Kevin Teague (kevin-bud)]

Here is the Django implementation (which was mostly taken from CherryPy), which just stats files every second in a seperate thread and causes a restart if a file has been modified:

http://code.djangoproject.com/browser/django/trunk/django/utils/autoreload.py

[Philipp von Weitershausen (philikon)]

The 'paster serve' command from PasteDeploy also has something like
this built-in. I've used it in the past and it works nicely with Grok
when Grok is deployed as a WSGI app. It doesn't pick up modified ZCML
files, but then Grok doesn't really need you to modify those in the
first place.

[Chris McDonough (chrism-plope)]

I'd suggest running Grok via "paster serve" out of the box by default as a WSGI app. There's no need to reinvent or even cut-and-paste any wheels here.

[Philipp von Weitershausen (philikon)]

On 7 Apr 2008, at 16:15 , Chris McDonough wrote:
> I'd suggest running Grok via "paster serve" out of the box by
> default as
> a WSGI app. There's no need to reinvent or even cut-and-paste any
> wheels here.

Exactly

[Peter Bengtsson (mail-peterbe)]

How far are we with the paster serve progress? I've got an immediate solution that works that uses inotify if available otherwise works similar to django. I can push my hack into a formal patch with some help but if paster serve is going to replace the current runner within the nearest months I might as well take it easy.

My solution is at least very unintrusive and is able to distinguise .pt files that define METAL macros since changing these requires a zope restart.

[Michael Haubenwallner (d2m)]

There is a branch at http://svn.zope.org/grokproject/branches/d2m-dual-startup/
to support both startup modes (zopectl and paster serve).

Autorestart is available through paster like:

  bin/paster serve --reload etc/debug.ini

[Martijn Faassen (faassen)]

Brandon, looks like we got support for this now. I think we need to better document this in the tutorial though: Michael's "bin/paster serve --reload etc/debug.ini" needs to be mentioned prominently otherwise nobody will know. Feel free to reassign to Michael (d2m) if you can coordinate this with him too.

[Brandon Rhodes (brandon-rhodes)]

Martijn —

I have confirmed that this command indeed works! Per the comments above, do we want to abandon the little "g-ctl" and "g-debug" commands that currently hide paster from the developer? They don't even have useful help:

$ bin/g-ctl --help
No help available.
$ bin/g-debug --help
------
2009-01-19T16:01:58 WARNING root Developer mode is enabled: this is a security risk and should NOT be enabled on production servers. Developer mode can be turned off in etc/zope.conf
Welcome to the interactive debug prompt.
The 'root' variable contains the ZODB root folder.
The 'app' variable contains the Debugger, 'app.publish(path)' simulates a request.
>>>

And it's not clear to me what we're gaining by hiding the simple "paster serve etc/deploy.ini" command when they're going to have to use it anyway to get file reloading. Plus it makes us "look incompatible" and "look non-WSGI", in my opinion, when users are running a dinky little command whose name they do not recognize from the other web frameworks they use.

Also: when I document (maybe this evening, but probably later in the week), we need to mention that ---reload currently does *not* detect new files that need to be Grokked; it only reloads when it sees an existing file change.

[Uli Fouquet (uli-gnufix)]

I personally like the debugger (``g-debug`` in your example) pretty much and use it regularly, but maybe I just missed how to archive the same functionality with bin/paster.

[Michael Haubenwallner (d2m)]

described the --reload option in more detail in doc/tutorial.rst