Choosing a Worker Type

The default synchronous workers assume that your application is resource-bound in terms of CPU and network bandwidth. Generally this means that your application shouldn’t do anything that takes an undefined amount of time. An example of something that takes an undefined amount of time is a request to the internet. At some point the external network will fail in such a way that clients will pile up on your servers. So, in this sense, any web application which makes outgoing requests to APIs will benefit from an asynchronous worker.

This resource bound assumption is why we require a buffering proxy in front of a default configuration Gunicorn. If you exposed synchronous workers to the internet, a DOS attack would be trivial by creating a load that trickles data to the servers. For the curious, Hey is an example of this type of load.

Some examples of behavior requiring asynchronous workers:

• Applications making long blocking calls (Ie, external web services)
• Serving requests directly to the internet
• Streaming requests and responses
• Long polling
• Web sockets
• Comet