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Optimizing Kallithea performance

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When serving a large amount of big repositories, Kallithea can start performing

slower than expected. Because of the demanding nature of handling large amounts

of data from version control systems, here are some tips on how to get the best

performance.

Fast storage

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Kallithea is often I/O bound, and hence a fast disk (SSD/SAN) and plenty of RAM

is usually more important than a fast CPU.

Caching

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Tweak beaker cache settings in the ini file. The actual effect of that is

questionable.

Database

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SQLite is a good option when having a small load on the system. But due to

locking issues with SQLite, it is not recommended to use it for larger

deployments.

Switching to MySQL or PostgreSQL will result in an immediate performance

increase. A tool like SQLAlchemyGrate_ can be used for migrating to another

database platform.

Horizontal scaling

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Scaling horizontally means running several Kallithea instances and let them

share the load. That 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