migrating to another database platform.

4. Scale Kallithea horizontally

    Scaling horizontally can give huge performance benefits when dealing with

    large amounts of traffic (many users, CI servers, etc.). Kallithea can be

    scaled horizontally on one (recommended) or multiple machines.

    It is generally possible to run WSGI applications multithreaded, so that

    several HTTP requests are served from the same Python process at once. That

    can in principle give better utilization of internal caches and less

    process overhead.

    One danger of running multithreaded is that program execution becomes much

    more complex; programs must be written to consider all combinations of

    events and problems might depend on timing and be impossible to reproduce.

    Kallithea can't promise to be thread-safe, just like the embedded Mercurial

    backend doesn't make any strong promises when used as Kallithea uses it.

    Instead, we recommend scaling by using multiple server processes.

    Web servers with multiple worker processes (such as ``mod_wsgi`` with the

    ``WSGIDaemonProcess`` ``processes`` parameter) will work out of the box.

    In order to scale horizontally on multiple machines, you need to do the