1973036 - Cache panel seems to be always empty

Status: RESOLVED FIXED

(DevTools :: Netmonitor, defect)

Description

[Alexandre Poirot [:ochameau]]

STR:

• open some page having cached request, example: bugzilla or phabricator
• select one of those requests and open the cache panel

The cache panel will be empty on all requests

Comment 1

[Pascal Chevrel (relman team) -> :pascalc]

Mopzregression:
Last good revision: 6aff7acd8390f8d83eb15589a0ceb376cedb2416 (2021-10-28)
First bad revision: c97b176528631e697dc1c1191b1f6b4dc1e0726a (2021-10-29)
Pushlog:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=6aff7acd8390f8d83eb15589a0ceb376cedb2416&tochange=c97b176528631e697dc1c1191b1f6b4dc1e0726a

Comment 2

[Alexandre Poirot [:ochameau]]

This comes from:
https://searchfox.org/mozilla-central/rev/beba5cde846f944c4d709e75cbe499d17af880a4/devtools/shared/network-observer/NetworkResponseListener.sys.mjs#476

if (this.#request.fromCache || responseStatus == 304) {

where this.#request is an nsIChannel, which, I think, never exposed such a fromCache boolean.

This precise check seems to have been wrong from day 1, from bug 859051.
But we might have regressed the other condition around responseStatus in bug 1815460.
The panel was most likely only functional thanks to the second condition.

For some reason, the existing test covering this patch triggers a 304 request from JS:
https://searchfox.org/mozilla-central/source/devtools/client/netmonitor/test/browser_net_cache_details.js
and the responseStatus is set to 304, whereas it is always set to 200 in all the websites I use as example.

Comment 3

[Julian Descottes [:jdescottes]]

https://searchfox.org/mozilla-central/rev/beba5cde846f944c4d709e75cbe499d17af880a4/remote/shared/NetworkResponse.sys.mjs#64-70

// For 304 responses, the response will be replaced by the cached response
// between responseStarted and responseCompleted, which will effectively
// change the status and statusMessage.
// Until the issue linked above has been discussed and closed, we will
// cache the status/statusMessage in order to ensure consistent values
// between responseStarted and responseCompleted.
this.#status = this.#isDataURL ? 200 : this.#channel.responseStatus;

We actually had an issue with this in BiDi, and we read the responseStatus early to avoid having it replaced with 200

Comment 4

[Julian Descottes [:jdescottes]]

And yes prior to Bug 1815460, we were reading the status from httpActivity, which was probably populated as early as possible:

  (this.#request.fromCache || this.#httpActivity.responseStatus == 304)

Comment 5

[Julian Descottes [:jdescottes]]

Attachment: Bug 1973036 - [devtools] Stop reading the responseStatus dynamically from the channel to fetch cache details

Comment 6

[Julian Descottes [:jdescottes]]

Attachment: Bug 1973036 - [devtools] Stop reading nsIChannel.fromCache which doesn't exist

Comment 7

[Alexandre Poirot [:ochameau]]

This is yet another reason why the cache panel is sometimes blank.
nsICacheStorage.asyncOpenURI would sometime never call DevTool's onCacheEntryCheck/onCacheEntryAvailable listeners.
I don't have precise STR, but reloading many times on wikipedia.org reproduces intermittently.

Comment 8

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/6d29415b899a
https://hg.mozilla.org/integration/autoland/rev/377035d03764
[devtools] Stop reading the responseStatus dynamically from the channel to fetch cache details r=devtools-reviewers,ochameau
https://github.com/mozilla-firefox/firefox/commit/30dbb48109d3
https://hg.mozilla.org/integration/autoland/rev/721a2609a1f0
[devtools] Stop reading nsIChannel.fromCache which doesn't exist r=devtools-reviewers,ochameau

Comment 9

[Atila Butkovits]

https://hg.mozilla.org/mozilla-central/rev/377035d03764
https://hg.mozilla.org/mozilla-central/rev/721a2609a1f0

Comment 10

[BugBot [:suhaib / :marco/ :calixte]]

The patch landed in nightly and beta is affected.
:jdescottes, is this bug important enough to require an uplift?

• If yes, please nominate the patch for beta approval.
  • See https://wiki.mozilla.org/Release_Management/Requesting_an_Uplift for documentation on how to request an uplift.
• If no, please set status-firefox141 to wontfix.

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