fix: only generate links when fields expand to href [DHIS2-21856] (2.43)#24501
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Single-object GET treated any field preset (e.g. :owner) as if href was requested, triggering deep link generation that reflectively initializes every lazy collection of the entity. On objects with very large collections (e.g. a user role with 240k members) this loads and L2-caches every member entity, taking 30+ seconds of CPU per request. Only *, :all and :simple actually expand to the transient href property, so only those (and a literal href field) now trigger link generation. Response payloads are unchanged for all field values. AI Assisted
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Fix: only generate links when fields expand to href
Problem
A production Glowroot trace showed
GET /api/userRoles/{id}?fields=:owner,access,displayName,authoritiestaking 33s wall / 31s CPU / 17.5 GB allocated.AbstractFullReadOnlyControllertreats any field preset (:owner,:identifiable, ...) as ifhrefwas requested. This triggersLinkService.generateLinks(..., deep=true), which reflectively invokes every IdentifiableObject getter on the entity - initializing every lazy collection. For a user role with ~241k members this loads all memberUserentities and pushes each one through the serializing L2 cache copier, then throws the result away (:ownernever serializeshref).Fix
Only
*,:alland:simplepresets actually expand to the transienthrefproperty, so only those (plus a literalhreffield, incl. nested likeusers[href]) now trigger link generation. Everything that previously returnedhrefstill returns it - response payloads are unchanged for all field values.Note: master got an equivalent (stricter) heuristic via #24011; this is a minimal standalone backport that additionally preserves the
:simpleand nested-href triggers.Verification
New parameterized tests in
AbstractCrudControllerTestasserthrefpresence for:all,*,:simple,href,id,href,id,name,hrefand absence for:owner,:identifiable,:nameable,:persisted,id,name(13/13 pass, H2).AI Assisted