[dvc][cc] Fix unsafe DVRT CDC version swap by kvargha · Pull Request #2795 · linkedin/venice

kvargha · 2026-05-13T23:09:35Z

Problem Statement

This is the DVRT-based CDC counterpart to #2280, which added the same version-swap-by-control-message handling to the legacy VeniceChangelogConsumerImpl. Both PRs sit on top of #2245, which introduced the multi-region VSM broadcast on the controller/server side.

The current version-swap behavior in VeniceChangelogConsumerDaVinciRecordTransformerImpl is unsafe in three ways:

Acts on VSMs meant for another region. Under A/A, the same logical swap is broadcast per source region. A consumer in region X should only act on VSMs originating from region X (sourceRegion), but today's per-partition flip ignores sourceRegion and acts on the first VSM it sees.
Acts on stale VSMs from a previous version. Re-pushes replay previous VTs' version swap messages into the new VT. Without filtering by generationId and oldServingVersionTopic, the consumer can be misled into a swap by a stale message left over from an earlier push (or by historical VSMs replayed after restarting from EARLIEST, or after a rollback to a lower version).
No protection against the future version's ingestion outpacing the current version's. The current-version transformer is throttled by the user's post-poll processing (records have to be drained through poll() before more are ingested), but the future-version transformer's ingestion bypasses user post-poll entirely. Whenever post-poll is slow — or under A/A where DCs ingest at different rates across versions — the future version's transformer can consume past the swap point before the current version has reached it. Records that should have surfaced on the current side are then silently swallowed by the future side: data loss at swap time.

Solution

Introduce RecordTransformerVersionSwapCoordinator and route the DVRT CDC consumer's onVersionSwap through it when versionSwapByControlMessageEnabled = true. The coordinator addresses the three issues above:

Region filter. isRelevant() drops VSMs whose sourceRegion is not this client's region.
Generation / old-VT filter. isRelevant() drops VSMs with generationId == -1, VSMs targeting a version not greater than the highest already promoted to serving (defends against rollback + replay-from-EARLIEST), and — once a swap is armed — VSMs whose generationId or oldServingVersionTopic / newServingVersionTopic don't match the in-progress swap.
Future-side pause. Once a partition has observed VSMs from every destinationRegion on the future side, the coordinator pauses Kafka prefetch on that partition until the cross-partition barrier closes. The cutover atomically flips partitionToVersionToServe and resumes the paused partitions; a watchdog force-commits if the barrier doesn't close within versionSwapTimeoutInMs (default 30 min), bounding the vulnerable window.

Backward compatible: legacy per-partition flip is preserved when the config is false (the default).

Trade-off (documented in the coordinator's class javadoc): Kafka's consumer.pause() doesn't truncate the in-flight batch, so records past the VSM in the same batch flow through processPut on both sides — surfaced on current, silently dropped on future. The design accepts this assuming approximate poll-batch alignment between current and future leaders; the watchdog bounds the window.

Code changes

Gated behind existing config versionSwapByControlMessageEnabled (default false). Watchdog uses existing versionSwapTimeoutInMs (default 30 min). No new configs.
New log lines (bounded by partitions × regions per swap; rate-limit not needed).

Concurrency-Specific Checks

No races: all state-mutating coordinator methods are synchronized on the instance.
Cutover (flip + resume) runs under the coordinator's monitor.
No blocking calls in the critical section; watchdog runs on a daemon executor.
Region accumulators are only touched under the coordinator's monitor.
Watchdog/commit exceptions are captured and surfaced via poll(), not silently dropped.

How was this PR tested?

Unit tests added: RecordTransformerVersionSwapCoordinatorTest (18), VeniceChangelogConsumerDaVinciRecordTransformerAaVersionSwapTest (7).
Integration tests added: TestAaVersionSwapRecordTransformer (6 e2e scenarios — pre/post-swap, mid-swap restart, watchdog timeout, back-to-back swaps, rollback, buffer pressure).
Extended existing tests for the new onVersionSwap() signature.
Backward compat verified: flag default false keeps legacy behavior.

Does this PR introduce any user-facing or breaking changes?

No — gated behind versionSwapByControlMessageEnabled (default false).

Introduce RecordTransformerVersionSwapCoordinator, a barrier that gates version swap until every assigned partition observes VSMs from every region on both current and future version topics. Replaces the legacy per-partition immediate flip, which is incorrect under AA topology because sibling regions may not have replicated their VSMs yet. - Coordinator: state machine IDLE -> IN_PROGRESS -> {COMMITTED,TIMED_OUT,FAILED}; atomic cutover across all assigned partitions on barrier completion. - Pauses Kafka prefetch on future-side partitions until commit via new pause/resume hooks on InternalDaVinciRecordTransformer + StoreIngestionTask. - Watchdog timeout force-commits if the barrier does not close in time. - Legacy per-partition path preserved when versionSwapByControlMessageEnabled is false. Tests: 18 coordinator unit tests, 7 CDC consumer AA tests, and 6 end-to-end TestAaVersionSwapRecordTransformer scenarios. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Copilot

Pull request overview

This PR introduces a new RecordTransformerVersionSwapCoordinator that gates the DVRT-based CDC consumer's version-swap cutover until every assigned partition has observed VSMs from every region on both the current and future version topics, then atomically flips partitionToVersionToServe for all partitions in one synchronized block. The coordinator is gated behind the existing versionSwapByControlMessageEnabled flag (default false), so legacy per-partition flip behavior is preserved.

Changes:

New RecordTransformerVersionSwapCoordinator (state machine: IDLE → IN_PROGRESS → {COMMITTED, TIMED_OUT, FAILED}) plumbed into VeniceChangelogConsumerDaVinciRecordTransformerImpl.
InternalDaVinciRecordTransformer gains pause/resume Kafka-prefetch hooks (wired by StoreIngestionTask) and onVersionSwap now takes the VersionSwap payload.
New unit + integration tests covering AA cutover, timeout watchdog, rollback, restart, back-to-back swaps, and buffer pressure.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 14 comments.

Show a summary per file

File	Description
`clients/da-vinci-client/.../RecordTransformerVersionSwapCoordinator.java`	New cross-region barrier coordinator with state machine, watchdog, and per-side accumulators
`clients/da-vinci-client/.../VeniceChangelogConsumerDaVinciRecordTransformerImpl.java`	Wires the coordinator, surfaces watchdog failures via `poll()`, branches between AA and legacy paths in `onVersionSwap`
`clients/da-vinci-client/.../InternalDaVinciRecordTransformer.java`	New pause/resume handlers and `onVersionSwap(VersionSwap, …)` signature; back-reference initialization
`clients/da-vinci-client/.../StoreIngestionTask.java`	Wires pause/resume handlers from the SIT into the transformer; passes `VersionSwap` payload
`clients/da-vinci-client/test/.../RecordTransformerVersionSwapCoordinatorTest.java`	18 unit tests for the coordinator's relevance/accumulation/state-machine behaviour
`clients/da-vinci-client/test/.../VeniceChangelogConsumerDaVinciRecordTransformerAaVersionSwapTest.java`	7 unit tests covering pause/resume, foreign-region/legacy/stale filtering, atomic flip, failure surfacing
`clients/da-vinci-client/test/.../VeniceChangelogConsumerDaVinciRecordTransformerImplTest.java`	Updates legacy `onVersionSwap` call sites to the new 4-arg signature
`clients/da-vinci-client/test/.../RecordTransformerTest.java`	Updates `onVersionSwap` call site and adds pause/resume wiring test
`internal/venice-test-common/.../TestAaVersionSwapRecordTransformer.java`	New end-to-end integration tests: pre/post swap, restart, watchdog timeout, back-to-back swaps, rollback, buffer pressure

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+        }
+      } catch (Exception exception) {
+        versionSwapCoordinator.failSwap(exception);
+        throw exception;


