Newbranchnotify6#76
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June 19, 2026 09:15
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Implemented a reliable scheduled notification infrastructure that enables notifications to be queued and delivered at a specified future date and time rather than being sent immediately.
Overview
This implementation introduces persistent storage, background job processing, fault tolerance, and recovery mechanisms to ensure notifications are delivered accurately and reliably, even across application restarts or temporary outages.
Features Implemented
Scheduled Notification Persistence
Added database support for storing scheduled notifications.
Tracked notification payloads, recipients, execution timestamps, processing status, retry counts, and audit metadata.
Introduced lifecycle states including PENDING, PROCESSING, COMPLETED, and FAILED.
Background Processing System
Implemented a dedicated scheduler/worker responsible for continuously monitoring pending notifications.
Automatically discovers notifications whose scheduled execution time has been reached.
Processes due notifications without requiring manual intervention.
Safe Job Execution
Added atomic job claiming and status transitions to prevent duplicate execution.
Ensured notifications are marked as PROCESSING before delivery begins.
Integrated execution flow with the existing notification service for actual message delivery.
Downtime Recovery & Catch-Up Logic
Implemented recovery mechanisms that detect notifications missed during server downtime.
Ensured overdue notifications are processed immediately after the application becomes available again.
Prevented scheduled notifications from being lost during deployments, crashes, or restarts.
Concurrency & Scalability
Added protection against race conditions when multiple application instances are running.
Ensured a scheduled notification can only be processed by a single worker at a time.
Designed the solution to scale across distributed environments.
Failure Handling
Added structured error handling and logging.
Failed jobs are marked appropriately without interrupting processing of other scheduled notifications.
Retry tracking was implemented to improve observability and future retry strategies.
Testing
Implemented comprehensive test coverage for:
Notification scheduling and persistence
Due job discovery and execution
Status lifecycle transitions
Duplicate processing prevention
Multi-worker concurrency scenarios
Recovery after application restart
Catch-up processing for overdue notifications
Failure handling and error reporting
Result
The notification system now supports accurate future scheduling, automatic recovery after downtime, safe concurrent processing, and resilient background execution while maintaining compatibility with the existing notification delivery infrastructure.
Closes #44