This class and its members can be considered a stable interface and will not change in a backwards-incompatible fashion between releases of Unicorn. Knowledge of this class is generally not not needed for most users of Unicorn.
Some users may want to access it in the before_fork/after_fork hooks. See the Unicorn::Configurator RDoc for examples.
In most cases, you should be using the Unicorn::Configurator#user directive instead. This method should only be used if you need fine-grained control of exactly when you want to change permissions in your after_fork hooks.
Changes the worker process to the specified user and group This is only intended to be called from within the worker process from the after_fork hook. This should be called in the after_fork hook after any privileged functions need to be run (e.g. to set per-worker CPU affinity, niceness, etc)
Any and all errors raised within this method will be propagated directly back to the caller (usually the after_fork hook. These errors commonly include ArgumentError for specifying an invalid user/group and Errno::EPERM for insufficient privileges