Trigger Actions

Comparable to: RPC vs message queue vs fire-and-forget patterns

Key Concepts

Use the concepts below when they fit the task. Not every invocation needs all three modes.

• Synchronous (default): caller blocks until the function returns a result or times out
• Void (TriggerAction.Void()): fire-and-forget dispatch, returns immediately, no retry guarantees
• Enqueue (TriggerAction.Enqueue({ queue })): routes through a named queue with automatic retries and backoff, returns a messageReceiptId
• Decision guide: need the result? use sync. Must complete reliably? use enqueue. Optional side effect? use void.

Architecture

The caller invokes trigger() with an optional action parameter. Synchronous mode waits for the handler result. Void mode dispatches and returns immediately. Enqueue mode places the payload on a named queue where a consumer processes it with retry guarantees.

iii Primitives Used

Reference Implementation

See ../references/trigger-actions.js for the full working example — a comparison of all three

Also available in Python: ../references/trigger-actions.py

Also available in Rust: ../references/trigger-actions.rs invocation modes showing when and how to use sync, void, and enqueue patterns.

Common Patterns

Code using this pattern commonly includes, when relevant:

• await iii.trigger({ function_id: 'users::get', payload: { id } }) — sync, get result directly
• iii.trigger({ function_id: 'analytics::track', payload: event, action: TriggerAction.Void() }) — fire-and-forget
• iii.trigger({ function_id: 'orders::process', payload: order, action: TriggerAction.Enqueue({ queue: 'payments' }) }) — durable enqueue
• Sync returns the function result directly
• Void returns undefined in Node/browser, None in Python, and Value::Null in Rust
• Enqueue returns { messageReceiptId: string } as JSON; Rust may deserialize to EnqueueResult { message_receipt_id }
• iii trigger --function-id='users::get' --payload='{"id":"123"}' — invoke via CLI
• iii trigger --function-id='users::get' --payload='{"id":"123"}' --timeout-ms=5000 — with custom timeout

Timeout and Error Behavior

• The default invocation timeout is 30 seconds unless overridden by SDK init options or per-call timeoutMs / timeout_ms.
• Sync invocation surfaces handler errors, engine errors, RBAC denial, and timeout errors to the caller.
• Void invocation only confirms dispatch; it does not return handler results and does not give retry guarantees.
• Enqueue confirms message acceptance. Handler failures are retried according to queue configuration and may later land in a dead letter queue.
• Use iii-error-handling for FORBIDDEN, TIMEOUT, function_not_found, function_not_invokable, invocation_failed, and invocation_stopped.

Adapting This Pattern

Use the adaptations below when they apply to the task.

• Default to synchronous when the caller needs the result to proceed
• Use void for logging, analytics, or any side effect where failure is acceptable
• Use enqueue for anything that must complete reliably — payments, emails, notifications
• Combine modes in a single handler: sync call for validation, then enqueue for processing
• Named queues let you configure retries and concurrency per workload type

Pattern Boundaries

• For queue configuration (retries, concurrency, FIFO ordering), prefer iii-engine-config.
• For DLQ handling when enqueued jobs exhaust retries, prefer iii-dead-letter-queues.
• For error handling, prefer iii-error-handling.
• For function registration and trigger binding, prefer iii-functions-and-triggers.
• Stay with iii-trigger-actions when the primary problem is choosing the right invocation mode.

When to Use

• Use this skill when the task is primarily about iii-trigger-actions in the iii engine.
• Use this skill even when the request does not say "enqueue" if work is slow, retryable, reliable, or should continue after the caller returns.

Boundaries

• Never use this skill as a generic fallback for unrelated tasks.
• You must not apply this skill when a more specific iii skill is a better fit.
• Always verify environment and safety constraints before applying examples from this skill.