---
id: fccd4277-a253-4f7f-8065-7a9cffd64354
type: fix
title: "Fix: Prevent duplicate POSTs when audit update fails after successful delivery in outbound-event-handler"
tags: [esb-monorepo, tac, outbound-event-handler, error-handling, fix, cloud-functions, idempotency, duplicate-prevention]
importance: 0.7
confidence: 0.8
created: "2026-02-25T17:47:36.634745+00:00"
updated: "2026-02-26T18:58:20.763237+00:00"
relations:
  - target: ca8d0390-7ff9-4ca7-b033-3656d653c2be
    type: FOLLOWS
    direction: outgoing
    strength: 0.7
    edge_id: e5812091-5454-4f1b-ae62-23f2bec97f33
---

# Fix: Duplicate POST Prevention on Audit Failure

## Project
esb-monorepo — TAC `outbound-event-handler` (GCF)

## Problem
Bitbucket Rovo Dev flagged a code design issue: if `update_processed_events()` fails at Step 5 (after all POSTs to `outbound-object-router` succeeded), the function returned HTTP 500. Cloud Scheduler treats any 5xx as a failure and retries, causing duplicate POSTs to the downstream router for events that were already delivered.

## Root Cause
The final audit DB update call (`update_processed_events`) was not wrapped in error handling. A transient DB failure at that step caused the function to surface a 500, even though all delivery work was complete.

## Fix
Wrapped the final `update_processed_events` call in a `try/except` block:
- Logs the audit error at ERROR level
- Still returns **200** because all deliveries succeeded — the audit failure is non-fatal
- Cloud Scheduler will NOT retry, preventing duplicate POSTs

## Important Distinction
The partial-progress flush in the POST failure path (~line 165) is intentionally **NOT** wrapped. In that case we DO want 500 returned so Cloud Scheduler retries the failed POST delivery.

```python
# Step 5 — audit update: non-fatal, deliveries already complete
try:
    update_processed_events(processed_ids)
except Exception as e:
    logger.error("Audit update failed after successful delivery: %s", e)

return make_response("OK", 200)
```

## Test Added
`test_audit_update_failure_after_all_posts_succeed_returns_200`

## Commit
`320b871` on `dev-object-handler` branch