Reduce db conn pool size and increase max conns (#630)

Author: petebachant

.gitignore

@@ -6,3 +6,5 @@ node_modules/
 /playwright/.cache/
 .env
 .DS_Store
+TODO.md
+AGENTS_files

backend/app/db.py

@@ -21,8 +21,11 @@
 max_tries = 60 * 5  # 5 minutes
 wait_seconds = 1
 
+# Each worker process gets its own pool, so keep per-process limits modest:
+# with 12 workers (8 backend + 4 backend-dvc), 5 + 5 = 10 per process gives a
+# 120-connection worst case, comfortably under the db's max_connections (300).
 engine = create_engine(
-    str(settings.SQLALCHEMY_DATABASE_URI), pool_size=10, max_overflow=10
+    str(settings.SQLALCHEMY_DATABASE_URI), pool_size=5, max_overflow=5
 )
 
 # make sure all SQLModel models are imported (app.models) before initializing DB

docker-compose.yml

@@ -2,6 +2,9 @@ services:
   db:
     image: postgres:16
     restart: always
+    # Raise the default max_connections (100) to accommodate per-worker
+    # connection pools across all backend processes. See backend/app/db.py.
+    command: ["postgres", "-c", "max_connections=300"]
     healthcheck:
       test: ["CMD-SHELL", "pg_isready -U ${POSTGRES_USER} -d ${POSTGRES_DB}"]
       interval: 10s