- From: Alex Rousskov <rousskov@measurement-factory.com>
- Date: Mon, 10 Sep 2018 10:13:36 -0600
- To: ietf-http-wg@w3.org
On 09/07/2018 12:44 AM, Mark Nottingham wrote: > FYI; IMO it's past time to standardise x-cache and have a real spec for it. > > This is a straw-man, based on a bit of research on existing implementations. > > Pretty version at: > https://mnot.github.io/I-D/cache-header/ > > Comments? I think the primary audience here is proxy cache and CDN > vendors, and their users. If we are to standardize X-Cache, then we should be mindful of the trap created by early implementations that thought a single action value can adequately relay what has happened at the proxy: 1. The obvious HIT and MISS actions came first. 2. Then we quickly discovered that a "we found it in the cache" HIT action is often followed by a REFRESH action (and a resulting MISS from the proxy-server traffic point of view). HIT_REFRESH... concatenations were used to combat this. 3. Realizing that even fresh cache HITs may become misses due to various protocol requirements and internal problems, some added X-Cache-Lookup that was dedicated to the first (and often critical for triage) cache lookup, depicting what happened to that HIT later in X-Cache. 4. Then flash crowds and collapsed forwarding solutions came along. Now, a single client HIT or MISS request could cause even more transactions, some of which could be cache hits, some could be revalidations or even errors. Some added COLLAPSED_HIT_REFRESH... and/or other variants. This concatenation approach still loses a lot of info, but it highlights the fact that a lot of info could be lost by including the COLLAPSED tag. If the goal here is to standardize the current status quo, then the document should cover Cache-Lookup and COLLAPSED tags (and/or their variations). If the goal here is to standardize a scalable solution based on the current experience, then we should combine Cache-Lookup and Cache while enumerating individual cache actions as separate same-node entries (instead of trying to merge them into a single FOO_BAR_BAZ super-action summary for one node). Cheers, Alex.
Received on Tuesday, 11 September 2018 06:33:59 UTC