Only render an image when it's first requested by a browser. Fixes #455
Detailed description
Instead of immediately scheduling images for rendering at page-render time, this shoves the render request into an unwieldy, grotesquely-long URL that encodes the render request state, and then the _async image handler is responsible for generating the render request from that.
This uses signed URLs to avoid situations where someone may construct a malicious render request externally. The downside is that in a load-balanced scenario, this requires that all backing instances use the same app.secret_key or that the load balancer provides strong connection affinity, but that's currently the case for all user authentication as well.
Developer/user impact
There should be no impact on users, aside from some edge cases where images will fail to load if a page is requested immediately before a Publ deployment occurs but before the images get rendered.
Test plan
Unit tests continue to pass, and manually removed the tests/static/_img directory to smoke-test various scenarios.
Summary
Only render an image when it's first requested by a browser. Fixes #455
Detailed description
Instead of immediately scheduling images for rendering at page-render time, this shoves the render request into an unwieldy, grotesquely-long URL that encodes the render request state, and then the
_asyncimage handler is responsible for generating the render request from that.This uses signed URLs to avoid situations where someone may construct a malicious render request externally. The downside is that in a load-balanced scenario, this requires that all backing instances use the same
app.secret_keyor that the load balancer provides strong connection affinity, but that's currently the case for all user authentication as well.Developer/user impact
There should be no impact on users, aside from some edge cases where images will fail to load if a page is requested immediately before a Publ deployment occurs but before the images get rendered.
Test plan
Unit tests continue to pass, and manually removed the
tests/static/_imgdirectory to smoke-test various scenarios.Got a site to show off?