+  public synchronized boolean isRelevant(VersionSwap vsm, boolean isCurrentSide, int transformerVersion) {
+    if (vsm == null || vsm.getGenerationId() == -1) {
+      return false;
+    }
+    if (vsm.getSourceRegion() == null || !clientRegionName.equals(vsm.getSourceRegion().toString())) {
+      return false;
+    }
+    String oldTopic = vsm.getOldServingVersionTopic().toString();
+    String newTopic = vsm.getNewServingVersionTopic().toString();
+    if (!Version.isVersionTopic(newTopic)) {
+      return false;
+    }
+    String transformerTopic = Version.composeKafkaTopic(storeName, transformerVersion);
+    if (isCurrentSide) {
+      if (!transformerTopic.equals(oldTopic)) {
+        return false;
+      }
+    } else {
+      if (!transformerTopic.equals(newTopic)) {
+        return false;
+      }
+    }
+    int newVersion = Version.parseVersionFromVersionTopicName(newTopic);
+    if (newVersion <= computeMaxServedVersion()) {
+      return false;
+    }
+    if (state.get() == State.IN_PROGRESS) {
+      if (vsm.getGenerationId() != activeGenerationId) {
+        return false;
+      }
+      if (!oldTopic.equals(activeOldVersionTopic) || !newTopic.equals(activeNewVersionTopic)) {
+        return false;
+      }
+    }
+    return true;
+  }


+  public synchronized void commitSwap() {
+    if (!state.compareAndSet(State.IN_PROGRESS, State.COMMITTED)) {
+      return;
+    }
+    cancelWatchdog();
+    try {
+      flipServingVersion();
+      resumeFutureSide();
+    } catch (Exception flipFailure) {
+      handleTerminalFailure(flipFailure);
+      throw flipFailure;
+    }
+    if (changeCaptureStats != null) {
+      changeCaptureStats.emitVersionSwapCountMetrics(SUCCESS);
+    }
+    LOGGER.info(
+        "Version swap committed for store: {}, swap: {} -> {}, partitions: {}",
+        storeName,
+        activeOldVersionTopic,
+        activeNewVersionTopic,
+        assignedPartitionsSnapshot);
+    clearSwapState();
+  }
+
+  /**
+   * Forces the cutover after the configured timeout has elapsed without all VSMs being observed.
+   * Counts as a recoverable success — emits a single SUCCESS metric and a WARN log; no separate
+   * timeout counter exists by design.
+   */
+  public synchronized void timeoutSwap() {
+    if (!state.compareAndSet(State.IN_PROGRESS, State.TIMED_OUT)) {
+      return;
+    }
+    cancelWatchdog();
+    try {
+      flipServingVersion();
+      resumeFutureSide();
+    } catch (Exception flipFailure) {
+      handleTerminalFailure(flipFailure);
+      return;
+    }
+    if (changeCaptureStats != null) {
+      changeCaptureStats.emitVersionSwapCountMetrics(SUCCESS);
+    }
+    LOGGER.warn(
+        "Version swap timed out (forced cutover) for store: {}, swap: {} -> {}, partitions: {}",
+        storeName,
+        activeOldVersionTopic,
+        activeNewVersionTopic,
+        assignedPartitionsSnapshot);
+    clearSwapState();
+  }


+  private void flipServingVersion() {
+    for (int partition: assignedPartitionsSnapshot) {
+      partitionToVersionToServe.put(partition, activeNewVersion);
+    }


+  private int computeMaxServedVersion() {
+    int max = -1;
+    for (int version: partitionToVersionToServe.values()) {
+      if (version > max) {
+        max = version;
+      }
+    }
+    return max;
+  }


+  private static void drainForDuration(
+      PollFunction pollFn,
+      Map<String, ChangeEvent<GenericRecord>> seen,
+      List<String> orderedKeys,
+      long drainSeconds) {
+    long deadline = System.currentTimeMillis() + drainSeconds * 1000;
+    while (System.currentTimeMillis() < deadline) {
+      drain(pollFn, seen, orderedKeys);
+    }
+  }


+  private static void pollUntilRangeObserved(
+      PollFunction pollFn,
+      Map<String, ChangeEvent<GenericRecord>> seen,
+      List<String> orderedKeys,
+      int startInclusive,
+      int endExclusive) {
+    TestUtils.waitForNonDeterministicAssertion(POLL_TIMEOUT_SECONDS, TimeUnit.SECONDS, true, () -> {
+      drain(pollFn, seen, orderedKeys);
+      for (int i = startInclusive; i < endExclusive; i++) {
+        assertNotNull(seen.get(String.valueOf(i)), "Key " + i + " not yet observed");
+      }
+    });
+  }


+    this.timeoutExecutor = Executors.newSingleThreadScheduledExecutor(
+        new DaemonThreadFactory("RecordTransformerVersionSwapCoordinator-" + storeName));


+  /** Convenience overload — produces records to dc-0's RT, which is where consumers subscribe. */
+  private void writeRecords(String storeName, int startIndex, int endIndexExclusive) {
+    try (VeniceSystemProducer producer = IntegrationTestPushUtils.getSamzaProducer(
+        childDatacenters.get(0).getClusters().get(CLUSTER_NAMES[0]),
+        storeName,
+        Version.PushType.STREAM)) {
+      producer.start();
+      for (int i = startIndex; i < endIndexExclusive; i++) {
+        TestChangelogKey key = new TestChangelogKey();
+        key.id = i;
+        TestChangelogValue value = new TestChangelogValue();
+        value.firstName = "first_" + i;
+        value.lastName = "last_" + i;
+        sendStreamingRecord(producer, storeName, key, value, null);
+      }


+  private void flipServingVersion() {
+    for (int partition: assignedPartitionsSnapshot) {
+      partitionToVersionToServe.put(partition, activeNewVersion);
+    }
+  }


worktree-dvrt-cdc-aa-version-swap

@VisibleForTesting

Fixes 2 SpotBugs failures in the AA version-swap tests: - DP_DO_INSIDE_DO_PRIVILEGED (5x Field.setAccessible calls in the unit test's setUp + 3 test methods): replaced with @VisibleForTesting getters/setters on VeniceChangelogConsumerDaVinciRecordTransformerImpl. Drops `final` from changeCaptureStats and versionSwapCoordinator so tests can swap them in. Matches the @VisibleForTesting idiom already used 8x in the same production class. - DE_MIGHT_IGNORE (TestAaVersionSwapRecordTransformer.deleteStoreQuietly silently swallowed Exception): now logs at debug level. Verified locally: spotbugsTest + spotbugsIntegrationTest both pass; all 8 tests in VeniceChangelogConsumerDaVinciRecordTransformerAaVersionSwapTest still pass. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Copilot

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 15 comments.

