antigravity-skills-reference/web-app/public/skills/dbos-python/references/pattern-idempotency.md

title, impact, impactDescription, tags

title	impact	impactDescription	tags
Use Workflow IDs for Idempotency	MEDIUM	Prevents duplicate executions of critical operations	idempotency, workflow-id, deduplication, exactly-once

Use Workflow IDs for Idempotency

Set workflow IDs to make operations idempotent. A workflow with the same ID executes only once.

Incorrect (duplicate payments possible):

@app.post("/pay/{order_id}")
def process_payment(order_id: str):
    # Multiple clicks = multiple payments!
    handle = DBOS.start_workflow(payment_workflow, order_id)
    return handle.get_result()

Correct (idempotent with workflow ID):

from dbos import SetWorkflowID

@app.post("/pay/{order_id}")
def process_payment(order_id: str):
    # Same order_id = same workflow ID = only one execution
    with SetWorkflowID(f"payment-{order_id}"):
        handle = DBOS.start_workflow(payment_workflow, order_id)
    return handle.get_result()

@DBOS.workflow()
def payment_workflow(order_id: str):
    charge_customer(order_id)
    send_confirmation(order_id)
    return "success"

Access the workflow ID inside workflows:

@DBOS.workflow()
def my_workflow():
    current_id = DBOS.workflow_id
    DBOS.logger.info(f"Running workflow {current_id}")

Workflow IDs must be globally unique. Duplicate IDs return the existing workflow's result without re-executing.

Reference: Workflow IDs and Idempotency