Common caching worker not caching requests using HEAD method

[alxbridge]

It appears that all requests sent using the HEAD method are passed on to the backend servers, which can make a site easy to overload with a flurry of this type of request.

According to Cloudflare's docs,

cache.put will throw an error if:

• The request passed is a method other than GET.

This is in contrast with Cloudflare's default behaviour for caching HEAD requests:

When you make a HEAD request for a cacheable resource and Cloudflare does not have that resource in the edge cache, a cache miss happens. Cloudflare will send a GET request to your origin, cache the full response and return the response headers only.

To verify this behaviour on a site using the worker, compare the cf-cache-status header returned for a request made with GET:

curl -v [URL] 2>&1 | grep "cf-cache-status"
# < cf-cache-status: HIT - at least from the second request onwards

with the same request made with HEAD:

curl --head -v [URL] 2>&1 | grep "cf-cache-status"
# < cf-cache-status: DYNAMIC - always