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By default Odoo bundles static assets (JS and CSS) within a couple of files: All CSS files are bundled into a single big CSS file. The same happens for JS files.

The URLs of those bundles vary with any change within any of the included files. But those files are big. Therefore changing assets put some stress in the network and diminish the usefulness of caches.

Since Sep 19th, 2015 we introduced a patch in Odoo to avoid bundling of static assets when using a SPDY or HTTP/2 proxy like Nginx.

Reportedly, this has worked very well in our case where some users have slow connections. However, measuring the logs of a week we see that about 21% of GET request are assets:

$ egrep 'GET .*(\.|/)(css|js).* HTTP/' /var/log/nginx/o.access.log.1 | wc -l
10554

$ egrep 'GET .* HTTP' /var/log/nginx/o.access.log.1 | wc -l
50216

Odoo’s default cache expiration time is seven days. This is considerably low taking into account that bundle’s URLs change when the content does.

Another issue is that assets that change can be served staled from the caches for seven days.

We’re taking the path to produce unique URLs for static assets. Our current work can be seen in our merchise-unique-static-urls branch. In our development/deployment scenarios these simple changes would suffice for JS and CSS. There’s still work to do regarding invalidation of static images in our templates.