Trait EngineHandle 

pub trait EngineHandle: Send + Sync {
    // Required methods
    fn resolve_workflow(
        &self,
        workflow_id: &WorkflowId,
    ) -> Result<WorkflowResidency, EngineSeamError>;
    fn deliver_workflow_message(
        &self,
        process: WorkflowProcessHandle,
        message: WorkflowMailboxMessage,
    ) -> Result<(), EngineSeamError>;
    fn spawn_child_workflow(
        &self,
        request: ChildWorkflowSpawnRequest,
    ) -> Result<ChildWorkflowSpawnResult, EngineSeamError>;
    fn terminate_linked_child_workflow(
        &self,
        parent_workflow_id: &WorkflowId,
        child_process: WorkflowProcessHandle,
        correlation: u64,
    ) -> Result<(), EngineSeamError>;
    fn terminate_linked_activity(
        &self,
        parent_workflow_id: &WorkflowId,
        activity_process: Pid,
        correlation: u64,
    ) -> Result<(), EngineSeamError>;
    fn arm_timer(&self, entry: TimerWheelEntry) -> Result<(), EngineSeamError>;
    fn disarm_timer(
        &self,
        process: WorkflowProcessHandle,
        timer_id: &TimerId,
    ) -> Result<(), EngineSeamError>;
    fn record_workflow_event(
        &self,
        workflow_id: &WorkflowId,
        event: Event,
    ) -> Result<RecordOutcome, EngineSeamError>;
    fn record_redelivered_timer_fire(
        &self,
        workflow_id: &WorkflowId,
        timer_id: &TimerId,
    ) -> Result<RedeliveredFire, EngineSeamError>;
}

Engine-facing capabilities consumed by AT services and implemented by AE.

This trait deliberately does not expose operations that start, supervise, tear down, or load top-level workflow processes. Child spawning, residency resolution, and recording are requests into AE/AD-owned infrastructure. In particular, EngineHandle::record_workflow_event must route asynchronous-arrival events through the target workflow’s single Recorder; AT services must not append directly to the event store.

Required Methods

fn resolve_workflow( &self, workflow_id: &WorkflowId, ) -> Result<WorkflowResidency, EngineSeamError>

Resolves a workflow identifier to its current residency state.

Errors

Returns EngineSeamError when AE cannot inspect residency for the requested workflow.

fn deliver_workflow_message( &self, process: WorkflowProcessHandle, message: WorkflowMailboxMessage, ) -> Result<(), EngineSeamError>

Delivers a message to a resident workflow process mailbox.

Errors

Returns EngineSeamError when AE cannot enqueue the message on the target mailbox.

fn spawn_child_workflow( &self, request: ChildWorkflowSpawnRequest, ) -> Result<ChildWorkflowSpawnResult, EngineSeamError>

Requests AE to spawn a child workflow execution linked to the parent process.

Errors

Returns EngineSeamError when AE rejects or fails the linked child-spawn request.

fn terminate_linked_child_workflow( &self, parent_workflow_id: &WorkflowId, child_process: WorkflowProcessHandle, correlation: u64, ) -> Result<(), EngineSeamError>

Terminates a linked child workflow process through AE’s process-link boundary.

Errors

Returns EngineSeamError when AE cannot send the cancellation exit to the linked child.

fn terminate_linked_activity( &self, parent_workflow_id: &WorkflowId, activity_process: Pid, correlation: u64, ) -> Result<(), EngineSeamError>

Terminates a linked in-VM activity process through AE’s process-link boundary.

Errors

Returns EngineSeamError when AE cannot send the cancellation exit to the linked child.

fn arm_timer(&self, entry: TimerWheelEntry) -> Result<(), EngineSeamError>

Arms a timer-wheel entry for a resident workflow process.

Errors

Returns EngineSeamError when AE cannot register the timer with the live wheel.

fn disarm_timer( &self, process: WorkflowProcessHandle, timer_id: &TimerId, ) -> Result<(), EngineSeamError>

Disarms a timer-wheel entry for a resident workflow process.

Errors

Returns EngineSeamError when AE cannot remove the timer from the live wheel.

fn record_workflow_event( &self, workflow_id: &WorkflowId, event: Event, ) -> Result<RecordOutcome, EngineSeamError>

Records an event through the target workflow’s single AD Recorder.

Returns RecordOutcome::Recorded when the event was durably appended, RecordOutcome::AlreadyRecorded when an earlier acknowledgement-lost append of the same timer fire is found already durable (nothing is appended and the recorder’s tracked head is reconciled forward — aion#145), or RecordOutcome::RefusedTerminal when the append was declined because the active run already recorded a terminal (a benign late arrival). Callers that follow a recorded fire with a mailbox wake MUST deliver it for Recorded AND AlreadyRecorded — the durable record exists in both — and MUST withhold it for RefusedTerminal, which must not reschedule a terminated workflow.

Errors

Returns EngineSeamError when the target workflow’s Recorder cannot append the event.

fn record_redelivered_timer_fire( &self, workflow_id: &WorkflowId, timer_id: &TimerId, ) -> Result<RedeliveredFire, EngineSeamError>

Answers, under the recorder lock, whether a REDELIVERY of an already-recorded fire for timer_id still owes its mailbox wake.

This is the redelivery twin of Self::record_workflow_event and the only seam a redelivery may use: it NEVER appends. When the timer’s disposition is still the recorded fire, the recorder’s tracked head is reconciled forward to the durable head (aion#145) and RedeliveredFire::WakeOwed instructs the caller to deliver the wake. Any other disposition — the timer re-armed or cancelled since the caller’s observation — answers RedeliveredFire::NotOwed without touching history; routing a redelivery through the generic append path instead would record a premature TimerFired for the NEW arming. A terminal active run answers RedeliveredFire::RefusedTerminal.

Errors

Returns EngineSeamError when the target workflow’s recorder cannot be reached.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors

impl EngineHandle for Engine