XCOMMONS-3258: Introduce a cache for ServletEnvironment#getResource

[michitux]

Jira URL

https://jira.xwiki.org/browse/XCOMMONS-3258

Changes

Description

• Introduce a dynamically initialized cache to avoid issues with recursive component initialization calls.
• Add test cases to confirm that the cache works as expected and that cache initialization can do recursive calls for getting resources.

Clarifications

• As the proposal at https://forum.xwiki.org/t/cache-servletcontext-getresource/16416 and the discussion yesterday didn't bring a real conclusion about introducing a "development" mode, the cache can currently be disabled with the regular CacheControl mechanism that we're already using for other caches. In my opinion, we should discuss improving the cache control mechanism to limit it to users with programming right as this seems to be the easiest solution without introducing any side effects.
• Without the dynamic initialization, an endless recursion happens because the cache manager loads the configuration from the servlet environment, calling getResource.

Screenshots & Video

No UI changes.

Executed Tests

• bin/dumbbench --float -p 0.1 -i 100 -- wget -q -o NUL -O NUL --load-cookies cookies.txt "http://127.0.0.1:1700/xwiki/bin/view/NoSpace/NoPage" - the performance seems to be back to what it was approximately in 15.10.16, 103ms vs. 104ms in 15.10.16.
• LANG=C.UTF-8 mvn clean install -Pdocker,legacy,integration-tests,snapshotModules,quality,distribution,flavor-integration-tests,standalone in xwiki-commons.

Expected merging strategy

• Prefers squash: Yes
• Backport on branches:
  • stable-16.10.x (as this fixes an important performance regression)

[github-actions]

The backport to stable-16.10.x failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-stable-16.10.x stable-16.10.x
# Navigate to the new working tree
cd .worktrees/backport-stable-16.10.x
# Create a new branch
git switch --create backport-1234-to-stable-16.10.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 51f405d602712ef32248cfb98b982efd3c4a9e43
# Push it to GitHub
git push --set-upstream origin backport-1234-to-stable-16.10.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-stable-16.10.x

Then, create a pull request where the base branch is stable-16.10.x and the compare/head branch is backport-1234-to-stable-16.10.x.