python 在Heroku上关闭django的中间件。见http://stackoverflow.com/questions/30969597/how-do-i-handle-dyno-restar

Posted 2021-05-09

from django.http import HttpResponse

_current_shutdown_middleware = None

# Used in situations where it must shutdown before it gets initialized
_pre_shutdown = False

class ShutdownMiddleware(object):
    shutting_down = False

    def __init__(self):
        _current_shutdown_middleware = self
        if _pre_shutdown:
            self.shutting_down = True
    
    @staticmethod
    def shutdown_switch():
        """Activate the shutdown switch"""
        self = current_shutdown_middleware
        try:
            self.shutting_down = True
        except AttributeError:
            # Has not processed first request, requesting shutdown
            sys.stderr.write('[ShutdownMiddleware.shutdown_switch] Requested Shutdown, not yet initialized.\n')
            _pre_shutdown = True

    def process_request(self, request):
        if self.shutting_down:
            return HttpResponse('500 internal server error\n'
                         'Server restarting; please try again in 10 seconds.\n', status=500, content_type='text/plain')
        else:
            return None

Hello! I created this gist to demonstrate how you can handle Heroku dyno restarts in Django. This is based off of [this stackoverflow question](http://stackoverflow.com/questions/30969597/how-do-i-handle-dyno-restarts-when-using-django). Many thanks to the writer of the awnser. To put activate the Middleware, you must put this in your django settings file:

```python
MIDDLEWARE_CLASSES = (
    'Middleware.ShutdownMiddleware',
    # All the prexisting classes
    ...
)
```

You should probably put this at the top so you can return the 500 error instantly, but if you have something like [SSLify](https://github.com/rdegges/django-sslify/) you *may* want to put that at the top, but it puts a small barrier between you and the instant server-wide 500 error. That's it!

Thanks to everybody mentioned on the stackoverflow question, including the OP.

Bye! ~CrazyPython

from django.http import HttpResponse
from Middleware import ShutdownMiddleware
import signal
import sys

class TerminationManager(object):

    def __init__(self):
        self._running = True
        signal.signal(signal.SIGTERM, self._start_shutdown)

    def _start_shutdown(self, signum, stack):
        sys.stderr.write('[TerminationManager] Recieved SIGTERM. Stopping new requests.')
        self._running = False
        ShutdownMiddleware.shutdown_switch()
        
termination_manager = TerminationManager()

def dummy_view(request):
    return HttpResponse('Hello! I am a dummy.', content_type='text/plain')