+      Exception versionSwapException = versionSwapThreadException.get();
+      if (versionSwapException != null) {
+        throw new VeniceException(
+            "Version Swap failed for store: " + storeName + " due to exception:",
+            versionSwapException);
+      }


+  public synchronized void commitSwap() {
+    if (!state.compareAndSet(State.IN_PROGRESS, State.COMMITTED)) {
+      return;
+    }
+    cancelWatchdog();
+    try {
+      flipServingVersion();
+      resumeFutureSide();
+    } catch (Exception flipFailure) {
+      handleTerminalFailure(flipFailure);
+      throw flipFailure;
+    }
+    if (changeCaptureStats != null) {
+      changeCaptureStats.emitVersionSwapCountMetrics(SUCCESS);
+    }
+    LOGGER.info(
+        "Version swap committed for store: {}, swap: {} -> {}, partitions: {}",
+        storeName,
+        activeOldVersionTopic,
+        activeNewVersionTopic,
+        assignedPartitionsSnapshot);
+    clearSwapState();
+  }


+    futureVersionRegionsConsumed.clear();
+    pausedCurrentPartitions.clear();
+    pausedFuturePartitions.clear();
+    assignedPartitionsSnapshot.clear();


+    String oldTopic = vsm.getOldServingVersionTopic().toString();
+    String newTopic = vsm.getNewServingVersionTopic().toString();
+    if (!Version.isVersionTopic(newTopic)) {
+      return false;
+    }
+    String transformerTopic = Version.composeKafkaTopic(storeName, transformerVersion);
+    if (isCurrentSide) {
+      if (!transformerTopic.equals(oldTopic)) {
+        return false;
+      }
+    } else {
+      if (!transformerTopic.equals(newTopic)) {
+        return false;
+      }
+    }
+    int newVersion = Version.parseVersionFromVersionTopicName(newTopic);


+  private void armIfNeeded(VersionSwap vsm) {
+    State current = state.get();
+    if (current == State.IN_PROGRESS) {
+      return;
+    }
+    activeGenerationId = vsm.getGenerationId();
+    activeOldVersionTopic = vsm.getOldServingVersionTopic().toString();
+    activeNewVersionTopic = vsm.getNewServingVersionTopic().toString();
+    activeNewVersion = Version.parseVersionFromVersionTopicName(activeNewVersionTopic);
+    currentVersionRegionsConsumed.clear();
+    futureVersionRegionsConsumed.clear();
+    pausedCurrentPartitions.clear();
+    pausedFuturePartitions.clear();
+    assignedPartitionsSnapshot.clear();
+    assignedPartitionsSnapshot.addAll(subscribedPartitions);
+    state.set(State.IN_PROGRESS);
+    scheduleTimeoutWatchdog();
+  }


+  private void deleteStoreQuietly(String storeName) {
+    CompletableFuture.runAsync(() -> {
+      try {
+        parentControllerClient.disableAndDeleteStore(storeName);
+      } catch (Exception e) {
+        LOGGER.debug("Best-effort cleanup of store {} failed", storeName, e);
+      }
+    });
+  }


+    java.util.List<Integer> paused = new java.util.ArrayList<>();
+    java.util.List<Integer> resumed = new java.util.ArrayList<>();
+    internalRecordTransformer.setPartitionPauseHandlers(paused::add, resumed::add);
+
+    internalRecordTransformer.pausePartitionConsumption(3);
+    internalRecordTransformer.pausePartitionConsumption(7);
+    internalRecordTransformer.resumePartitionConsumption(3);
+
+    assertEquals(paused, java.util.Arrays.asList(3, 7));
+    assertEquals(resumed, java.util.Collections.singletonList(3));


+    org.mockito.Mockito.when(schemaReader.getKeySchema()).thenReturn(keySchema);
+    org.mockito.Mockito.when(schemaReader.getValueSchema(1)).thenReturn(valueSchema);
+
+    changelogClientConfig = new ChangelogClientConfig<>().setD2ControllerClient(mock(D2ControllerClient.class))
+        .setSchemaReader(schemaReader)
+        .setStoreName(STORE)
+        .setControllerD2ServiceName(D2_SERVICE_NAME)
+        .setD2ServiceName(DEFAULT_CLUSTER_DISCOVERY_D2_SERVICE_NAME)
+        .setConsumerProperties(new Properties())
+        .setLocalD2ZkHosts("test_zookeeper")
+        .setD2Client(mock(D2Client.class))
+        .setVersionSwapByControlMessageEnabled(true)
+        .setClientRegionName(CLIENT_REGION)
+        .setTotalRegionCount(TOTAL_REGIONS);
+    changelogClientConfig.getInnerClientConfig()
+        .setMetricsRepository(getVeniceMetricsRepository(CHANGE_DATA_CAPTURE_CLIENT, CONSUMER_METRIC_ENTITIES, true));
+
+    VeniceChangelogConsumerClientFactory factory =
+        spy(new VeniceChangelogConsumerClientFactory(changelogClientConfig, null));
+    consumer = spy(new VeniceChangelogConsumerDaVinciRecordTransformerImpl<>(changelogClientConfig, factory));
+
+    // Spy stats so we can verify metric emissions
+    stats = spy(consumer.getChangeCaptureStats());
+    consumer.setChangeCaptureStats(stats);
+
+    // Coordinator was initialized with the original (pre-spy) stats reference; rebuild it so its
+    // metric emissions are routed through the spy.
+    consumer.setVersionSwapCoordinator(
+        new RecordTransformerVersionSwapCoordinator(
+            STORE,
+            CLIENT_REGION,
+            TOTAL_REGIONS,
+            changelogClientConfig.getVersionSwapTimeoutInMs(),
+            stats,
+            consumer.getPartitionToVersionToServe(),
+            consumer.getSubscribedPartitions(),
+            consumer.getVersionSwapThreadException()::set));
+
+    currentTransformer = consumer.new DaVinciRecordTransformerChangelogConsumer(STORE, CURRENT_VERSION, keySchema,
+        valueSchema, valueSchema, mock(com.linkedin.davinci.client.DaVinciRecordTransformerConfig.class));
+    futureTransformer = consumer.new DaVinciRecordTransformerChangelogConsumer(STORE, FUTURE_VERSION, keySchema,
+        valueSchema, valueSchema, mock(com.linkedin.davinci.client.DaVinciRecordTransformerConfig.class));
+
+    currentInternal =
+        (InternalDaVinciRecordTransformer<Integer, Integer, Integer>) mock(InternalDaVinciRecordTransformer.class);
+    futureInternal =
+        (InternalDaVinciRecordTransformer<Integer, Integer, Integer>) mock(InternalDaVinciRecordTransformer.class);


  /**
-   * Lifecycle event triggered when a version swap is detected for partitionId
-   * It is used for DVRT CDC.
+   * Lifecycle event triggered when a version swap is detected for partitionId.
+   * It is used for the DaVinciRecordTransformer CDC consumer. The {@code versionSwap} payload is
+   * required for AA-aware version-swap coordination (region filtering, generation-id matching);
+   * it may be null when invoked from legacy or test code paths.
   */
-  public void onVersionSwap(int currentVersion, int futureVersion, int partitionId) {
+  public void onVersionSwap(VersionSwap versionSwap, int currentVersion, int futureVersion, int partitionId) {
    if (isCDCRecordTransformer()) {
      ((VeniceChangelogConsumerDaVinciRecordTransformerImpl.DaVinciRecordTransformerChangelogConsumer) this.recordTransformer)
-          .onVersionSwap(currentVersion, futureVersion, partitionId);
+          .onVersionSwap(versionSwap, currentVersion, futureVersion, partitionId);
+    }
+  }


+  public synchronized void shutdown() {
+    cancelWatchdog();
+    timeoutExecutor.shutdownNow();
+  }
+


testAaVersionSwapRollback was asserting parent.currentVersion == 2 after rolling back from v3, but a bug in upstream PR linkedin#2785's VeniceParentHelixAdmin.updateParentVersionStatusAfterRollback double-decrements parent.currentVersion when 3+ versions exist: the admin-task handler decrements 3->2 (via VeniceHelixAdmin), then updateParentVersionStatusAfterRollback reads store.getCurrentVersion() (now 2), computes getBackupVersionNumber(versions, 2) = 1, and decrements again to 1. Child controllers decrement correctly to 2, so switch the assertion to getColoToCurrentVersions() which reflects each child's view. This will need to be tracked for upstream fix separately; the test sidesteps the parent-side double decrement. Verified locally: testAaVersionSwapRollback PASSED (222s). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

The class lands in the catch-all IntegrationTests_99 by default. With 7 tests totaling ~13 minutes, that shard overflows the 15-min CI limit (cancelled in PR linkedin#2795 CI). Assign it to its own shard so the runtime sits well within the per-shard budget. This is a manual entry pending the next run of scripts/ci/rebalance_test_shards.py with collected timing data. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Copilot

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 10 comments.

