2072119 - Improve DNS negative caching: make the lifetime a pref and add cache-miss telemetry

Status: RESOLVED FIXED

(Core :: Networking: DNS, task, P2)

Description

[Kershaw Chang [:kershaw]]

HE resolves A and AAAA as separate per-family lookups, so an empty/NODATA AAAA answer is cached as a negative record.
Once that negative AAAA entry is gone, HE must do a fresh blocking AAAA lookup while the A record is still a warm hit, and wait_for_preferred_address holds the connection for up to network.http.happy_eyeballs_resolution_delay. The legacy AF_UNSPEC path does not split families and caches the (positive) result for the full TTL, so it is unaffected.

Two problems, addressed together here:

1. We can't tell why the AAAA entry was gone because the telemetry doesn't distinguish expired or evicted, nor negative records, nor address family.
2. The negative-cache lifetime is a hardcoded 60s constant.

Comment 1

[Kershaw Chang [:kershaw]]

Attachment: Bug 2072119 - Add telemetry for why DNS lookups miss the cache r?#necko

Comment 2

[Kershaw Chang [:kershaw]]

Attachment: Bug 2072119 - Make the DNS negative-cache lifetime a pref and raise the default r?#necko

Depends on D326128

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/ee62863169fc
https://hg.mozilla.org/integration/autoland/rev/b5fdb1a9b960
Add telemetry for why DNS lookups miss the cache r=necko-reviewers,valentin,mxinden
https://github.com/mozilla-firefox/firefox/commit/f87b4b438bf0
https://hg.mozilla.org/integration/autoland/rev/b70b40bdf2a2
Make the DNS negative-cache lifetime a pref and raise the default r=necko-reviewers,valentin

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/04e912057237
https://hg.mozilla.org/integration/autoland/rev/101ff7b48bf5
Revert "Bug 2072119 - Make the DNS negative-cache lifetime a pref and raise the default r=necko-reviewers,valentin" for causing multiple Gtest failures

Comment 5

[Norisz Fay [:noriszfay]]

Backed out for causing multiple Gtest failures

Backout link

Push with failures

Failure log
Failure log 2

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/ae56f81180d4
https://hg.mozilla.org/integration/autoland/rev/e6475f35919b
Add telemetry for why DNS lookups miss the cache r=necko-reviewers,valentin,mxinden
https://github.com/mozilla-firefox/firefox/commit/981ed2cf4644
https://hg.mozilla.org/integration/autoland/rev/4503365575e7
Make the DNS negative-cache lifetime a pref and raise the default r=necko-reviewers,valentin
https://github.com/mozilla-firefox/firefox/commit/641d6a24313d
https://hg.mozilla.org/integration/autoland/rev/a5178f24fb6a
apply code formatting via Lando

Comment 7

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/e6475f35919b
https://hg.mozilla.org/mozilla-central/rev/4503365575e7
https://hg.mozilla.org/mozilla-central/rev/a5178f24fb6a