724188 - Do not cache XHR responses unless they have explicit cache-control headers

Status: RESOLVED WONTFIX

(Core :: Networking: HTTP, defect)

Description

[Brian Smith (:briansmith, :bsmith, use NEEDINFO?)]

Recently, we hypothesized that most XHR responses are probably not worth caching. I think that, absent a really strong indicator that we should cache an XHR response, we should throw them away by default.

I suggest we design a couple of policies (e.g. "no heuristic caching for XHR", "only cache XHR in memory"), and then design and deploy some telemetry that tells us what the difference in cache hit rate and the difference in replaced-without-a-hit would be, before we make the actual change.

Comment 1

[Patrick McManus [:mcmanus]]

there have been a number of cases where people expect just the opposite. Its critical that we honor no-cache on the request side tho (different bug)