+  private void handleTerminalFailure(Exception error) {
+    if (changeCaptureStats != null) {
+      changeCaptureStats.emitVersionSwapCountMetrics(FAIL);
+    }
+    if (failureSurface != null) {
+      failureSurface.accept(error);
+    }
+    LOGGER.error(
+        "Version swap commit failed for store: {}, swap: {} -> {}",
+        storeName,
+        activeOldVersionTopic,
+        activeNewVersionTopic,
+        error);
+    clearSwapState();
+  }


+  private void flipServingVersion() {
+    for (int partition: assignedPartitionsSnapshot) {
+      partitionToVersionToServe.put(partition, activeNewVersion);
+    }


+      Exception versionSwapException = versionSwapThreadException.get();
+      if (versionSwapException != null) {
+        throw new VeniceException(
+            "Version Swap failed for store: " + storeName + " due to exception:",
+            versionSwapException);
+      }


+    }
+    if (vsm.getSourceRegion() == null || !clientRegionName.equals(vsm.getSourceRegion().toString())) {
+      return false;
+    }


+      try {
+        boolean isCurrentSide = currentVersion == getStoreVersion();
+        boolean isFutureSide = futureVersion == getStoreVersion();
+        if (!versionSwapCoordinator.isRelevant(versionSwap, isCurrentSide, getStoreVersion())) {
+          return;
+        }
+
+        if (isCurrentSide) {
+          if (versionSwapCoordinator.recordCurrentVsm(versionSwap, partitionId, internalRecordTransformer)) {
+            internalRecordTransformer.pausePartitionConsumption(partitionId);
+          }
+        } else if (isFutureSide) {
+          if (versionSwapCoordinator.recordFutureVsm(versionSwap, partitionId, internalRecordTransformer)) {
+            internalRecordTransformer.pausePartitionConsumption(partitionId);
+          }
+        }
+
+        if (versionSwapCoordinator.allPartitionsBothSidesComplete()) {
+          versionSwapCoordinator.commitSwap();
+        }
+      } catch (Exception exception) {
+        versionSwapCoordinator.failSwap(exception);
+        throw exception;
+      }


+  private void deleteStoreQuietly(String storeName) {
+    CompletableFuture.runAsync(() -> {
+      try {
+        parentControllerClient.disableAndDeleteStore(storeName);
+      } catch (Exception e) {
+        LOGGER.debug("Best-effort cleanup of store {} failed", storeName, e);
+      }
+    });
+  }


+  private static void drainForDuration(
+      PollFunction pollFn,
+      Map<String, ChangeEvent<GenericRecord>> seen,
+      List<String> orderedKeys,
+      long drainSeconds) {
+    long deadline = System.currentTimeMillis() + drainSeconds * 1000;
+    while (System.currentTimeMillis() < deadline) {
+      drain(pollFn, seen, orderedKeys);
+    }
+  }
+
+  /**
+   * Functional adapter so the same drain helpers work with both {@link VeniceChangelogConsumer}
+   * and {@link StatefulVeniceChangelogConsumer}, which don't share an interface.
+   */
+  @FunctionalInterface
+  private interface PollFunction {
+    @SuppressWarnings("rawtypes")
+    Collection<? extends PubSubMessage> poll(long timeoutMs);
+  }
+
+  @SuppressWarnings({ "rawtypes", "unchecked" })
+  private static void drain(
+      PollFunction pollFn,
+      Map<String, ChangeEvent<GenericRecord>> seen,
+      List<String> orderedKeys) {
+    Collection<? extends PubSubMessage> messages = pollFn.poll(500);
+    for (PubSubMessage message: messages) {
+      if (message.getKey() == null) {
+        continue; // skip control messages
+      }
+      String keyId;
+      Object key = message.getKey();
+      if (key instanceof GenericRecord) {
+        keyId = String.valueOf(((GenericRecord) key).get("id"));
+      } else if (key instanceof TestChangelogKey) {
+        keyId = String.valueOf(((TestChangelogKey) key).id);
+      } else {
+        keyId = String.valueOf(key);
+      }
+      seen.put(keyId, (ChangeEvent<GenericRecord>) message.getValue());
+      orderedKeys.add(keyId);
+    }
+  }


+    java.util.List<Integer> paused = new java.util.ArrayList<>();
+    java.util.List<Integer> resumed = new java.util.ArrayList<>();
+    internalRecordTransformer.setPartitionPauseHandlers(paused::add, resumed::add);
+
+    internalRecordTransformer.pausePartitionConsumption(3);
+    internalRecordTransformer.pausePartitionConsumption(7);
+    internalRecordTransformer.resumePartitionConsumption(3);
+
+    assertEquals(paused, java.util.Arrays.asList(3, 7));
+    assertEquals(resumed, java.util.Collections.singletonList(3));


