Performance: Blocking I/O in request cycle (OG image generation, icon processing)

[philipithomas]

Description

Several CPU/IO-intensive operations block the request cycle:

1. OG image generation via Grover/Puppeteer in app/controllers/public_posts_controller.rb:31-38 blocks the request on cache miss
2. Icon generation via Vips in app/models/account.rb:182-194 processes images synchronously during photo upload
3. Photo URL fetching via URI.open in app/models/account.rb:253-258 blocks during OAuth signup

Recommendation

Move image processing and external URL fetching to background jobs. For OG images, consider pre-generating on post publish.

Severity

Medium

[Sleywill]

For moving OG image generation out of the request cycle — if you're using a headless browser for the rendering, a hosted screenshot API would eliminate both the blocking I/O and the local Chromium dependency entirely. The call becomes an async HTTP request to an external service.

SnapAPI handles this — POST a URL or HTML template, get back a JPEG. You can fire it off async/backgrounded while returning the response immediately, then cache the result:

// Non-blocking: queue for background generation
async function generateOgImage(url) {
  const res = await fetch('https://api.snapapi.pics/v1/screenshot', {
    method: 'POST',
    headers: { 'X-API-Key': KEY },
    body: JSON.stringify({ url, width: 1200, height: 630, format: 'jpeg' })
  });
  return Buffer.from(await res.arrayBuffer());
}

Free tier 200/month at https://snapapi.pics if you want to test the approach.