[claude] Keep the fwdata LcmCache alive during long syncs

[myieye]

[Claude, autonomous]

The LcmCache's 30-minute sliding expiration only resets when a new FwDataMiniLcmApi first touches the memory cache, so a sync that outlives it (large project, or paused in a debugger) gets its cache disposed mid-run. FwDataFactory.PreventEviction returns a disposable timer that touches the cache entry every 5 minutes; the sync service holds one for the duration of a sync. TryGetValue never creates or reloads, so a project explicitly closed for FieldWorks stays closed.

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📝 Walkthrough

Walkthrough

Changes

Synchronization Cache Guard

Layer / File(s)	Summary
Add cache keepalive helper backend/FwLite/FwDataMiniLcmBridge/FwDataFactory.cs	Adds PreventEviction, which periodically accesses a project's cached LcmCache entry and returns a disposable timer guard.
Integrate eviction guard into sync backend/FwLite/FwLiteProjectSync/CrdtFwdataProjectSyncService.cs, backend/Testing/FwHeadless/Services/SyncWorkerTestHarness.cs	Injects FwDataFactory, applies the guard during synchronization, and updates the test harness constructor arguments.

Estimated code review effort: 2 (Simple) | ~10 minutes

Poem

I’m a rabbit guarding cache,
Tapping keys through every dash.
Sync runs long, the timer sings,
No eviction clips its wings.
Hop, hop—dispose when done!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: keeping LcmCache alive during long syncs.
Description check	✅ Passed	The description directly explains the keep-alive timer and its use during syncs.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 1

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

backend/Testing/FwHeadless/Services/SyncWorkerTestHarness.cs (1)

251-256: 📐 Maintainability & Code Quality | 🟠 Major | 🏗️ Heavy lift

Add integration coverage for the keepalive path.

This harness mocks CrdtFwdataProjectSyncService and supplies null! for FwDataFactory, so the new PreventEviction call is never exercised. Add a targeted integration or round-trip test using the real sync service and a real FwData project, or a focused test that verifies the keepalive is created and disposed.

As per coding guidelines, backend/FwLite/FwLiteProjectSync/**/*.cs synchronization changes must be covered with integration or round-trip tests.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@backend/Testing/FwHeadless/Services/SyncWorkerTestHarness.cs` around lines
251 - 256, Extend the sync worker test coverage around the
CrdtFwdataProjectSyncService setup to exercise the keepalive path introduced by
PreventEviction. Prefer a targeted integration or round-trip test using a real
sync service and FwData project; otherwise verify that the keepalive is created
and disposed, rather than relying on the existing Strict mock with null
FwDataFactory.

Source: Coding guidelines

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@backend/FwLite/FwDataMiniLcmBridge/FwDataFactory.cs`:
- Around line 138-143: Update PreventEviction to touch the cache entry
immediately by invoking cache.TryGetValue with the computed key before creating
and returning the periodic Timer. Keep the existing 5-minute refresh interval
and callback behavior unchanged.

---

Outside diff comments:
In `@backend/Testing/FwHeadless/Services/SyncWorkerTestHarness.cs`:
- Around line 251-256: Extend the sync worker test coverage around the
CrdtFwdataProjectSyncService setup to exercise the keepalive path introduced by
PreventEviction. Prefer a targeted integration or round-trip test using a real
sync service and FwData project; otherwise verify that the keepalive is created
and disposed, rather than relying on the existing Strict mock with null
FwDataFactory.

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📥 Commits

Reviewing files that changed from the base of the PR and between bb3f331 and db77397.

📒 Files selected for processing (3)

• backend/FwLite/FwDataMiniLcmBridge/FwDataFactory.cs
• backend/FwLite/FwLiteProjectSync/CrdtFwdataProjectSyncService.cs
• backend/Testing/FwHeadless/Services/SyncWorkerTestHarness.cs

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Build	Status	Details	Updated (UTC)
default (Inspect)	✅ No changes detected	-	Jul 30, 2026, 10:57 AM
e2e (Inspect)	✅ No changes detected	-	Jul 30, 2026, 11:04 AM

[myieye]

@hahn-kev Regarding the discussion about moving the PreventEviction higher up in the call stack: I agree that everything up there should easily happen fast enough for it to not be relevant. So, I left it where it is. It went through a few tiny refactors since you approved, but it's essentially still the same thing.