Struct GitSource 

pub struct GitSource { /* private fields */ }

A file in a git repository, as a configuration source.

Built with GitSource::builder. Not Clone: the working directory is claimed by one source, and two clones fetching into it would interleave their ref updates. Wrap it in an Arc if two places need one.

Implementations

impl GitSource

pub fn builder(url: impl Into<String>) -> Builder

A source reading from the repository at url.

url is anything git understands: https://…, ssh://…, git@host:org/repo.git, or a local path.

pub fn watch<F>( &self, watching: &Watching, interval: Duration, on_change: F, ) -> Result<(), Error>

where F: FnMut(Fetched) -> Result<(), Error>,

Calls on_change when the ref moves, checking every interval.

Polling, because git offers nothing better — and advertisement polling, because transferring a commit every tick to discover it has not changed would be a poor thing to do to a git host. Each tick is one handshake and one ref advertisement; only a ref that moved costs a transfer.

The current value is not delivered at startup, for the same reason a file watcher does not report an edit when it starts. Fetch first if the starting value matters, which it usually does:

sink.apply(source.fetch()?)?;
source.watch(&watching, Duration::from_secs(60), move |document| sink.apply(document))

A host that is away, a ref that has been deleted, a document that does not parse — none of those end the watch. It waits out the interval and tries again. stop is noticed within a quarter second regardless of how long interval is.

A source reading several files can be watched

It is the only one in this family that can. Every other store refuses a watch on a set, and the reason is written down: waking on a change to one key and then re-reading key by key collects the new value of that key and whatever the others happen to be halfway through a deployment — a document that never existed at any instant, installed and then served until the next change.

Neither half of that applies here. What moves is a ref, and what a ref names is a commit — so the watch does not wake on one file, it wakes on the repository, and the re-read that follows takes every file out of that one commit’s tree. A deployment that writes four files in one commit is delivered as one document; a deployment that writes them in four commits is delivered as up to four documents, each of which is a state the repository really was in. There is no interleaving to be had.

The cost is the other direction, and it is the same cost a single-file watch has always had: a commit that touches nothing this source reads still moves the ref, so on_change is called with a document identical to the last one. A spurious delivery, never a torn one — dynamic-config diffs it and reports no changes.

Errors

If the host refuses a credential that cannot be replaced — a token handed in as a constant is the same token next tick, so retrying it forever would be a hot loop against a host that may well start locking the account. A credential that came from a closure is refreshed and retried instead, and only ends the watch if the fresh one is refused too. Or if on_change returns an error, which ends the watch — so a caller that wants to survive a bad document should log it and return Ok.

Trait Implementations

impl Debug for GitSource

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl RemoteSource for GitSource

fn fetch(&self) -> Result<Fetched, Error>

Reads the current document.

fn describe(&self) -> String

How to name this source in an error or a report.