ObjectReplicationBackfillService

Info

Scheduled service for bulk backfilling legacy objects across storage providers and replaying dead-lettered replication tasks.

Overview

ObjectReplicationBackfillService performs two scheduled operations: (1) scanning existing database records (user avatars, wallpaper assets, issue feedback) and enqueuing replication tasks for objects that haven't been replicated yet, and (2) replaying DLQ tasks back to the processing queue.

Scheduled Tasks

Task	Interval Config	Default	Description
backfillLegacyResources()	object-replication.backfill-interval-ms	5000	Scan and enqueue legacy objects
replayDlqTasks()	object-replication.dlq-replay-interval-ms	15000	Replay dead-lettered tasks

Backfill Scopes

Scope	Checkpoint Key	Source Table	Fields Replicated
User Avatars	backfill_user_avatar	User table	avatar URL
Wallpaper Assets	backfill_wallpaper_asset	Wallpaper table	originalUrl, thumb320Url, thumb720Url, thumb1280Url
Issue Feedback	backfill_issue_feedback	Feedback table	feedbackLogUrl, feedbackScreenshotUrl

Checkpoint System

Each backfill scope tracks progress via object_replication_checkpoint:

Field	Description
checkpointKey	Scope identifier
lastId	Last processed row ID
status	pending / running / done

Resumes from lastId on restart; marks done when no more rows are found.

URL Resolution

The service resolves source URLs to StorageUploadResult by matching against all configured provider domains and endpoints:

• R2: public domain, endpoint+bucket, *.r2.dev
• OSS: custom domain, virtual-host style
• COS: custom domain, default host ({bucket}.cos.{region}.myqcloud.com)

Configuration

Property	Default	Description
object-replication.backfill-enabled	false	Enable backfill scanning
object-replication.backfill-batch-size	200	Rows per batch
object-replication.dlq-replay-enabled	false	Enable DLQ replay
object-replication.dlq-replay-batch-size	100	Tasks per replay batch

Warning

Both backfill and DLQ replay are disabled by default. Enable them explicitly during migration windows.