# Python web servers

The Python agent is tested against several common production web servers. Some servers require certain configuration options in order to work properly with Contrast.

## uWSGI configuration

Contrast requires the following configuration options when running on uWSGI. You can set these on the command line or in your uWSGI configuration (.ini) file:

• --enable-threads: Contrast's machinery utilizes threads. This option must be enabled so the agent can start background threads.

• --single-interpreter: The Python agent applies its instrumentation to the Python process in which it is initialized. This option ensures that Contrast is initialized in the same process that handles requests for your application.

• If using --master you must also use --lazy-apps: When running in master mode, uWSGI initializes the application in a master process but forks this process into workers which handle requests. To operate correctly, Contrast must be initialized independently in each worker process; --lazy-apps achieves this.