[argus] patch #39: bound the checkpointer pool (elastic 1..4, idle-shrink)#4
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…, idle-shrink) psycopg_pool's default is a fixed pool: max_size falls back to min_size=4, so every uvicorn worker permanently holds 4 idle Postgres connections. With 2 workers per gateway and one gateway per project stack, that idle floor alone exhausted the shared server's max_connections on 2026-07-01 (FATAL: sorry, too many clients already). Keep the same per-worker ceiling (4) but make the pool elastic: min_size=1, grow under load, shrink back after max_idle=300s. Deployment overrides via DEERFLOW_CHECKPOINTER_POOL_MIN / _MAX / _MAX_IDLE. Keepalive kwargs and check_connection wiring unchanged. Tests: tests/test_checkpointer_pool_bounds.py pins the defaults, the env overrides, and the keepalive/check wiring (psycopg faked via sys.modules, no live Postgres needed). 207 green across the checkpointer-touching suites; ruff clean on changed files. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Why
psycopg_pool's default is a fixed pool:
max_sizefalls back tomin_size=4, so every uvicorn worker permanently holds 4 idle Postgres connections. With 2 workers per gateway and one gateway per project stack, the idle floor alone (10 conns per stack, observed exactly) exhausted the shared server'smax_connectionson 2026-07-01 (FATAL: sorry, too many clients already, hit twice that day). Raisingmax_connectionsto 500 bought headroom; this bounds the actual source.What
_build_postgres_pool()(the single pool-construction site, used by both the legacycheckpointer:and unifieddatabase:config paths) now passes:min_size=1(was: implicit 4)max_size=4(same ceiling as today's default, now explicit)max_idle=300seconds, so the pool shrinks back to min after idleEach is overridable per deployment via
DEERFLOW_CHECKPOINTER_POOL_MIN/_MAX/_MAX_IDLE. Keepalive kwargs andcheck_connectionwiring are unchanged. Expected effect on argus: per-gateway idle baseline drops from 10 to ~2 while burst capacity stays identical.Tests
backend/tests/test_checkpointer_pool_bounds.pypins the defaults, the env overrides, and the keepalive/check wiring (psycopg faked viasys.modules, no live Postgres needed). 207 passed / 1 skipped across all checkpointer-touching suites locally; ruff clean on changed files. Note:lint-backendandfrontend-unit-testsCI jobs are red on pre-existing debt (same as patches bytedance#37/bytedance#38).Deploy (post-merge, separate step)
App-code change: pin bump in argus VERSIONS.md +
make deerflow-upgrade+ restart stacks canary-first. Rollback = revert pin to2df36c9.🤖 Generated with Claude Code