## Save Patching

In order to efficiently get data in and out of running Factorio servers and to provide custom interfaces Clusterio uses save patching<sup>[1]</sup> to add code to the game.
The save patching is based on the built in [event_handler](https://github.com/wube/factorio-data/blob/master/core/lualib/event_handler.lua) library to Factorio and requires scenarios to be coded specifically for it.
Mods on the other hand work without modifications.

This can be disabled with the `factorio.enable_save_patching` config on a per instance basis, however disabling it means that modules are not loaded into the game and most plugins will not function.

<sub>1: Before version 2.0 of Clusterio this was done at runtime with a patcher called Hotpatch, but due to the difficulty in supporting run time patching and the lack of documentation it was replace it with save patching instead.</sub>


## User Accounts

The controller creates and stores accounts for all Factorio users that log into instances under its control.
These accounts are used to store per player data and authorize management of the cluster.
By default users accounts are assigned a Player role that gives a limited read access to the cluster resources, and admins of the cluster can be assigned a Cluster Admin role to get access to manage it.