+    org.mockito.Mockito.when(schemaReader.getKeySchema()).thenReturn(keySchema);
+    org.mockito.Mockito.when(schemaReader.getValueSchema(1)).thenReturn(valueSchema);
+
+    changelogClientConfig = new ChangelogClientConfig<>().setD2ControllerClient(mock(D2ControllerClient.class))
+        .setSchemaReader(schemaReader)
+        .setStoreName(STORE)
+        .setControllerD2ServiceName(D2_SERVICE_NAME)
+        .setD2ServiceName(DEFAULT_CLUSTER_DISCOVERY_D2_SERVICE_NAME)
+        .setConsumerProperties(new Properties())
+        .setLocalD2ZkHosts("test_zookeeper")
+        .setD2Client(mock(D2Client.class))
+        .setVersionSwapByControlMessageEnabled(true)
+        .setClientRegionName(CLIENT_REGION)
+        .setTotalRegionCount(TOTAL_REGIONS);
+    changelogClientConfig.getInnerClientConfig()
+        .setMetricsRepository(getVeniceMetricsRepository(CHANGE_DATA_CAPTURE_CLIENT, CONSUMER_METRIC_ENTITIES, true));
+
+    VeniceChangelogConsumerClientFactory factory =
+        spy(new VeniceChangelogConsumerClientFactory(changelogClientConfig, null));
+    consumer = spy(new VeniceChangelogConsumerDaVinciRecordTransformerImpl<>(changelogClientConfig, factory));
+
+    // Spy stats so we can verify metric emissions
+    stats = spy(consumer.getChangeCaptureStats());
+    consumer.setChangeCaptureStats(stats);
+
+    // Coordinator was initialized with the original (pre-spy) stats reference; rebuild it so its
+    // metric emissions are routed through the spy.
+    consumer.setVersionSwapCoordinator(
+        new RecordTransformerVersionSwapCoordinator(
+            STORE,
+            CLIENT_REGION,
+            TOTAL_REGIONS,
+            changelogClientConfig.getVersionSwapTimeoutInMs(),
+            stats,
+            consumer.getPartitionToVersionToServe(),
+            consumer.getSubscribedPartitions(),
+            consumer.getVersionSwapThreadException()::set));
+
+    currentTransformer = consumer.new DaVinciRecordTransformerChangelogConsumer(STORE, CURRENT_VERSION, keySchema,
+        valueSchema, valueSchema, mock(com.linkedin.davinci.client.DaVinciRecordTransformerConfig.class));
+    futureTransformer = consumer.new DaVinciRecordTransformerChangelogConsumer(STORE, FUTURE_VERSION, keySchema,
+        valueSchema, valueSchema, mock(com.linkedin.davinci.client.DaVinciRecordTransformerConfig.class));
+
+    currentInternal =
+        (InternalDaVinciRecordTransformer<Integer, Integer, Integer>) mock(InternalDaVinciRecordTransformer.class);
+    futureInternal =
+        (InternalDaVinciRecordTransformer<Integer, Integer, Integer>) mock(InternalDaVinciRecordTransformer.class);
+    currentTransformer.setInternalRecordTransformer(currentInternal);
+    futureTransformer.setInternalRecordTransformer(futureInternal);
+
+    // Both partitions assigned and starting on CURRENT_VERSION
+    Map<Integer, Integer> partitionToVersionToServe = consumer.getPartitionToVersionToServe();
+    Set<Integer> subscribed = consumer.getSubscribedPartitions();
+    for (int p = 0; p < TOTAL_REGIONS; p++) {
+      partitionToVersionToServe.put(p, CURRENT_VERSION);
+      subscribed.add(p);
+    }
+  }
+
+  private VersionSwap newVsm(long generationId, String sourceRegion, String destRegion, int oldV, int newV) {
+    VersionSwap vs = new VersionSwap();
+    vs.oldServingVersionTopic = new Utf8(Version.composeKafkaTopic(STORE, oldV));
+    vs.newServingVersionTopic = new Utf8(Version.composeKafkaTopic(STORE, newV));
+    vs.sourceRegion = new Utf8(sourceRegion);
+    vs.destinationRegion = new Utf8(destRegion);
+    vs.generationId = generationId;
+    return vs;
+  }
+
+  @Test
+  public void testOnVersionSwapAaPathPausesCurrentOnPartitionComplete() {
+    VersionSwap fromA = newVsm(1L, CLIENT_REGION, DEST_A, CURRENT_VERSION, FUTURE_VERSION);
+    VersionSwap fromB = newVsm(1L, CLIENT_REGION, DEST_B, CURRENT_VERSION, FUTURE_VERSION);
+
+    // First region — partition 0 not yet complete
+    currentTransformer.onVersionSwap(fromA, CURRENT_VERSION, FUTURE_VERSION, 0);
+    verify(currentInternal, never()).pausePartitionConsumption(0);
+
+    // Second region — partition 0 now complete on current side; pause expected
+    currentTransformer.onVersionSwap(fromB, CURRENT_VERSION, FUTURE_VERSION, 0);
+    verify(currentInternal, times(1)).pausePartitionConsumption(0);
+  }
+
+  @Test
+  public void testOnVersionSwapAaPathPausesFutureOnPartitionComplete() {
+    VersionSwap fromA = newVsm(2L, CLIENT_REGION, DEST_A, CURRENT_VERSION, FUTURE_VERSION);
+    VersionSwap fromB = newVsm(2L, CLIENT_REGION, DEST_B, CURRENT_VERSION, FUTURE_VERSION);
+
+    futureTransformer.onVersionSwap(fromA, CURRENT_VERSION, FUTURE_VERSION, 0);
+    verify(futureInternal, never()).pausePartitionConsumption(0);
+
+    futureTransformer.onVersionSwap(fromB, CURRENT_VERSION, FUTURE_VERSION, 0);
+    verify(futureInternal, times(1)).pausePartitionConsumption(0);
+  }
+
+  @Test
+  public void testOnVersionSwapAaPathDropsForeignRegionVsm() {
+    VersionSwap foreign = newVsm(3L, "different-region", DEST_A, CURRENT_VERSION, FUTURE_VERSION);
+    currentTransformer.onVersionSwap(foreign, CURRENT_VERSION, FUTURE_VERSION, 0);
+    verify(currentInternal, never()).pausePartitionConsumption(0);
+    verify(stats, never()).emitVersionSwapCountMetrics(SUCCESS);
+  }
+
+  @Test
+  public void testOnVersionSwapAaPathDropsLegacyGenerationIdVsm() {
+    VersionSwap legacy = newVsm(-1L, CLIENT_REGION, DEST_A, CURRENT_VERSION, FUTURE_VERSION);
+    currentTransformer.onVersionSwap(legacy, CURRENT_VERSION, FUTURE_VERSION, 0);
+    verify(currentInternal, never()).pausePartitionConsumption(0);
+    verify(stats, never()).emitVersionSwapCountMetrics(SUCCESS);
+  }
+
+  @Test
+  public void testOnVersionSwapAaPathDropsStaleGenerationIdVsm() {
+    VersionSwap firstA = newVsm(10L, CLIENT_REGION, DEST_A, CURRENT_VERSION, FUTURE_VERSION);
+    VersionSwap stale = newVsm(9L, CLIENT_REGION, DEST_B, CURRENT_VERSION, FUTURE_VERSION);
+
+    currentTransformer.onVersionSwap(firstA, CURRENT_VERSION, FUTURE_VERSION, 0);
+    // Stale generation arrives mid-swap — must be ignored
+    currentTransformer.onVersionSwap(stale, CURRENT_VERSION, FUTURE_VERSION, 0);
+    // Only the original region was accumulated; partition not yet complete
+    verify(currentInternal, never()).pausePartitionConsumption(0);
+  }
+
+  @Test
+  public void testOnVersionSwapAaPathDropsStaleRollbackVsm() {
+    Map<Integer, Integer> partitionToVersionToServe = consumer.getPartitionToVersionToServe();
+    // Already serving v6 — rollback re-emitting v3->v4 must be ignored
+    partitionToVersionToServe.put(0, 6);
+    partitionToVersionToServe.put(1, 6);
+
+    VersionSwap rollback = newVsm(50L, CLIENT_REGION, DEST_A, 3, 4);
+    currentTransformer.onVersionSwap(rollback, 3, 4, 0);
+    verify(currentInternal, never()).pausePartitionConsumption(0);
+  }
+
+  @Test
+  public void testOnVersionSwapAaPathFullSwapEmitsSingleSuccessAndFlipsAllPartitions() {
+    VersionSwap fromA = newVsm(20L, CLIENT_REGION, DEST_A, CURRENT_VERSION, FUTURE_VERSION);
+    VersionSwap fromB = newVsm(20L, CLIENT_REGION, DEST_B, CURRENT_VERSION, FUTURE_VERSION);
+
+    for (int p = 0; p < TOTAL_REGIONS; p++) {
+      currentTransformer.onVersionSwap(fromA, CURRENT_VERSION, FUTURE_VERSION, p);
+      currentTransformer.onVersionSwap(fromB, CURRENT_VERSION, FUTURE_VERSION, p);
+      futureTransformer.onVersionSwap(fromA, CURRENT_VERSION, FUTURE_VERSION, p);
+      futureTransformer.onVersionSwap(fromB, CURRENT_VERSION, FUTURE_VERSION, p);
+    }
+
+    Map<Integer, Integer> partitionToVersionToServe = consumer.getPartitionToVersionToServe();
+    for (int p = 0; p < TOTAL_REGIONS; p++) {
+      assertNotNull(partitionToVersionToServe.get(p));
+      org.testng.Assert.assertEquals(partitionToVersionToServe.get(p).intValue(), FUTURE_VERSION);
+    }
+    // Single SUCCESS metric for the entire swap
+    verify(stats, times(1)).emitVersionSwapCountMetrics(SUCCESS);
+    verify(stats, never()).emitVersionSwapCountMetrics(FAIL);
+    // Future side resumed for every partition
+    for (int p = 0; p < TOTAL_REGIONS; p++) {
+      verify(futureInternal, atLeastOnce()).resumePartitionConsumption(p);
+    }
+  }
+
+  @Test
+  public void testOnVersionSwapAaPathFailureSurfacesViaPoll() {
+    // Wrap partitionToVersionToServe in a map that throws on the second put — simulates an
+    // unexpected failure mid-commit. The coordinator catches via failSwap and stashes the exception
+    // so the next poll() throws.
+    java.util.Map<Integer, Integer> throwingMap = new java.util.concurrent.ConcurrentHashMap<Integer, Integer>() {
+      @Override
+      public Integer put(Integer key, Integer value) {
+        throw new IllegalStateException("induced failure during commit");
+      }
+
+      @Override
+      public java.util.Collection<Integer> values() {
+        return java.util.Collections.singletonList(CURRENT_VERSION);
+      }
+    };
+
+    RecordTransformerVersionSwapCoordinator failingCoordinator = new RecordTransformerVersionSwapCoordinator(
+        STORE,
+        CLIENT_REGION,
+        TOTAL_REGIONS,
+        changelogClientConfig.getVersionSwapTimeoutInMs(),
+        stats,
+        throwingMap,
+        consumer.getSubscribedPartitions(),
+        consumer.getVersionSwapThreadException()::set);
+    consumer.setVersionSwapCoordinator(failingCoordinator);
+
+    VersionSwap fromA = newVsm(30L, CLIENT_REGION, DEST_A, CURRENT_VERSION, FUTURE_VERSION);
+    VersionSwap fromB = newVsm(30L, CLIENT_REGION, DEST_B, CURRENT_VERSION, FUTURE_VERSION);
+
+    currentTransformer.onVersionSwap(fromA, CURRENT_VERSION, FUTURE_VERSION, 0);
+    currentTransformer.onVersionSwap(fromB, CURRENT_VERSION, FUTURE_VERSION, 0);
+    currentTransformer.onVersionSwap(fromA, CURRENT_VERSION, FUTURE_VERSION, 1);
+    currentTransformer.onVersionSwap(fromB, CURRENT_VERSION, FUTURE_VERSION, 1);
+    futureTransformer.onVersionSwap(fromA, CURRENT_VERSION, FUTURE_VERSION, 0);
+    futureTransformer.onVersionSwap(fromA, CURRENT_VERSION, FUTURE_VERSION, 1);
+    futureTransformer.onVersionSwap(fromB, CURRENT_VERSION, FUTURE_VERSION, 1);
+    // Last call completes the barrier and triggers commitSwap which throws via the throwing map
+    assertThrows(Exception.class, () -> futureTransformer.onVersionSwap(fromB, CURRENT_VERSION, FUTURE_VERSION, 0));
+
+    verify(stats, times(1)).emitVersionSwapCountMetrics(FAIL);
+    // Next poll() observes the stashed exception
+    assertThrows(VeniceException.class, () -> consumer.poll(1L));


