Daniel Sutton
139eede41c
## Summary Adds `drainBatchSize` to `MollifierDrainer` (default `1` — preserves existing behaviour) and wires `TRIGGER_MOLLIFIER_DRAIN_BATCH_SIZE` through the webapp (default `50`). Each tick the drainer now pops up to `drainBatchSize` from each chosen env, then dispatches every popped entry through the shared `concurrency`-bounded `pLimit`. Per-org/per-env fairness is unchanged — only the in-env pop count grows. Pre-existing behaviour was one pop per env per tick. For a single-env burst that single-flighted the drain at the per-tick floor of `pop + engine.trigger ≈ 50–60 ms`. With buffer entries piling up under a real-world tenant burst that's tens of minutes of tail latency to fully materialise — even though PG itself could comfortably sustain the writes. ## Why this matters — heavy-tail illustration Scenario: 100 customers in one window — 94 fire 20 triggers each, 5 fire 100, 1 fires 1000. Gate at `THRESHOLD=10/s`, `HOLD_MS=500`. First 10 of each burst hit PG directly; the rest buffer. | Customers | Triggers each | PG direct | Buffered each | Total buffered | |---|---|---|---|---| | 94 small | 20 | 10 | 10 | 940 | | 5 medium | 100 | 10 | 90 | 450 | | 1 heavy | 1000 | 10 | 990 | 990 | **With `DRAIN_BATCH_SIZE=50`, `DRAIN_CONCURRENCY=50`, ~50 ms `engine.trigger`:** | Tick | Pops | Dispatch waves | Wall-clock | |---|---|---|---| | 1 | 94×10 + 5×50 + 1×50 = 1 240 | 25 × 50 ms | ~1 300 ms (94 smalls done) | | 2 | 5×40 + 1×50 = 250 | 5 × 50 ms | ~300 ms (5 mediums done) | | 3–20 | heavy alone, 50/tick | 1 × 50 ms | ~100 ms each | | Customer class | Buffered fully drained | |---|---| | 94 small | **~1.3 s** | | 5 medium | **~1.6 s** | | 1 heavy | **~3.4 s** | **Without batching (one pop per env per tick — current behaviour):** | Customer class | Buffered fully drained | |---|---| | 94 small | ~500 ms | | 5 medium | ~4.5 s | | 1 heavy | **~49 s** | So the heavy single-tenant tail drops from ~49 s to ~3.4 s (~14× faster) without changing PG load characteristics. Smalls go up slightly in this scenario (500 ms → 1.3 s) because all 100 envs share one tick's dispatch queue — that's the trade we accept for the heavy tail; the worst-case small wait is still inside one tick. PG load is identical either way (50 concurrent inserts at a time, capped by `DRAIN_CONCURRENCY`). ## What changed **`packages/redis-worker`** - New `drainBatchSize` option (default 1 — full backward compat). - `runOnce()` refactored to pop per-env batches in parallel, then dispatch all popped entries through the existing global `pLimit`. Mid-batch pop failure aborts only that env's batch and counts as one failure (same semantic as the old per-env path). - Removed the now-unused `processOneFromEnv` helper. **`apps/webapp`** - `TRIGGER_MOLLIFIER_DRAIN_BATCH_SIZE` env var (default 50, matching `DRAIN_CONCURRENCY`). - Wired into `mollifierDrainer.server.ts`. **Test cloud config** (separate cloud PR): `TRIGGER_MOLLIFIER_DRAIN_BATCH_SIZE="50"` on the worker service. Production rollout deferred until we've watched it on test cloud. ## Test plan - [x] All 25 stub-based drainer tests pass (18 pre-existing + 7 new). 7 new tests under `MollifierDrainer.drainBatchSize`: - pops up to `drainBatchSize` across ticks - global `concurrency` cap still holds when batch > concurrency - mid-batch pop failure isolation - multi-env batch fan-out in one tick - **hierarchical org fairness preserved at `drainBatchSize > 1`** (load-bearing — guards against future regressions to per-env-instead-of-per-org rotation) - mixed success/failure accounting in a batched tick - bounded pops on empty queue (no Lua spam past `drainBatchSize`) - [x] All pre-existing tests still pass unchanged at default `drainBatchSize=1` → backward-compat locked. - [x] `pnpm run build --filter @trigger.dev/redis-worker` clean. - [x] `pnpm run typecheck --filter webapp` clean. - [x] `redisTest` block (real Redis via testcontainers) — couldn't run locally on this branch due to testcontainers runtime discovery; will validate in CI. - [ ] Test-cloud smoke after cloud PR lands: fire `burst 50` against a flagged env and confirm the 50th entry's drain time drops from ~2.5 s to <200 ms. ## Notes - Per-tick memory bound: `maxOrgsPerTick × drainBatchSize` entries can sit in the JS pLimit queue between pop and dispatch. At defaults that's `500 × 50 = 25 000` × ~5 KB snapshot ≈ ~125 MB worst case per worker — well within headroom. - The pre-batch model's strict per-env throughput cap of `1/tick` is documented as the fairness baseline elsewhere. Org-level fairness is what callers actually rely on; this change does not weaken that. 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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