.. _env_vars: Environment Variables ====================== Eventlet's behavior can be controlled by a few environment variables. These are only for the advanced user. EVENTLET_HUB Used to force Eventlet to use the specified hub instead of the optimal one. See :ref:`understanding_hubs` for the list of acceptable hubs and what they mean (note that picking a hub not on the list will silently fail). Equivalent to calling :meth:`eventlet.hubs.use_hub` at the beginning of the program. EVENTLET_THREADPOOL_SIZE The size of the threadpool in :mod:`~eventlet.tpool`. This is an environment variable because tpool constructs its pool on first use, so any control of the pool size needs to happen before then. EVENTLET_TPOOL_DNS If set to 'yes', uses :func:`eventlet.tpool.execute` to call :func:`~socket.gethostbyname` and :func:`~socket.getaddrinfo`, making them appear non-blocking. This environment variable is ignored on OS X.