UPGRADING.md

== Upgrading From Switchman 2.0/Rails 6.0 or older ==

With Rails 6.1, Rails has sufficient support for both horizontal and vertical sharding to implement Switchman's connection management on top of, instead of significantly replacing a good chunk of Rail's internal code. This has resulted in some major changes:

• GuardRail no longer supports a global configuration and modifying it. Instead you should use an ERB for your database.yml so that whatever you were going to apply is already done there.
• Shard categories are no more. Instead, you should use a parent class, and call sharded_model on it to fulfill the same purpose. To get the shard category of a class, call its connection_class_for_self method. This also means any activate methods that took symbols now takes the actual class.
• Separate connection trees can no longer share connections. In particular this means that for unsharded models, they will not share a connection with the default shard for regular models. In practice, if you're having problems with too many connections to the default shard now, you're accessing the default shard too much and likely need to improve your caching in order to avoid this.
• In specs, @shard3 is no longer available. @shard1 is now guaranteed to share a connection with the default shard.