+    for (int partition: assignedPartitionsSnapshot) {
+      partitionToVersionToServe.put(partition, activeNewVersion);


The monolithic TestAaVersionSwapRecordTransformer (~13 min runtime across 7 tests) exceeds the 15-min per-shard CI budget even when given its own shard. Split by topic into two classes that each fit comfortably, and rename to better reflect what's actually under test (the DVRT-based CDC consumer's behavior under AA version swaps, not the RecordTransformer class itself). - AbstractDvrtCdcAaVersionSwapTest — shared multi-region cluster setup, helpers (createAaHybridStore, emptyPush, writeRecords, buildClientConfig, pollUntilRangeObserved, drainForDuration, assertNoLoss, deleteStoreQuietly), and constants. Pattern matches AbstractTestRepush. - TestDvrtCdcAaVersionSwap — single-swap basic + edge scenarios: stateful, stateless, mid-swap restart, watchdog timeout, buffer pressure (~440s). - TestDvrtCdcAaVersionSwapMultiVersion — multi-version scenarios: back-to-back swaps, rollback (~387s). Each subclass lands in its own dedicated shard (86 and 87). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

…ivate SpotBugs MS_PKGPROTECT flagged the protected static final String[] — a mutable array exposed to subclasses in any package. Both concrete subclasses are in the same package, so package-private access is sufficient and silences the warning. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Copilot

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 12 comments.

+      Exception versionSwapException = versionSwapThreadException.get();
+      if (versionSwapException != null) {
+        throw new VeniceException(
+            "Version Swap failed for store: " + storeName + " due to exception:",
+            versionSwapException);
+      }


+  public synchronized boolean recordCurrentVsm(
+      VersionSwap vsm,
+      int partition,
+      InternalDaVinciRecordTransformer<?, ?, ?> currentTransformer) {
+    armIfNeeded(vsm);
+    currentTransformerRef = currentTransformer;
+    if (!assignedPartitionsSnapshot.contains(partition)) {
+      // Partition was added mid-swap; it will be considered on the next swap.
+      return false;
+    }
+    Set<String> regions = currentVersionRegionsConsumed.computeIfAbsent(partition, p -> new HashSet<>());
+    regions.add(vsm.getDestinationRegion().toString());
+    boolean complete = regions.size() >= totalRegionCount;
+    if (complete) {
+      pausedCurrentPartitions.add(partition);
+    }
+    return complete;
+  }
+
+  /**
+   * Records a future-side (new-version) VSM observation for {@code partition}. Returns true when
+   * this partition has now observed one VSM from every destination-region on the future side.
+   */
+  public synchronized boolean recordFutureVsm(
+      VersionSwap vsm,
+      int partition,
+      InternalDaVinciRecordTransformer<?, ?, ?> futureTransformer) {
+    armIfNeeded(vsm);
+    futureTransformerRef = futureTransformer;
+    if (!assignedPartitionsSnapshot.contains(partition)) {
+      return false;
+    }
+    Set<String> regions = futureVersionRegionsConsumed.computeIfAbsent(partition, p -> new HashSet<>());
+    regions.add(vsm.getDestinationRegion().toString());
+    boolean complete = regions.size() >= totalRegionCount;
+    if (complete) {
+      pausedFuturePartitions.add(partition);
+    }
+    return complete;
+  }


+  private void armIfNeeded(VersionSwap vsm) {
+    State current = state.get();
+    if (current == State.IN_PROGRESS) {
+      return;
+    }
+    activeGenerationId = vsm.getGenerationId();
+    activeOldVersionTopic = vsm.getOldServingVersionTopic().toString();
+    activeNewVersionTopic = vsm.getNewServingVersionTopic().toString();
+    activeNewVersion = Version.parseVersionFromVersionTopicName(activeNewVersionTopic);
+    currentVersionRegionsConsumed.clear();
+    futureVersionRegionsConsumed.clear();
+    pausedCurrentPartitions.clear();
+    pausedFuturePartitions.clear();
+    assignedPartitionsSnapshot.clear();
+    assignedPartitionsSnapshot.addAll(subscribedPartitions);
+    state.set(State.IN_PROGRESS);
+    scheduleTimeoutWatchdog();
+  }
+
+  private void scheduleTimeoutWatchdog() {
+    timeoutWatchdog = timeoutExecutor.schedule(this::timeoutSwap, versionSwapTimeoutInMs, TimeUnit.MILLISECONDS);
+  }


+    String oldTopic = vsm.getOldServingVersionTopic().toString();
+    String newTopic = vsm.getNewServingVersionTopic().toString();
+    if (!Version.isVersionTopic(newTopic)) {
+      return false;
+    }


+    Set<String> regions = currentVersionRegionsConsumed.computeIfAbsent(partition, p -> new HashSet<>());
+    regions.add(vsm.getDestinationRegion().toString());
+    boolean complete = regions.size() >= totalRegionCount;
+    if (complete) {
+      pausedCurrentPartitions.add(partition);
+    }
+    return complete;
+  }
+
+  /**
+   * Records a future-side (new-version) VSM observation for {@code partition}. Returns true when
+   * this partition has now observed one VSM from every destination-region on the future side.
+   */
+  public synchronized boolean recordFutureVsm(
+      VersionSwap vsm,
+      int partition,
+      InternalDaVinciRecordTransformer<?, ?, ?> futureTransformer) {
+    armIfNeeded(vsm);
+    futureTransformerRef = futureTransformer;
+    if (!assignedPartitionsSnapshot.contains(partition)) {
+      return false;
+    }
+    Set<String> regions = futureVersionRegionsConsumed.computeIfAbsent(partition, p -> new HashSet<>());
+    regions.add(vsm.getDestinationRegion().toString());


