Pre-warming connection pool

CHANGELOG.md

@@ -27,7 +27,7 @@ Changes can also be flagged with a GitHub label for tracking purposes. The URL o
 - Added location filter to new request manager screen [#7132](https://github.com/ethyca/fides/pull/7132)
 - Added handling for "page-level" errors [#7144](https://github.com/ethyca/fides/pull/7144)
 - Added sorting to new request manager screen [#7138](https://github.com/ethyca/fides/pull/7138)
-
+- Pre-warming the async DB pool on server startup [#7141](https://github.com/ethyca/fides/pull/7141)
 
 ### Changed
 - Bulk privacy request actions now accept filter sets as well as lists, enables select all functionality. [#7027](https://github.com/ethyca/fides/pull/7027)

src/fides/api/db/ctl_session.py

@@ -1,7 +1,9 @@
+import asyncio
 import ssl
 from typing import Any, AsyncGenerator, Dict
 
-from sqlalchemy import create_engine
+from loguru import logger
+from sqlalchemy import create_engine, text
 from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
 from sqlalchemy.orm import sessionmaker
 
@@ -64,3 +66,42 @@ async def get_async_db() -> AsyncGenerator:
     """Return an async session generator for dependency injection into API endpoints"""
     async with async_session() as session:
         yield session
+
+
+async def warmup_async_pool() -> None:
+    """
+    Warm up the async connection pool by pre-creating connections.
+
+    This function creates up to pool_size connections concurrently and executes
+    a simple query on each to ensure they are fully established and validated.
+    This reduces latency for the first requests after server startup.
+    """
+
+    pool_size = CONFIG.database.api_async_engine_pool_size
+    if pool_size <= 0:
+        logger.debug("Skipping async pool warmup: pool_size is 0")
+        return
+
+    logger.info(
+        "Warming up async connection pool (creating {} connections)...", pool_size
+    )
+
+    async def create_and_validate_connection() -> None:
+        """Create a single connection and validate it with a query."""
+        try:
+            async with async_session() as session:
+                await session.execute(text("SELECT 1"))
+        except Exception as exc:
+            logger.warning("Failed to create connection during pool warmup: {}", exc)
+            # Don't re-raise - we want to continue warming up other connections
+
+    try:
+        # Create all connections concurrently
+        await asyncio.gather(
+            *[create_and_validate_connection() for _ in range(pool_size)],
+            return_exceptions=True,
+        )
+        logger.info("Async connection pool warmup completed successfully")
+    except Exception as exc:
+        logger.error("Error during async pool warmup: {}", exc)
+        # Don't raise - pool will still work, just without pre-warmed connections

src/fides/api/main.py

@@ -33,6 +33,7 @@
 )
 from fides.api.common_exceptions import MalisciousUrlException
 from fides.api.cryptography.identity_salt import get_identity_salt
+from fides.api.db.ctl_session import warmup_async_pool
 from fides.api.middleware import handle_audit_log_resource
 from fides.api.migrations.hash_migration_job import initiate_bcrypt_migration_task
 from fides.api.migrations.post_upgrade_index_creation import (
@@ -89,6 +90,8 @@ async def lifespan(wrapped_app: FastAPI) -> AsyncGenerator[None, None]:
 
     await run_database_startup(wrapped_app)
 
+    await warmup_async_pool()
+
     check_redis()
 
     if not scheduler.running: