BBlack added a comment.
In https://phabricator.wikimedia.org/T125392#1994242, @Milimetric wrote:
> @BBlack - so you think cache_status is not even close to accurate? Do we
> have other accurate measurements of it so we could compare to what extent
> it's misleading? I'm happy to remove it from the data if it's really bad.
On this topic, it is pretty misleading, and we do have other stats we look at
more-manually to compare. We don't have a good singular, simple replacement
for cache_status to include in analytics yet, though. What we do have (that
we've looked at manually in some cases lately) is the `X-Cache` response
header. That header has evolved a bit in how it's generated over the past
couple of months so that it's less-misleading than it was before, but it still
requires various regex operations to bin responses according to what exactly
one is trying to measure. But for an example, this pseudo-code would be an
accurate way to put all requests into 3 distinct non-overlapping bins based on
X-Cache regex:
if (X-Cache ~ / hit/) {
print "This is a real cache object hit";
}
else if (X-Cache ~ / int/) {
print "This response was generated internally by varnish (e.g. 301
redirect for HTTPS, desktop->mobile redirect on UA detect, some kinds of error
response, etc)";
}
else {
print "This is a cache miss or a cache pass (pass would be due to
uncacheable content, which is more-often true for loggedin users than others,
but exists in both cases in notable numbers)";
}
However, I think X-Cache's raw data is still open to further modification.
Ideally we'll build on top of this and start emitting some standard, simple
header that can be one of N simple strings and reflects overall cache status
bins (and hopefully with better detail as to miss-vs-pass and the nature of the
pass to some degree).
TASK DETAIL
https://phabricator.wikimedia.org/T125392
EMAIL PREFERENCES
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To: Addshore, BBlack
Cc: JanZerebecki, Milimetric, BBlack, ori, gerritbot, hoo, daniel, Aklapper,
Addshore, Lydia_Pintscher, Izno, Wikidata-bugs, aude, Mbch331
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