+  protected void deleteStoreQuietly(String storeName) {
+    CompletableFuture.runAsync(() -> {
+      try {
+        parentControllerClient.disableAndDeleteStore(storeName);
+      } catch (Exception e) {
+        LOGGER.debug("Best-effort cleanup of store {} failed", storeName, e);
+      }
+    });
+  }


+    java.util.List<Integer> paused = new java.util.ArrayList<>();
+    java.util.List<Integer> resumed = new java.util.ArrayList<>();
+    internalRecordTransformer.setPartitionPauseHandlers(paused::add, resumed::add);
+
+    internalRecordTransformer.pausePartitionConsumption(3);
+    internalRecordTransformer.pausePartitionConsumption(7);
+    internalRecordTransformer.resumePartitionConsumption(3);
+
+    assertEquals(paused, java.util.Arrays.asList(3, 7));
+    assertEquals(resumed, java.util.Collections.singletonList(3));


+    Schema valueSchema = Schema.create(Schema.Type.INT);
+    org.mockito.Mockito.when(schemaReader.getKeySchema()).thenReturn(keySchema);
+    org.mockito.Mockito.when(schemaReader.getValueSchema(1)).thenReturn(valueSchema);
+
+    changelogClientConfig = new ChangelogClientConfig<>().setD2ControllerClient(mock(D2ControllerClient.class))
+        .setSchemaReader(schemaReader)
+        .setStoreName(STORE)
+        .setControllerD2ServiceName(D2_SERVICE_NAME)
+        .setD2ServiceName(DEFAULT_CLUSTER_DISCOVERY_D2_SERVICE_NAME)
+        .setConsumerProperties(new Properties())
+        .setLocalD2ZkHosts("test_zookeeper")
+        .setD2Client(mock(D2Client.class))
+        .setVersionSwapByControlMessageEnabled(true)
+        .setClientRegionName(CLIENT_REGION)
+        .setTotalRegionCount(TOTAL_REGIONS);
+    changelogClientConfig.getInnerClientConfig()
+        .setMetricsRepository(getVeniceMetricsRepository(CHANGE_DATA_CAPTURE_CLIENT, CONSUMER_METRIC_ENTITIES, true));
+
+    VeniceChangelogConsumerClientFactory factory =
+        spy(new VeniceChangelogConsumerClientFactory(changelogClientConfig, null));
+    consumer = spy(new VeniceChangelogConsumerDaVinciRecordTransformerImpl<>(changelogClientConfig, factory));
+
+    // Spy stats so we can verify metric emissions
+    stats = spy(consumer.getChangeCaptureStats());
+    consumer.setChangeCaptureStats(stats);
+
+    // Coordinator was initialized with the original (pre-spy) stats reference; rebuild it so its
+    // metric emissions are routed through the spy.
+    consumer.setVersionSwapCoordinator(
+        new RecordTransformerVersionSwapCoordinator(
+            STORE,
+            CLIENT_REGION,
+            TOTAL_REGIONS,
+            changelogClientConfig.getVersionSwapTimeoutInMs(),
+            stats,
+            consumer.getPartitionToVersionToServe(),
+            consumer.getSubscribedPartitions(),
+            consumer.getVersionSwapThreadException()::set));
+
+    currentTransformer = consumer.new DaVinciRecordTransformerChangelogConsumer(STORE, CURRENT_VERSION, keySchema,
+        valueSchema, valueSchema, mock(com.linkedin.davinci.client.DaVinciRecordTransformerConfig.class));
+    futureTransformer = consumer.new DaVinciRecordTransformerChangelogConsumer(STORE, FUTURE_VERSION, keySchema,
+        valueSchema, valueSchema, mock(com.linkedin.davinci.client.DaVinciRecordTransformerConfig.class));
+
+    currentInternal =
+        (InternalDaVinciRecordTransformer<Integer, Integer, Integer>) mock(InternalDaVinciRecordTransformer.class);
+    futureInternal =
+        (InternalDaVinciRecordTransformer<Integer, Integer, Integer>) mock(InternalDaVinciRecordTransformer.class);
+    currentTransformer.setInternalRecordTransformer(currentInternal);
+    futureTransformer.setInternalRecordTransformer(futureInternal);
+
+    // Both partitions assigned and starting on CURRENT_VERSION
+    Map<Integer, Integer> partitionToVersionToServe = consumer.getPartitionToVersionToServe();
+    Set<Integer> subscribed = consumer.getSubscribedPartitions();
+    for (int p = 0; p < TOTAL_REGIONS; p++) {
+      partitionToVersionToServe.put(p, CURRENT_VERSION);
+      subscribed.add(p);
+    }
+  }
+
+  private VersionSwap newVsm(long generationId, String sourceRegion, String destRegion, int oldV, int newV) {
+    VersionSwap vs = new VersionSwap();
+    vs.oldServingVersionTopic = new Utf8(Version.composeKafkaTopic(STORE, oldV));
+    vs.newServingVersionTopic = new Utf8(Version.composeKafkaTopic(STORE, newV));
+    vs.sourceRegion = new Utf8(sourceRegion);
+    vs.destinationRegion = new Utf8(destRegion);
+    vs.generationId = generationId;
+    return vs;
+  }
+
+  @Test
+  public void testOnVersionSwapAaPathPausesCurrentOnPartitionComplete() {
+    VersionSwap fromA = newVsm(1L, CLIENT_REGION, DEST_A, CURRENT_VERSION, FUTURE_VERSION);
+    VersionSwap fromB = newVsm(1L, CLIENT_REGION, DEST_B, CURRENT_VERSION, FUTURE_VERSION);
+
+    // First region — partition 0 not yet complete
+    currentTransformer.onVersionSwap(fromA, CURRENT_VERSION, FUTURE_VERSION, 0);
+    verify(currentInternal, never()).pausePartitionConsumption(0);
+
+    // Second region — partition 0 now complete on current side; pause expected
+    currentTransformer.onVersionSwap(fromB, CURRENT_VERSION, FUTURE_VERSION, 0);
+    verify(currentInternal, times(1)).pausePartitionConsumption(0);
+  }
+
+  @Test
+  public void testOnVersionSwapAaPathPausesFutureOnPartitionComplete() {
+    VersionSwap fromA = newVsm(2L, CLIENT_REGION, DEST_A, CURRENT_VERSION, FUTURE_VERSION);
+    VersionSwap fromB = newVsm(2L, CLIENT_REGION, DEST_B, CURRENT_VERSION, FUTURE_VERSION);
+
+    futureTransformer.onVersionSwap(fromA, CURRENT_VERSION, FUTURE_VERSION, 0);
+    verify(futureInternal, never()).pausePartitionConsumption(0);
+
+    futureTransformer.onVersionSwap(fromB, CURRENT_VERSION, FUTURE_VERSION, 0);
+    verify(futureInternal, times(1)).pausePartitionConsumption(0);
+  }
+
+  @Test
+  public void testOnVersionSwapAaPathDropsForeignRegionVsm() {
+    VersionSwap foreign = newVsm(3L, "different-region", DEST_A, CURRENT_VERSION, FUTURE_VERSION);
+    currentTransformer.onVersionSwap(foreign, CURRENT_VERSION, FUTURE_VERSION, 0);
+    verify(currentInternal, never()).pausePartitionConsumption(0);
+    verify(stats, never()).emitVersionSwapCountMetrics(SUCCESS);
+  }
+
+  @Test
+  public void testOnVersionSwapAaPathDropsLegacyGenerationIdVsm() {
+    VersionSwap legacy = newVsm(-1L, CLIENT_REGION, DEST_A, CURRENT_VERSION, FUTURE_VERSION);
+    currentTransformer.onVersionSwap(legacy, CURRENT_VERSION, FUTURE_VERSION, 0);
+    verify(currentInternal, never()).pausePartitionConsumption(0);
+    verify(stats, never()).emitVersionSwapCountMetrics(SUCCESS);
+  }
+
+  @Test
+  public void testOnVersionSwapAaPathDropsStaleGenerationIdVsm() {
+    VersionSwap firstA = newVsm(10L, CLIENT_REGION, DEST_A, CURRENT_VERSION, FUTURE_VERSION);
+    VersionSwap stale = newVsm(9L, CLIENT_REGION, DEST_B, CURRENT_VERSION, FUTURE_VERSION);
+
+    currentTransformer.onVersionSwap(firstA, CURRENT_VERSION, FUTURE_VERSION, 0);
+    // Stale generation arrives mid-swap — must be ignored
+    currentTransformer.onVersionSwap(stale, CURRENT_VERSION, FUTURE_VERSION, 0);
+    // Only the original region was accumulated; partition not yet complete
+    verify(currentInternal, never()).pausePartitionConsumption(0);
+  }
+
+  @Test
+  public void testOnVersionSwapAaPathDropsStaleRollbackVsm() {
+    Map<Integer, Integer> partitionToVersionToServe = consumer.getPartitionToVersionToServe();
+    // Already serving v6 — rollback re-emitting v3->v4 must be ignored
+    partitionToVersionToServe.put(0, 6);
+    partitionToVersionToServe.put(1, 6);
+
+    VersionSwap rollback = newVsm(50L, CLIENT_REGION, DEST_A, 3, 4);
+    currentTransformer.onVersionSwap(rollback, 3, 4, 0);
+    verify(currentInternal, never()).pausePartitionConsumption(0);
+  }
+
+  @Test
+  public void testOnVersionSwapAaPathFullSwapEmitsSingleSuccessAndFlipsAllPartitions() {
+    VersionSwap fromA = newVsm(20L, CLIENT_REGION, DEST_A, CURRENT_VERSION, FUTURE_VERSION);
+    VersionSwap fromB = newVsm(20L, CLIENT_REGION, DEST_B, CURRENT_VERSION, FUTURE_VERSION);
+
+    for (int p = 0; p < TOTAL_REGIONS; p++) {
+      currentTransformer.onVersionSwap(fromA, CURRENT_VERSION, FUTURE_VERSION, p);
+      currentTransformer.onVersionSwap(fromB, CURRENT_VERSION, FUTURE_VERSION, p);
+      futureTransformer.onVersionSwap(fromA, CURRENT_VERSION, FUTURE_VERSION, p);
+      futureTransformer.onVersionSwap(fromB, CURRENT_VERSION, FUTURE_VERSION, p);
+    }
+
+    Map<Integer, Integer> partitionToVersionToServe = consumer.getPartitionToVersionToServe();
+    for (int p = 0; p < TOTAL_REGIONS; p++) {
+      assertNotNull(partitionToVersionToServe.get(p));
+      org.testng.Assert.assertEquals(partitionToVersionToServe.get(p).intValue(), FUTURE_VERSION);
+    }
+    // Single SUCCESS metric for the entire swap
+    verify(stats, times(1)).emitVersionSwapCountMetrics(SUCCESS);
+    verify(stats, never()).emitVersionSwapCountMetrics(FAIL);
+    // Future side resumed for every partition
+    for (int p = 0; p < TOTAL_REGIONS; p++) {
+      verify(futureInternal, atLeastOnce()).resumePartitionConsumption(p);
+    }
+  }
+
+  @Test
+  public void testOnVersionSwapAaPathFailureSurfacesViaPoll() {
+    // Wrap partitionToVersionToServe in a map that throws on the second put — simulates an
+    // unexpected failure mid-commit. The coordinator catches via failSwap and stashes the exception
+    // so the next poll() throws.
+    java.util.Map<Integer, Integer> throwingMap = new java.util.concurrent.ConcurrentHashMap<Integer, Integer>() {
+      @Override
+      public Integer put(Integer key, Integer value) {
+        throw new IllegalStateException("induced failure during commit");
+      }
+
+      @Override
+      public java.util.Collection<Integer> values() {
+        return java.util.Collections.singletonList(CURRENT_VERSION);
+      }
+    };
+
+    RecordTransformerVersionSwapCoordinator failingCoordinator = new RecordTransformerVersionSwapCoordinator(
+        STORE,
+        CLIENT_REGION,
+        TOTAL_REGIONS,
+        changelogClientConfig.getVersionSwapTimeoutInMs(),
+        stats,
+        throwingMap,
+        consumer.getSubscribedPartitions(),
+        consumer.getVersionSwapThreadException()::set);
+    consumer.setVersionSwapCoordinator(failingCoordinator);
+
+    VersionSwap fromA = newVsm(30L, CLIENT_REGION, DEST_A, CURRENT_VERSION, FUTURE_VERSION);
+    VersionSwap fromB = newVsm(30L, CLIENT_REGION, DEST_B, CURRENT_VERSION, FUTURE_VERSION);
+
+    currentTransformer.onVersionSwap(fromA, CURRENT_VERSION, FUTURE_VERSION, 0);
+    currentTransformer.onVersionSwap(fromB, CURRENT_VERSION, FUTURE_VERSION, 0);
+    currentTransformer.onVersionSwap(fromA, CURRENT_VERSION, FUTURE_VERSION, 1);
+    currentTransformer.onVersionSwap(fromB, CURRENT_VERSION, FUTURE_VERSION, 1);
+    futureTransformer.onVersionSwap(fromA, CURRENT_VERSION, FUTURE_VERSION, 0);
+    futureTransformer.onVersionSwap(fromA, CURRENT_VERSION, FUTURE_VERSION, 1);
+    futureTransformer.onVersionSwap(fromB, CURRENT_VERSION, FUTURE_VERSION, 1);
+    // Last call completes the barrier and triggers commitSwap which throws via the throwing map
+    assertThrows(Exception.class, () -> futureTransformer.onVersionSwap(fromB, CURRENT_VERSION, FUTURE_VERSION, 0));
+
+    verify(stats, times(1)).emitVersionSwapCountMetrics(FAIL);
+    // Next poll() observes the stashed exception
+    assertThrows(VeniceException.class, () -> consumer.poll(1L));


