The single serial DeliveryWorker is replaced by Infrastructure/Jobs:
- Job rows are leased with one FindOneAndUpdate (oldest RunAt first, a
two-minute lease) and a reaper returns expired leases every 30 s;
- enqueueing wakes the workers, which otherwise poll every five seconds;
- delivery runs eight at a time with at most two per host, so a slow or
dead server holds two slots, not the queue;
- a failure waits n^4 + 15 + jitter seconds (Mastodon's curve) for up to
16 attempts; a 4xx other than 408/429 is final, a 429 honours
Retry-After;
- RemoteInstance is a per-host circuit breaker: ten consecutive failures
quarantine a host for an hour, doubling to a week, and its jobs wait
without spending attempts;
- a delivery is queued once per activity and inbox (unique DedupeKey), and
finished jobs expire after seven days (TTL on FinishedAt).
Migration _004 moves pending Delivery rows into jobs and marks them
abandoned, so a rollback to the old worker cannot send them twice.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012CzABvBkbcFqoHdmi8b9WB
thepraandClaude Opus 5.5
d1a91c40c4