Struct EngineCfg 

pub struct EngineCfg {
    pub try_only: bool,
    pub max_retry: u32,
    pub backoff_ms_step: u64,
    pub max_hold_ms: u128,
    pub token_secret: Vec<u8>,
    pub long_hold: LongHoldConfig,
    pub max_spawn_depth: u32,
}

Lock acquisition + max-hold guard configuration.

Fields

try_only: bool

When true, Engine::with_state never retries on a busy lock — it fails fast with EngineError::LockBusy on the very first try_lock miss instead of backing off and retrying.

max_retry: u32

Max number of try_lock retries before giving up with EngineError::LockBusyAfterRetry (ignored when try_only = true).

backoff_ms_step: u64

Linear backoff step (ms) between retries; the sleep duration for attempt n is backoff_ms_step * (n + 1).

max_hold_ms: u128

R4 guard threshold: if a single with_state closure holds the lock longer than this (ms), with_state panics — a signal that a long operation leaked inside the lock in violation of the R3 discipline.

token_secret: Vec<u8>

HMAC secret used by TokenSigner to sign/verify CapTokens.

Default generates this fresh (32 random bytes from the OS RNG) on every call when the caller does not supply one — set it explicitly for tokens to stay valid across restarts, or when multiple independently-constructed engines/signers must accept each other’s tokens.

long_hold: LongHoldConfig

Long-hold session tuning (idle keepalive, heartbeat cadence).

max_spawn_depth: u32

Worker recursive spawn depth ceiling (guards against unbounded spawn).

When Ctx.meta.runtime["spawn_depth"] has already reached this value and a Worker token tries to call start_task, the engine raises EngineError::SpawnDepthExceeded. 0 = root (a task launched directly by an Operator); 4 = default, which allows four levels of nested sub-tasks.

Implementations

impl EngineCfg

pub fn strict() -> Self

Strict variant: try_only = true (no retry/backoff) and a tight max_hold_ms = 10. Useful for tests that want lock contention to fail fast rather than silently wait.

pub fn relaxed() -> Self

Relaxed variant: higher max_retry / backoff_ms_step / max_hold_ms than the default, for environments where lock contention is expected to be more frequent or operations slower.

Trait Implementations

impl Clone for EngineCfg

fn clone(&self) -> EngineCfg

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for EngineCfg

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

Formats the value using the given formatter.

impl Default for EngineCfg

fn default() -> Self

Baseline configuration: bounded retry with backoff, a generous (but non-zero) max_hold_ms, and max_spawn_depth = 4. token_secret is generated fresh per call — see the field doc.