# Run Gunicorn with Gevent

## Gunicorn + Gevent

If you already have a wsgi application written in Flask/Django/Webpy, and you want to run it with gunicorn, suppose your `application` variable is in `wsgi.py` file:

```bash
$ pip install gunicorn
$ gunicorn -w 2 wsgi:application
```

By default guicorn is running in `sync` mode, if your application is I/O bound, use `gevent` mode may increase its performance:

```
$ pip install gunicorn
$ pip install gevent
$ gunicorn -w 2 -k gevent wsgi:application
```

You don't even need to change your code. If you searched this, some other articles may mention you need to add code to do a "monkey patch", e.g. if your gunicorn's configure file is `gunicorn_conf.py`, then add this to that file:

```python
from gevent import monkey
monkey.patch_all()
```

**BUT you really don't need to add this**, because gunicorn will auto path this, here is the code snippet from gunicorn:

```python
from gevent import hub, monkey, socket, pywsgi

class GeventWorker(AsyncWorker):
    ...
    def patch(self):
        monkey.patch_all()
        ...
    ...
    
    def init_process(self):
        self.patch()
        hub.reinit()
        super().init_process()
```

So you can see in the `init_process` function, guinicorn will call the `patch` function, which will call the `monkey.patch_all()` function.

In short, to run gunicorn with gevent, you only need to install the gevent package and change the worker_class to be "gevent".

## Reference:
* [Gunicorn](https://gunicorn.org)
* [Gunicorn ggevent.py](https://github.com/benoitc/gunicorn/blob/master/gunicorn/workers/ggevent.py#L144)