No Server Required
Fossil does not require a central server. Data sharing and synchronization can be entirely peer-to-peer. Fossil uses conflict-free replicated data types to ensure that (in the limit) all participating peers see the same content.
But, a Server Can Be Useful
Fossil does not require a server, but a server can be very useful. Here are a few reasons to set up a Fossil server for your project:
- A server works as a complete project website.
Fossil does more than just version control. It also supports trouble-tickets, wiki, a developer chat room, and a forum. The embedded documentation feature provides a great mechanism for providing project documentation. The unversioned files feature is a convenient way to host builds and downloads on the project website.
- A server gives developers a common point of rendezvous for syncing their work.
It is possible for developers to synchronize peer-to-peer but that requires the developers coordinate the sync, which in turn requires that the developers both want to sync at the same moment. A server alleviates this time dependency by allowing each developer to sync whenever it is convenient. For example, a developer may choose to automatically sync after each commit and before each update. Developers all stay in sync with each other without having to interrupt each other constantly to set up a peer-to-peer sync.
- A server provides project leaders with up-to-date status.
Project coordinators and BDFLs can click on a link or two at the central Fossil server for a project and quickly tell what is going on. They can do this from anywhere — even from their phones — without needing to actually sync to the device they are using.
- A server provides automatic off-site backups.
A Fossil server is an automatic remote backup for all the work going into a project. (Within limits.) You can even set up multiple servers at multiple sites with automatic synchronization between them for added redundancy. Such a setup means that no work is lost due to a single machine failure.
- A server consolidates SQLite corruption risk mitigation to a single point.
The concerns in section 1 of that document assume you have direct access to the central DB files, which isn't the case when the server is remote and secure against tampering.
Section 2 is about file locking, which concerns disappear when Fossil's on the other side of an HTTP boundary and your server is set up properly.
Sections 3.1, 4 thru 6, and 8 apply to all Fossil configurations, but setting up a server lets you address the risks in a single place. Once a given commit is sync'd to the server, you can be reasonably sure any client-side corruption can be fixed with a fresh clone. Ultimately, this is an argument for off-machine backups, which returns us to reason #4 above.
Sections 3.2 and the entirety of section 7 are no concern with Fossil at all, since it's primarily written by the creator and primary maintainer of SQLite, so you can be certain Fossil doesn't actively pursue coding strategies known to risk database corruption.
For another take on this topic, see the article "SQLite Over a Network, Caveats and Considerations". Fossil runs in rollback mode by default per recommendation #3 at the end of that article, and a Fossil server operates as a network proxy for the underlying SQLite repository DB per recommendation #2. This may permit you to safely switch it into WAL mode (fossil rebuild --wal) depending on the underlying storage used by the server itself.
- A server allows Fossil's RBAC system to work.
The role-based access control (RBAC) system in Fossil only works when the remote system is on the other side of an HTTP barrier. (Details.) If you want its benefits, you need a Fossil server setup of some kind.