Increase static assets cache max-age for improved performance

[cdrini]

Feature Request

Problem / Opportunity

Pagespeed Insights recommends improving cache lifetimes for our static assets to save an estimated 272 KiB and speed up repeat visits. Currently, many assets (images, SVGs, covers, etc.) have cache TTLs of only 1-3 hours, which is much shorter than it could be.

A long cache lifetime can make Open Library pages load faster for users, especially those accessing frequently-used resources such as covers and UI images.

Reference analysis: Pagespeed Insights result

Justification

Implementing proper caching headers for static assets can reduce transfer size, lower server overhead, and improve perceived speed for users.

Breakdown

Related files

• Static asset handlers (image, CSS, SVG, GIF uploads) ; not sure where the code for where this happens in the local environment is.
• in prod, static assets come from here:

  openlibrary/docker/web_nginx.conf

  Lines 155 to 177 in bec96c4

  	location ~ ^/(images/.*|favicon.ico|robots.txt)$ {
  	rewrite ^(.*)$ /static/$1 last;
  	}
  	location ~ ^/(y_key_[0-9a-f]+.html|LiveSearchSiteAuth.xml)$ {
  	root /olsystem/www;
  	}
  	location ~ ^/static/(docs|tour|sitemaps|jsondumps|images/shelfview|sampledump.txt.gz)(/.*)?$ {
  	root /sitemaps;
  	autoindex on;
  	rewrite ^/static/(.*)$ /$1 break;
  	}
  	location /static {
  	autoindex on;
  	expires 1h;
  	}
  	location /static/build {
  	expires max;
  	}

• Covers; see

  openlibrary/openlibrary/coverstore/code.py

  Lines 271 to 282 in f362492

  	if key == 'id':
  	etag = f"{d.id}-{size.lower()}"
  	if not web.modified(trim_microsecond(d.created), etag=etag):
  	return web.notmodified()
  	web.header('Cache-Control', 'public')
  	# this image is not going to expire in next 100 years.
  	web.expires(100 * 365 * 24 * 3600)
  	else:
  	web.header('Cache-Control', 'public')
  	# Allow the client to cache the image for 10 mins to avoid further requests
  	web.expires(10 * 60)

  . It seems like this is trying to set it to 100 years with web.expires, but it doesn't appear to be working.

May need to audit current asset serving and add Cache-Control headers or similar to extend cache lifetime for images and other static resources.

Stakeholders

@RayBB

[mekarpeles]

Related to

• No Cache-Control headers on IA CDN requests #8927
• Increase expiry date / maximum age for static resources to 1 day #1367