Size the Connection Pool to Avoid Exhaustion
Set the pool max to twice the CPU cores and add a acquire timeout so a spike does not exhaust connections and queue forever.
Task
Apply const pool = createPool({ max: 2 * os.cpus().length, acquireTimeoutMillis: 5000 }); to reduce a measured bottleneck that shows up in the performance budget or Lighthouse audit.
When to use this
Lighthouse reports the page fails the performance budget because of const pool = createPool({ max: 2 * os.cpus().length, acquireTimeoutMillis: 5000 });, scoring 72 on mobile.
Prerequisites
- A Lighthouse or WebPageTest baseline measurement
- Access to the build configuration
Steps
1. Configure const pool = createPool({ max: 2 * os.cpus().length, acquireTimeoutMillis: 5000 }); in the project configuration file with the recommended defaults.
const pool = createPool({ max: 2 * os.cpus().length, acquireTimeoutMillis: 5000 });
Expected output: The configuration is accepted and const pool = createPool({ max: 2 * os.cpus().length, acquireTimeoutMillis: 5000 }); runs without errors on the first invocation.
2. Run the check locally to verify const pool = createPool({ max: 2 * os.cpus().length, acquireTimeoutMillis: 5000 }); produces the expected result before pushing.
pnpm test
Expected output: Local run matches CI behavior; no surprises after push.
3. Add the gate to the CI pipeline so const pool = createPool({ max: 2 * os.cpus().length, acquireTimeoutMillis: 5000 }); blocks merge on failure.
- name: Run add connection pool sizing
run: pnpm test
Expected output: Pull requests with failing const pool = createPool({ max: 2 * os.cpus().length, acquireTimeoutMillis: 5000 }); are blocked from merging.
Troubleshooting
Problem
The check passes locally but fails in CI
Solution
Pin dependency versions and the runtime to match CI exactly; reproduce with the same Docker image or act.
Problem
Configuration is rejected with a schema error
Solution
Check the tool version matches the config schema; older versions may not support newer fields.
Limitations
- The gate only runs on events that trigger the workflow; locally pushed commits bypass it.
- Configuration drift is possible if someone edits settings outside version control.
Measure before optimizing
Start by measuring the problem. Set the pool max to twice the CPU cores and add a acquire timeout so a spike does not exhaust connections and queue forever. The most common mistake is adding the gate without first confirming it catches the issue you care about. Run const pool = createPool({ max: 2 * os.cpus().length, acquireTimeoutMillis: 5000 }); against the current codebase and inspect the output before wiring it into CI.
const pool = createPool({ max: 2 * os.cpus().length, acquireTimeoutMillis: 5000 });Verify the improvement
Once the gate is in place, make failures actionable. A failing const pool = createPool({ max: 2 * os.cpus().length, acquireTimeoutMillis: 5000 }); should point to the exact file and line, not a generic error. Pin the tool version in the lockfile so a upstream release does not silently change behavior. Review the gate output in every pull request just like a test result.