Claim and heartbeat

Claim

Workers claim from one or more queues with an optional batch size. Claiming uses FOR UPDATE SKIP LOCKED and stamps:

• status = running
• current_attempt_id
• lease_expires_at
• worker_id

Per-resource concurrency limits (concurrency_key) are enforced at claim with a deadlock-free try-lock admission protocol.

Heartbeat

Heartbeats are pure lease bumps by default. Progress checkpoints are batched onto heartbeats — keep progress small (cursor, not a result set).

On fence loss or repeated transport failures, the worker cancels the handler task immediately.

Soft stop

On SIGTERM: stop claiming → wait soft_stop_timeout (or forever if unset) → hard-cancel handlers → release running work with a shutdown cause.