Pre-warming connection pool

[galvana]

Description Of Changes

Pre-warming async connection pool to prevent expensive type introspection on first connection usage. Local performance tests showed the type introspection taking up to 7 seconds on a busy database. This thread suggests disabling jit but we figured that's a change we'd want to run a broader performance test for.

Steps to Confirm

1. The server should start up. You'll see this in the server-startup logs

Async connection pool warmup completed successfully

Pre-Merge Checklist

• Issue requirements met
• All CI pipelines succeeded
• CHANGELOG.md updated
  • Add a db-migration This indicates that a change includes a database migration label to the entry if your change includes a DB migration
  • Add a high-risk This issue suggests changes that have a high-probability of breaking existing code label to the entry if your change includes a high-risk change (i.e. potential for performance impact or unexpected regression) that should be flagged
  • Updates unreleased work already in Changelog, no new entry necessary
• UX feedback:
  • All UX related changes have been reviewed by a designer
  • No UX review needed
• Followup issues:
  • Followup issues created
  • No followup issues
• Database migrations:
  • Ensure that your downrev is up to date with the latest revision on main
  • Ensure that your downgrade() migration is correct and works
    • If a downgrade migration is not possible for this change, please call this out in the PR description!
  • No migrations
• Documentation:
  • Documentation complete, PR opened in fidesdocs
  • Documentation issue created in fidesdocs
  • If there are any new client scopes created as part of the pull request, remember to update public-facing documentation that references our scope registry
  • No documentation updates required

[vercel]

Deployment failed with the following error:

You must set up Two-Factor Authentication before accessing this team.

View Documentation: https://vercel.com/docs/two-factor-authentication

[greptile-apps]

Greptile Overview

Greptile Summary

Pre-warms the async connection pool during server startup to prevent expensive type introspection (up to 7 seconds) on first connection usage. The warmup creates connections up to pool_size (default 50) concurrently and validates each with a simple query.

• Added warmup_async_pool() function in src/fides/api/db/ctl_session.py:71-107 that creates connections concurrently using asyncio.gather
• Integrated into server startup lifecycle in src/fides/api/main.py:93 after database startup and before Redis check
• Includes graceful error handling with warnings for individual connection failures
• Found one logic issue: asyncio.gather() needs return_exceptions=True to properly handle all connection failures without stopping the warmup process

Confidence Score: 4/5

• This PR is safe to merge with one minor fix needed for exception handling
• The implementation is sound with proper logging, graceful error handling, and appropriate placement in the startup sequence. However, the asyncio.gather() call needs return_exceptions=True to properly continue warming up connections even if some fail, which is the intended behavior based on the comments
• src/fides/api/db/ctl_session.py requires a one-line fix to add return_exceptions=True parameter

Important Files Changed

File Analysis

Filename	Score	Overview
src/fides/api/db/ctl_session.py	4/5	Added async connection pool warmup function to pre-create connections and reduce type introspection latency. Minor issue with exception handling in asyncio.gather.
src/fides/api/main.py	5/5	Called warmup_async_pool during server startup lifespan, positioned appropriately after database startup and before Redis check.

[greptile-apps]

_{2 files reviewed, 1 comment}

_{Edit Code Review Agent Settings | Greptile}

[johnewart]

👍 Should we do the same for the synchronous pool at some point?

[erosselli]

Approved, let's add a changelog

[codecov]

Codecov Report

❌ Patch coverage is 77.27273% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.29%. Comparing base (c8af6ca) to head (62e5e04).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/fides/api/db/ctl_session.py	75.00%	4 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7141      +/-   ##
==========================================
- Coverage   87.30%   87.29%   -0.01%     
==========================================
  Files         533      533              
  Lines       35095    35116      +21     
  Branches     4067     4068       +1     
==========================================
+ Hits        30640    30656      +16     
- Misses       3570     3574       +4     
- Partials      885      886       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.