Struct StatCache 

pub struct StatCache<T> { /* private fields */ }

A parse cache keyed by a file’s (mtime, len): the file is re-read and re-parsed only when its stat changes.

For pollers reading run state on a tick. The dashboard synced at 10Hz by re-parsing every run’s meta.json, stages.json, and whole context.json; with 50 runs on disk that was on the order of 100 MB/s of allocate-and-parse-and-free for files that change at most once per persist tick. A stat costs microseconds; this turns the steady-state tick into stats plus clones of shared Arcs.

(mtime, len) rather than mtime alone: the persistence lane’s atomic rename gives every update a fresh temp inode and mtime, but coarse mtime granularity on some filesystems can miss two updates in the same instant - the length check catches most of those, and a same-length same-instant rewrite is indistinguishable anyway one tick later.

Implementations

impl<T> StatCache<T>

pub fn get_with( &mut self, path: &Path, parse: impl FnOnce(&str) -> Option<T>, ) -> Option<Arc<T>>

The value parsed from path, re-reading only when the file’s stat changed since the last call. None when the file is missing, unreadable, or parse rejects it - negative results are cached too, so a persistently-bad file costs one stat per tick, not one parse.

pub fn retain_under(&mut self, keep: &HashSet<PathBuf>)

Drop entries for files under runs that no longer exist, so a long-lived poller’s cache stays bounded by the live run set.

Trait Implementations

impl<T> Default for StatCache<T>

fn default() -> Self

Returns the “default value” for a type.