==================
WSGISwitchInterval
==================

:Description: Override the Python GIL switch interval (``sys.setswitchinterval``).
:Syntax: ``WSGISwitchInterval`` *seconds*
:Default: *Python's built-in default* (``0.005`` = 5 ms in CPython 3.2+)
:Context: server config

Sets the Python interpreter's GIL switch interval at process start by
calling ``sys.setswitchinterval()`` once after the interpreter has been
initialised. The argument is the same form ``sys.setswitchinterval()``
accepts — a positive number of seconds expressed as a float. The
interval controls how often the thread holding the GIL checks whether
to release it for another waiting thread.

For example, to set the interval to 2 ms::

  WSGISwitchInterval 0.002

When the directive applies the value, mod_wsgi emits an INFO entry to
the Apache error log naming the value that was set.

This directive only affects the embedded interpreter created in Apache
child processes when embedded mode is used. To set the switch interval
for interpreters running in daemon processes, use the
:ref:`switch-interval <switch-interval>` option to the
:doc:`WSGIDaemonProcess` directive instead. Different daemon groups
can run with different intervals by setting the option differently on
each ``WSGIDaemonProcess`` directive.

For most modern deployments, daemon mode is the preferred deployment
method, in which case configure the switch interval via
``WSGIDaemonProcess`` rather than this directive.

The directive is also valid inside a :doc:`WSGIInterpreterOptions`
container. When nested, the value applies only to interpreters
matched by the container's selectors, and may differ between
interpreters in the same process when those interpreters have been
given their own GIL via :doc:`WSGIPerInterpreterGIL`. Under the
shared GIL the switch interval is a process-global value and
``application-group=`` scoping of this directive is rejected; see
:doc:`WSGIInterpreterOptions` for the full rules.

This directive has no effect in a process where free-threading is
active via :doc:`WSGIFreeThreading`. The switch interval governs how
often the GIL is yielded; with no GIL there is nothing to yield.
mod_wsgi logs a warning and skips the ``sys.setswitchinterval()``
call.