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Rainbow Saddle

Note

I no longer use rainbow-saddle, and thus cannot actively maintain it.

rainbow-saddle is a wrapper around Gunicorn to simplify code reloading without dropping requests.

Installation

Install from pypi:

$ sudo pip install rainbow-saddle

Or from source:

$ sudo ./setup.py install

Why?

Sometimes doing a kill -HUP <gunicorn PID> is not sufficient to reload your code. For example it doesn't work well if you host your code behind a symlink, or if a .pth in your installation is updated to point to a different directory.

The correct way to reload code in such situations is a bit complicated:

# Reexec a new master with new workers
/bin/kill -s USR2 `cat "$PID"`
# Graceful stop old workers
/bin/kill -s WINCH `cat "$PIDOLD"`
# Graceful stop old master
/bin/kill -s QUIT `cat "$PIDOLD"`

It also has the downside of changing the "master" process PID, which confuses tools such as supervisord.

rainbow-saddle handles all of this for you, and never changes its PID. Reloading code becomes as simple as sending a SIGHUP again:

$ rainbow-saddle --pid /tmp/mysite.pid gunicorn_paster development.ini --log-level debug
$ kill -HUP `cat /tmp/mysite.pid`