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Author SHA1 Message Date
Hongming Wang
02b325063b feat(delegations): stuck-task sweeper with deadline + heartbeat-staleness rules (RFC #2829 PR-3)
Periodically scans the `delegations` table (PR-1 schema) for in-flight
rows that need terminal action:

  1. Deadline-exceeded → marked `failed` with "deadline exceeded by sweeper"
  2. Heartbeat-stale (no beat for >10× heartbeat interval) → marked `stuck`

## Why both rules

Deadline catches forever-heartbeating wedged agents (the alive-but-not-
advancing class — agent loops on heartbeat call inside its main loop).
Heartbeat-staleness catches OOM-killed and crashed agents that stop cold
without graceful shutdown. Either rule alone misses one of these classes.

## Order matters

Deadline is checked first. A deadline-exceeded AND stale row is marked
`failed` (operator action: investigate + give up), not `stuck` (operator
action: investigate + retry). The semantic difference matters.

## NULL heartbeat is a free pass

A delegation that's just been inserted but hasn't emitted its first
heartbeat yet is NOT stuck-marked — gives the agent its first beat
window. Lets the deadline catch true never-started rows naturally.

## Concurrent-completion safety

Sweep races with UpdateStatus on a delegation that just completed: the
ledger's terminal forward-only protection (PR-1) returns ErrInvalidTransition,
sweeper logs + counts in Errors, the row stays correctly in completed.

## Configuration

  - DELEGATION_SWEEPER_INTERVAL_S — tick cadence (default 5min)
  - DELEGATION_STUCK_THRESHOLD_S  — heartbeat-staleness threshold (default 10min)

Both fall back gracefully on invalid input (typo'd env shouldn't crash
startup). Both read at construction time so a long-running process
picks up overrides via restart.

## Wiring

NOT wired into main.go in this PR — that ships separately so the
sweeper can be enabled/disabled independently of the binary upgrade.
The sweeper is a standalone Sweep(ctx) callable + Start(ctx) ticker
loop, both with panic recovery, both indexed-scan-cheap on the
partial idx_delegations_inflight_heartbeat from PR-1.

## Coverage

13 unit tests against sqlmock-backed *sql.DB:

Sweep semantics (8 tests):
  - empty in-flight set → clean no-op
  - deadline → failed
  - heartbeat-stale → stuck
  - NULL heartbeat is left alone (first-beat free pass)
  - healthy row → no-op
  - both-rule row → marked failed (deadline wins)
  - mixed set → both rules fire on the right rows
  - concurrent-completion race → forward-only protection holds

Env override parsing (5 tests):
  - default on missing env
  - parses positive seconds
  - falls back on garbage
  - falls back on negative
  - constructor picks up overrides; defaults when env unset

Refs RFC #2829.
2026-05-04 20:55:13 -07:00