[MEDIUM] — Stellar event listener persists cursor in cache with global 60s TTL, silently losing the cursor on restart and causing duplicate event processing

[Alqku]

Severity: Medium
Type: Bug
Scope: Stellar
Labels: bug, refactoring, Official Campaign

Description

StellarEventService.saveCursor (src/stellar/stellar-event.service.ts, line ~187) writes stellar:event_listener:cursor = cursor via cacheManager.set. The cache TTL is set globally in RedisModule (src/redis/redis.module.ts, line ~17) to 60000 ms.

If the application restarts more than 60 seconds after the last successful event, get<string>('stellar:event_listener:cursor') returns null and the listener streams from 'now' again. Between the last saved cursor and 'now', a window of unprocessed events is skipped. Restarting more frequently actually routes from the cached cursor, but events newer than 60 s after the last save are silently dropped, and there is no DLQ.

Worse: on restart with a stale cursor in the worst case, all events since the deployment are reprocessed, which can cause duplicate donation confirmations or repeated contract-event job dispatches.

Recommendation

• Persist the cursor in Postgres (a dedicated EventCursor row) instead of Redis with TTL semantics.
• On startup, validate the cursor against the configured network and roll forward if missing.
• Add a small idempotency guard on contract-events queue jobs (e.g. (txHash, eventType) uniqueness key) so duplicate processing is benign.

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[d3vobed]

Hi, I’d like to work on this issue. I will replace the Redis TTL-based cursor storage with persistent Postgres-backed cursor tracking to prevent cursor loss across restarts, add startup validation and recovery logic, and implement basic idempotency protection for event processing to avoid duplicate donation confirmations and contract-event jobs. I have experience working with backend services, event-driven systems, and reliability-focused bug fixes, and I can deliver a clean, well-tested solution.

[GWorld57]

Hello, I'm a fullStack developer with years of experience, I have worked on several projects, can I please work on this.

[grantfox-oss]

🦊 GrantFox — @d3vobed has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #13)
2. Your PR will be reviewed by the OrbitChainLabs maintainers

Good luck! Track your progress on GrantFox.