A single-user database for Mac and iOS that provides multi-client synchronization using cloud storage
SlouchDB4 is a CRDT-style distributed journal-based database for single-user/multi-device scenarios. It is written in Swift and
so is currently only available for macOS and iOS clients.
SlouchDB4 lets you write an app that saves diff changes to its own local journal. It can interop with a shared file storage
(such as Dropbox, OneDrive, iCloud) and upload its own journal files as well as download journal files generated by other
clients. It will then merge the remote changes into its local journal history to update the state of the database.
This database is meant for single-user only because it uses a very primitive conflict-resolution system: the last update wins.
Additionally, the clock it uses to order edits across multiple platforms is not synchronized. It is assumed that each peer
uses a clock that’s “pretty close” to the other peers. In other words, we are relying on a single user to be slow enough in
making edits across multiple devices that clock synchronization is not an issue.
This is a rewrite of SlouchDB. It is the 4th version. SlouchDB2 was another attempt and was being updated as well as used in my own personal apps. However, I soon noticed it would not scale to
large databases since all data was loaded into memory. I wanted it to support massive databases and ensure everything could be
stored to disk and cached in-mem only as necessary. SlouchDB3 (never released) was started to handle this at the beginning of
January 2020. After a couple of weeks of implementation, I realized the architecture could be even more improved, so rewrote it
again before it got too far. Hence, SlouchDB4.
This is a work in progress. See TODOs.md for regular updates (adding of new tasks as well as marking old tasks done). It’s in
a pre-alpha stage, but progress is being made quickly. Short term goals: