Task 2 Implementation Report

Date: 2026-09-03 Task: Build the Lock-Free Snapshot Coordinator Worktree: D:/workSpace/PROJECT_SPACE/FT546/FT546MWS/worktrees/shadow-from-main-20260811

What Changed

Implemented the JVM-local, observation-only snapshot coordinator using one immutable AtomicReference<State> and compare-and-set transitions.

Added immutable PublishedShadowSnapshot metadata with generation, warehouse, synchronization time, and source signature.
Added ShadowSkipReason values for startup, busy, stale, warehouse, and concurrent outcomes.
Added ShadowSnapshotCoordinator with startup, ready, busy, and unavailable phases; bounded freshness checks; warehouse normalization through WarehouseIdNormalizer.equivalent; single observation leasing; refresh tickets; stamped publication; failure recovery state; and separately idempotent Legacy activity and observation-lease cleanup.
Added behavior tests for startup, one lease, busy admission, exact-once cleanup, concurrent publication invalidation, comparability invalidation, stale snapshots, warehouse mismatch, numeric warehouse equivalence, and failed-refresh recovery.
No gateway, SQL, cross-instance, or later-task behavior was added.

Files Changed

ruoyi-admin/src/main/java/com/ruoyi/algorithm/shadow/PublishedShadowSnapshot.java
ruoyi-admin/src/main/java/com/ruoyi/algorithm/shadow/ShadowSkipReason.java
ruoyi-admin/src/main/java/com/ruoyi/algorithm/shadow/ShadowSnapshotCoordinator.java
ruoyi-admin/src/test/java/com/ruoyi/algorithm/shadow/ShadowSnapshotCoordinatorTest.java

TDD Evidence

RED

The initial direct reactor command could not resolve locally built reactor dependencies:

D:/BDevTools/maven/apache-maven-3.9.11/bin/mvn.cmd -pl ruoyi-admin -Dtest=ShadowSnapshotCoordinatorTest test

It failed before compilation with missing ruoyi-framework, ruoyi-quartz, ruoyi-generator, and fortucky-algorithm artifacts. Following the brief, the same named test scope was rerun with the reactor fallback:

D:/BDevTools/maven/apache-maven-3.9.11/bin/mvn.cmd -pl ruoyi-admin -am -Dtest=ShadowSnapshotCoordinatorTest -Dsurefire.failIfNoSpecifiedTests=false test

Expected RED output:

[ERROR] ...ShadowSnapshotCoordinatorTest.java:[108,13] cannot find symbol
  symbol:   class ShadowSnapshotCoordinator
[ERROR] ...ShadowSnapshotCoordinatorTest.java:[112,20] cannot find symbol
  symbol:   class PublishedShadowSnapshot
[ERROR] ...ShadowSnapshotCoordinatorTest.java:[116,33] cannot find symbol
  symbol:   class ShadowSnapshotCoordinator
[ERROR] ...ShadowSnapshotCoordinatorTest.java:[116,72] cannot find symbol
  symbol:   class PublishedShadowSnapshot
[INFO] ruoyi-admin ........................................ FAILURE
[INFO] BUILD FAILURE

The failure was the intended missing-production-type compilation failure; no test behavior ran before implementation.

GREEN

After the minimum production implementation, the focused command was run twice:

D:/BDevTools/maven/apache-maven-3.9.11/bin/mvn.cmd -pl ruoyi-admin -am -Dtest=ShadowSnapshotCoordinatorTest -Dsurefire.failIfNoSpecifiedTests=false test

Run 1:

[INFO] Tests run: 5, Failures: 0, Errors: 0, Skipped: 0
[INFO] ruoyi-admin ........................................ SUCCESS
[INFO] BUILD SUCCESS

Run 2:

[INFO] Tests run: 5, Failures: 0, Errors: 0, Skipped: 0
[INFO] ruoyi-admin ........................................ SUCCESS
[INFO] BUILD SUCCESS

Both runs completed without timing sleeps.

Full-Suite Evidence

Before committing, the relevant reactor suite was run once:

D:/BDevTools/maven/apache-maven-3.9.11/bin/mvn.cmd -pl ruoyi-admin -am -Dsurefire.failIfNoSpecifiedTests=false test

Result:

fortucky-algorithm: Tests run: 122, Failures: 0, Errors: 0, Skipped: 0
ruoyi-admin:        Tests run:  26, Failures: 0, Errors: 0, Skipped: 0
[INFO] BUILD SUCCESS

Total: 148 tests, 0 failures, 0 errors, 0 skipped. The output included existing Lombok equals/hashCode and deprecation warnings in unrelated sources; none were introduced by this task.

Self-Review

Confirmed the staged change contained exactly the four brief-listed implementation/test files.
git diff --cached --check completed cleanly.
Confirmed the coordinator has one AtomicReference<State> and CAS loops for admission, exit, lease cleanup, refresh begin, publication, and refresh failure.
Confirmed exit and finishObservation use separate per-admission AtomicBoolean guards.
Confirmed caller admission performs only bounded in-memory work and atomic transitions; there is no synchronized block, lock, wait, sleep, database call, gateway call, or SQL behavior.
Confirmed the publication CAS uses the refresh ticket's full stamped State object, so activity or any intervening state replacement invalidates publication even when generation values match.
Confirmed numeric warehouse equivalence delegates to the Task 1 normalizer and freshness defaults to 60 seconds.
No subagents or external reviewers were dispatched, per request.

Commit

c6a8b4f feat: coordinate stable shadow snapshots

Concerns

The coordinator intentionally does not wait for the configured quiet interval; it records quietSince, while the later background worker owns waiting and refresh scheduling.
Gateway integration, SQL refresh/publication, metrics, and cross-instance coordination remain later tasks by design.
The report is a standalone delivery artifact at the requested path; the feature commit contains the four files listed in the brief.

Fix Round 1

Changed ShadowSnapshotCoordinator to accept an injectable java.time.Clock; exit now records clock.instant() instead of Instant.now().
Added tests proving stale/warehouse skips transition to BUSY and recover via refresh, plus deterministic quiet-since timing.
RED: focused reactor command initially failed in this shell because mvn resolved an incompatible Maven/plugin environment; the corrected Maven 3.9.11 command then compiled and exercised the new tests.
GREEN: D:/BDevTools/maven/apache-maven-3.9.11/bin/mvn.cmd -pl ruoyi-admin -am -Dtest=ShadowSnapshotCoordinatorTest '-Dsurefire.failIfNoSpecifiedTests=false' test passed twice; 7 tests, 0 failures, 0 errors each run.
Commit: pending.
Concerns: default constructors retain Clock.systemUTC() behavior; no gateway, SQL, or Legacy behavior changed.

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