req.hash_ignore_busy

BOOL, can be read and set, but not unset.

Available inrecv

When there is more than one simultaneous cache miss for an object, Varnish will normally put all but one of the threads handling those requests to sleep. Thus, only one cache miss hits the origin and the rest wait for that response. req.hash_ignore_busy overrides this behavior and lets all requests through simultaneously.

Try it out

req.hash_ignore_busy is used in the following solution recipes, which show real world use cases. Click RUN to provision a Fastly service, execute the code on Fastly, and see how the function behaves.

Cache '429' rate-limiter responses per IP

If a backend returns a 429, cache it for the requesting IP but continue to allow other clients to use origin.

User contributed notes

We welcome comments that add use cases, ideas, tips, and caveats. All comments will be moderated before publication. To post support questions, visit our support center and we'll find you the help you need.