ReloadWSGI 0.3

Replacement for ‘paster serve –reload config.ini’.

Reload a WSGI application on source change. Keep the old code alive when the change has syntax errors. Never close the socket, never refuse a connection.

As of version 0.3, ReloadWSGI also supports reloading a server specified in the config file. This is appropriate for wsgi servers such as mongrel2_wsgi which are able to support two concurrent instances without stepping on each other’s network connection. Once ReloadWSGI confirms the second server can load without throwing e.g. a syntax error, the original server quits and Mongrel2’s automatic load balancing sends requests to the newer instance.

PID 4197 notifies us of a change in quux.py

quux.py changed; reloading...
{'status': 'changed', 'pid': 4197}

Oh no! We accidentally typed “foobar” instead of “import foobar”!

Process Process-4:
Traceback (most recent call last):
 ...
  File "quux.py", line 6, in <module>
    foobar
NameError: name 'foobar' is not defined

Can we visit our site? YES!:

127.0.0.1 - - [03/Mar/2010 09:41:52] "GET /orders HTTP/1.1" 200 2345

PID 4197 notifies us of /another/ change in quux.py

quux.py changed; reloading...
{'status': 'changed', 'pid': 4197}

We’ve fixed our problem. Once the new process loads, the old process quits silently

09:42:39,789 DEBUG [quux.run] App started.
{'status': 'loaded', 'pid': 4354}