Cache resolved data in Manage Old Data page

[subwaycookiecrunch]

Fixes #16843 (JENKINS-76278)

manage.jelly calls it.data three times — once to scan flags, once for the version table, once for the unreadable data table. getData() iterates every entry and resolves each RunSaveableReference through Run.fromExternalizableId(), which does a job lookup + build-by-number lookup. With 30k+ entries that's roughly 90k lookups for a single page load, enough to peg the CPU for 40+ minutes.

Stashed the result in a Jelly variable so resolution happens once. Also capped the table at 1000 rows since rendering 30k <tr> elements locks up the browser regardless of backend speed. The cap is display-only — upgrade and discard still work on the full data set.

Testing done

Added managePageRendering() to OldDataMonitorTest — registers old data on a build, confirms it shows up in getData(), then loads the manage page via WebClient and verifies it renders without error.

Existing tests (memory, slowDiscard, unlocatableRun) continue to pass since the Java side is unchanged.

Screenshots (UI changes only)

N/A, no visual design changes, just a display cap with a warning message when entry count exceeds 1000.

Before

After

Proposed changelog entries

• Cache resolved data on the Manage Old Data page to avoid repeated expensive lookups with large entry counts

Proposed changelog category

/label bug

Proposed upgrade guidelines

N/A

Submitter checklist

• The issue, if it exists, is well-described.
• The changelog entries and upgrade guidelines are appropriate for the audience affected by the change (users or developers, depending on the change) and are in the imperative mood (see examples). Fill in the Proposed upgrade guidelines section only if there are breaking changes or changes that may require extra steps from users during upgrade.
• There is automated testing or an explanation as to why this change has no tests.
• New public classes, fields, and methods are annotated with @Restricted or have @since TODO Javadocs, as appropriate.
• New deprecations are annotated with @Deprecated(since = "TODO") or @Deprecated(forRemoval = true, since = "TODO"), if applicable.
• UI changes do not introduce regressions when enforcing the current default rules of Content Security Policy Plugin. In particular, new or substantially changed JavaScript is not defined inline and does not call eval to ease future introduction of Content Security Policy (CSP) directives (see documentation).
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Desired reviewers

@basil @MarkEWaite

[andreahlert]

LGTM

[andreahlert]

@subwaycookiecrunch The description says "Fixes #16843" but the title references JENKINS-76278. Which issue does this actually fix? Please align the "Fixes" line with the correct issue.

[timja]

why do you need to encode this? you use a > elsewhere on the page?

Suggested change

	<j:if test="${item.value.extra!=null and item.value=='' and count &lt; maxDisplay}">
	<j:if test="${item.value.extra!=null and item.value=='' and count < maxDisplay}">

[andreahlert]

@timja, I think it might be because in XML, inside an attribute value, < is usually escaped as < so the parser doesn’t treat it as the start of a tag, while > typically doesn’t need escaping. So the < here might be intentional, and using > elsewhere on the page doesn’t necessarily contradict that. I could be wrong; if in Jelly it’s safe to use a raw < in the attribute, then simplifying makes sense.

[timja]

I'd try it and if it doesn't work its fine but better to try first

[subwaycookiecrunch]

@timja @andreahlert right, raw < does break the XML parser in attribute values so that won't work. I just flipped the comparison to maxDisplay > count instead , no entity needed and it's consistent with how I already wrote the check on line 52. Pushed.

[subwaycookiecrunch]

@andreahlert yeah sorry about that, #16843 is the GitHub mirror of JENKINS-76278 , they're the same issue. I'll clean up the description so it's not confusing. Thanks for catching it.