Questions on metrics returned

[nathanziarek]

• I'm looking at the metrics returned from the REST API in a JSON response. I'm noticing the sometimes a metric (such as score_cache) is "0", while other times it's "-1". In both cases the item could be cached.
• Every item under the "requests" array gives a "score_combine" of -1, but the overall score is 100. On this particular site, we load over 20 JS files on each page load, so we should fail that test pretty thoroughly!
• What is score_cookies? I would have thought it was similar to score_cdn (i.e. keeping static objects on a cookie-less domain).
• What is image_total and why is it 0?
• I know I can smush some of my images smaller, but image_savings is also 0.
  

[pmeenan]

-1 generally means N/A (for caching that means the resource was probably marked as no-cache) while 0 means it should have been cacheable but failed.

As far as combine goes, I'm not sure that I'm calculating that anymore and it should be removed from the results (I'll look into it). There's a lot of subtlety about head resources vs late-body resources and HTTP/2 that make resource combining a more complicated topic.

- score_cookies is also somewhat deprecated but it checks to see if cookies were sent up for static resources. It's from the days where it was advisable to serve static resources from a separate cookie-less domain.

The image checks (total and savings) are only checking JPEG images for lossy compression right now so if you have PNG images that could be better smushed it isn't picking them up.