[HttpCache] Record age of validated and updated stale cache entries

[HttpCache] Record age of validated and updated stale cache entries

It would be good to know the correlation between an entry's age and its
likelihood to be validated vs updated. This CL adds two new metrics which
record the stale entry's age (as a percentage of freshness) when it's validated
and when it's updated.

BUG=614355
Committed: https://crrev.com/dc3cb4f7c2ca1f0ade7dcb560a8040ed2d13a695
Cr-Commit-Position: refs/heads/master@{#397720}

[jkarlin, 2016-06-03 12:17:25]

jkarlin@chromium.org changed reviewers:
+ gavinp@chromium.org, rkaplow@chromium.org

[jkarlin, 2016-06-03 12:17:25]

gavinp@ PTAL at everything
rkaplow@ PTAL at histograms.xml

Thanks!

[gavinp, 2016-06-03 14:44:05]

lgtm, although non-200s can be cached and validated...

https://codereview.chromium.org/2036123003/diff/40001/tools/metrics/histogram...
File tools/metrics/histograms/histograms.xml (right):

https://codereview.chromium.org/2036123003/diff/40001/tools/metrics/histogram...
tools/metrics/histograms/histograms.xml:17962: +    to a stale entry and is
updated (200), records the age of the entry in
Not necessarily a 200, right? Couldn't this be any other cacheable response,
like a redirect or an error? Maybe say: "typically 200" to be excrutiatingly
correct?

[jkarlin, 2016-06-03 14:51:38]

Thanks!

https://codereview.chromium.org/2036123003/diff/40001/tools/metrics/histogram...
File tools/metrics/histograms/histograms.xml (right):

https://codereview.chromium.org/2036123003/diff/40001/tools/metrics/histogram...
tools/metrics/histograms/histograms.xml:17962: +    to a stale entry and is
updated (200), records the age of the entry in
On 2016/06/03 14:44:05, gavinp wrote:
> Not necessarily a 200, right? Couldn't this be any other cacheable response,
> like a redirect or an error? Maybe say: "typically 200" to be excrutiatingly
> correct?

Good point. Done.

[rkaplow, 2016-06-03 14:59:10]

lgtm

[jkarlin, 2016-06-03 15:05:43]

The CQ bit was checked by jkarlin@chromium.org

[jkarlin, 2016-06-03 15:05:44]

The patchset sent to the CQ was uploaded after l-g-t-m from gavinp@chromium.org
Link to the patchset: https://codereview.chromium.org/2036123003/#ps60001
(title: "Address comments from PS3")

[commit-bot: I haz the power, 2016-06-03 15:06:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2036123003/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/2036123003/60001

[commit-bot: I haz the power, 2016-06-03 16:13:47]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2016-06-03 16:16:48]

Description was changed from

==========
[HttpCache] Record age of validated and updated stale cache entries

It would be good to know the correlation between an entry's age and its
likelihood to be validated vs updated. This CL adds two new metrics which
record the stale entry's age (as a percentage of freshness) when it's validated
and when it's updated.

BUG=614355
==========

to

==========
[HttpCache] Record age of validated and updated stale cache entries

It would be good to know the correlation between an entry's age and its
likelihood to be validated vs updated. This CL adds two new metrics which
record the stale entry's age (as a percentage of freshness) when it's validated
and when it's updated.

BUG=614355

Committed: https://crrev.com/dc3cb4f7c2ca1f0ade7dcb560a8040ed2d13a695
Cr-Commit-Position: refs/heads/master@{#397720}
==========

[commit-bot: I haz the power, 2016-06-03 16:16:49]

Patchset 4 (id:??) landed as
https://crrev.com/dc3cb4f7c2ca1f0ade7dcb560a8040ed2d13a695
Cr-Commit-Position: refs/heads/master@{#397720}