[HttpKernel] fix session tracking in surrogate master requests

[nicolas-grekas]

Q	A
Branch?	3.4
Bug fix?	yes
New feature?	no
BC breaks?	no
Deprecations?	no
Tests pass?	yes
Fixed tickets	-
License	MIT
Doc PR	-

Spotted while looking at ESI fragments resolved byHttpCache: right now when the master request starts the session, fragments are not cacheable anymore, even when they do not use the session.

[nicolas-grekas]

(failure will be fixed once merged up to master)

[nicolas-grekas]

ping @symfony/deciders votes pending, this "just" fixes ESI with HttpCache, which are broken (found in training sessions by @jpauli )

[stof]

Looks good to me

[stefandoorn]

@nicolas-grekas Maybe unrelated, maybe not, I just upgraded from 3.4.2 to 3.4.11 on a site that heavily uses ESI fragments, and performance degraded within a second. Had to revert the upgrade (didn't expect this - locally no issue) to make performance be 'normal' again. Unfortunately no benchmarks or proper debug information available - locally also Blackfire doesnt show me any real differences.

Might be related to this?

[nicolas-grekas]

Only a profile could tell...

[nicolas-grekas]

Maybe try branch 3.4-dev?

[stefandoorn]

Yeah, was afraid about that :-D Will see if I can get that :) And I'll try the dev branch, good one.

[stefandoorn]

I can confirm that on 3.4.2 files were being written to the http_cache folder inside the cache folder, but on 3.4.11 it's not happening. Tested locally.

[danrot]

@nicolas-grekas Are you aware that the session is always used in tests now? That's because of this $session->isEmpty statement. And I am relying on that in one of our tests. For now I had no better way to deactivate the session completely, which also doesn't feel very good...

Isn't that something that should be fixed in Symfony? I don't really see a nice way of handling this in our codebase (there are a few ways, but I would consider all of them dirty).

[nicolas-grekas]

@danrot I know about #27714

[nicolas-grekas]

@danrot can you please check #27714 and confirm it fixes the issue for you also?

[danrot]

Just tested it, it works 👍 Thanks a lot!