Struct StoreOpenGuard 

pub struct StoreOpenGuard { /* private fields */ }

The single-writer store lock: an exclusive advisory lock on <store>/.coven-lock, held for the life of a full open handle (and its running sync loop). A second full open of the same store is refused with StoreOpenGuardError::AlreadyOpen while the lock is held — the invariant that keeps two writers from racing the same db and blob store.

Read-only opens take no lock

A read-only open deliberately does not touch this lock. The lock is exclusive, so a shared lock on the same file would block against a writer that already holds it (and vice versa) — a reader could never coexist with the writer it exists to read alongside. But a read-only open needs no lock at all: the lock guards against a second writer, and a read-only handle holds a SQLITE_OPEN_READONLY connection that cannot write. So a read-only open skips the guard entirely. Cross-process safety comes from WAL mode (a reader sees committed rows while the writer commits more), not from this lock; the blob cache a reader may populate is per-device scratch written atomically (temp + rename), so a reader and the writer touching the same cache file never tear it. This lets one writer and any number of read-only readers coexist on one store.

Implementations

impl StoreOpenGuard

pub fn acquire(store_dir: &StoreDir) -> Result<Self, StoreOpenGuardError>

pub fn acquire_for_test(store_dir: &StoreDir) -> Arc<Self>

Acquire the guard for a test, panicking on refusal.