Struct SagaCoordinator 

pub struct SagaCoordinator {
    next_saga_id: AtomicU64,
    in_flight: Mutex<HashMap<u64, InFlightSaga>>,
    events_tx: Sender<Event>,
    state: Arc<Mutex<State>>,
    log: Option<Arc<LauncherSagaLog>>,
    host_pipe: Option<Arc<HostPipe>>,
}

Fields

next_saga_id: AtomicU64

Monotonic saga-id allocator.

in_flight: Mutex<HashMap<u64, InFlightSaga>>

In-flight sagas keyed by saga_id, each wrapped with the durable-log bookkeeping (LSD-2: awaiting_step + next_step_index).

events_tx: Sender<Event>

Reference to the broadcast bus so the coordinator can emit SagaStarted / SagaCompleted / SagaFailed.

state: Arc<Mutex<State>>

Reference to the launcher’s reducer state for bump_version when emitting saga lifecycle events.

log: Option<Arc<LauncherSagaLog>>

LSD-2 — durable saga log. None in tests that don’t exercise the durability path (the saga then logs + remains in flight, preserving the pre-LSD-2 behavior tests rely on for end-to-end bracket assertions). When Some, every saga lifecycle transition (spawn_saga → start_saga, IssueCmd → start_step, awaited-event consumed → finish_step, Done → terminate_saga(Completed), Failed / evicted → terminate_saga(Failed)) writes to this log.

host_pipe: Option<Arc<HostPipe>>

CPD-3 — launcher → host pipe wrapper. apply_action for IssueCmd::Host dispatches via host_pipe.send_command() when installed. None in tests that don’t exercise host dispatch (those drive sagas via synthetic terminal events on the bus).

Implementations

impl SagaCoordinator

pub fn new(events_tx: Sender<Event>, state: Arc<Mutex<State>>) -> Self

pub fn with_host_pipe(self, host_pipe: Arc<HostPipe>) -> Self

CPD-3 — install the host pipe so IssueCmd::Host actions are dispatched live (instead of log-only). Builder-style setter so existing tests + the next_id_is_monotonic smoke don’t have to construct a HostPipe. Production wiring (main.rs) calls this once before run_coordinator is spawned.

pub fn with_log(self, log: Arc<LauncherSagaLog>) -> Result<Self, LogError>

LSD-2 — install the durable saga log so saga lifecycle transitions are persisted to <data-dir>/db/launcher-sagas.db. Builder-style setter rather than a constructor parameter so existing tests + the next_id_is_monotonic smoke don’t have to construct an in-memory log. Production wiring (in main.rs) calls this once before run_coordinator is spawned.

pub fn next_id(&self) -> u64

Allocate the next saga_id. Monotonic per launcher run.

async fn next_event_version(&self) -> u64

Bump the launcher’s event_version for a coordinator-emitted lifecycle event. Brief mutex hold — no I/O between lock and drop.

async fn emit_started(&self, saga_id: u64, name: &'static str)

Emit Event::SagaStarted after registering a saga.

async fn emit_completed(&self, saga_id: u64)

Emit Event::SagaCompleted after a saga returns Done.

async fn emit_failed(&self, saga_id: u64, reason: String)

Emit Event::SagaFailed after a saga returns Failed or after evict-and-replace cancels a same-kind in-flight saga. F.7 cleanup audit: prior #[allow(dead_code)] removed — F.6 evict-and-replace policy now actively dispatches this on every concurrent same-kind retrigger.

async fn apply_action( &self, saga_id: u64, name: &'static str, action: SagaAction, step_index: u32, ) -> ApplyOutcome

Apply a SagaAction returned by start or on_event. Returns an ApplyOutcome carrying:

• in_flight: true → caller keeps the saga in in_flight, false → caller removes it.
• awaiting_step: Some(idx) if the action was an IssueCmd that allocated step idx and the saga is now parked waiting for the echo event. Caller stores this on the InFlightSaga so the next non-Wait on_event return can call LauncherSagaLog::finish_step(saga_id, idx, ev).

CPD-3 — IssueCmd::Host dispatches live through HostPipe when one is installed. Tests without a host_pipe (the existing F.5/F.6 unit + integration tests) fall back to log-only so synthetic-terminal-event drivers continue to work. LauncherSelf and Srv targets remain log-only — reserved for class-D/E sagas, no consumer today.

LSD-2 — every state transition writes to LauncherSagaLog when one is installed: IssueCmd → start_step, Done → terminate_saga(Completed), Failed → terminate_saga(Failed).

step_index is the caller-allocated index for THIS dispatch. On the first dispatch in spawn_saga, the caller passes 0; on subsequent dispatches from the event loop, the caller pulls

• bumps the per-InFlightSaga counter.

Terminal paths (Done, Failed, host-send-error) all go through claim_terminal so only one of {normal Done/Failed, timeout-task, SagaActionFailed listener, host-send-error} can win the terminal-event race for a given saga_id. (reagent P1 PR #644 round 1 + 2.)

async fn claim_terminal(&self, saga_id: u64) -> bool

Atomically remove saga_id from in_flight and return whether the caller was the one who removed it (i.e. has the right to emit the terminal SagaCompleted / SagaFailed). Idempotent: a second caller for the same saga_id sees false. Used by the SagaAction::Done and SagaAction::Failed paths in apply_action, by the per-saga timeout task in spawn_saga, by the Event::SagaActionFailed listener in run_coordinator, by the host-send-failure path in apply_action::IssueCmd::Host, and by the eviction path in run_coordinator. (reagent P1 PR #644 round 1.)

async fn spawn_saga(self: &Arc<Self>, saga: Box<dyn Saga>) -> u64

Register a fresh saga, calling start and applying its first action. The caller has already determined that the saga should fire (e.g. matched a trigger event). Returns the saga’s allocated id (logged + bracketed in SagaStarted).

LSD-2 — also writes a running row to the durable saga log before invoking saga.start(), and (via apply_action) records the saga’s first dispatched step.

CPD-3 — also arms a per-saga deadline timer. If the saga is still in_flight when saga.timeout() elapses, a background task force-fails it (SagaFailed { reason: "saga timeout" }) and removes it from the registry. Per spec §3.10. Insert-then- start ordering is required so apply_action’s claim_terminal guard can succeed for immediate-completion sagas (codex P2 PR #644 round 2).