Elamur Groupantsmova-seaspider-singleton
The groupant beside tools/seaspider/src/singleton.rs in the Mova repository: what the code computes, what it never does, how to go back from its outputs, its invariants, cost and checks.
Facts
Implementation material. A Mova code model describes this code at one source revision: partial models, finite checks and their stated scope. It is not a reviewed general exposition, and its labels are shown as written, never raised.
Components
| component | label | where |
|---|---|---|
| approximant | partial | Forward approximant |
| ast | partial | syntax.json |
| composition | partial | Composition |
| cost | partial | Cost |
| descriptant | present | Descriptant |
| invariant | partial | Invariant |
| tests | finite evidence | tests |
Obernants
The typed relations around the forward model: the behaviour complement (what the code never does), the reverse reconstruction (every input compatible with an output) and specialised views.
| id | type | label | where |
|---|---|---|---|
behavior_complement | behavior_complement | partial source derived model | behavior_complement |
reverse_reconstruction | reverse_reconstruction | partial source derived model | reverse_reconstruction |
Model text
model
mova-seaspider-singleton
Descriptant
One Sea Spider per host: an exclusive flock on the configured lock file held for the life of serve, fetch or robots; the holder records pid, role and start; a second start reports the holder. Source: tools/seaspider/src/singleton.rs.
Forward approximant
acquire(path, role): create parent dirs, open, try_lock; WouldBlock -> Refused::Running{holder from the file}; else truncate and write {pid, role, started_unix}, fsync, return Singleton.
Invariant
Lock file with one JSON line {pid, role, started_unix}; the lease is the open file description.
Cost
One open, one flock attempt, one small write and fsync.
Composition
Parent: seaspider.
behavior_complement
no waiting for the lease, no stealing a lease, no cross-host or cross-lock-path exclusion; the kernel releases the lease at exit (no stale lease). Evidence status: source-derived model with finite checks, not a proof.
reverse_reconstruction
the lock file recovers the last holder pid, role and start; earlier holders are not recoverable. No unique inverse is claimed.
tests
Checks
cargo test --manifest-path tools/seaspider/Cargo.toml --offline --locked with MOVA_OCTOPUS_TEST_MODEL=$MOVA_DATA/download/0/0.4/en.bin (34 unit + 9 end-to-end + 1 singleton CLI + 2 English tests; two identical runs on 2026-11-04) Negative controls 2026-11-04: a lock that always succeeds turns the singleton unit and CLI tests red; admitting every caller turns the served English test red (the Whale's fetch is queued); restored afterwards. These are finite fixtures; not a proof.
This page in Markdown → https://md.groupants.elamur.ai/free/en/mova/tools/seaspider/src/singleton.rs.groupant/