+  private void flipServingVersion() {
+    for (int partition: assignedPartitionsSnapshot) {
+      partitionToVersionToServe.put(partition, activeNewVersion);
+    }
+  }


+        throw new VeniceException(
+            "Version Swap failed for store: " + storeName + " due to exception:",
+            versionSwapException);


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kvargha changed the title ~~[dvc][cc] Add cross-region version-swap coordinator for AA DVRT CDC~~ [dvc][cc] Handle new A/A version swap messages in DVRT CDC consumer May 13, 2026

kvargha changed the title ~~[dvc][cc] Handle new A/A version swap messages in DVRT CDC consumer~~ [dvc][cc] Fix unsafe DVRT CDC version swap May 13, 2026

kvargha and others added 2 commits May 13, 2026 16:32

Merge remote-tracking branch 'upstream/main' into

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worktree-dvrt-cdc-aa-version-swap

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[dvc][cc] Fix unsafe DVRT CDC version swap#2795

[dvc][cc] Fix unsafe DVRT CDC version swap#2795
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kvargha:worktree-dvrt-cdc-aa-version-swap

kvargha commented May 13, 2026 •

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		this.timeoutExecutor = Executors.newSingleThreadScheduledExecutor(
		new DaemonThreadFactory("RecordTransformerVersionSwapCoordinator-" + storeName));

		for (int partition: assignedPartitionsSnapshot) {
		partitionToVersionToServe.put(partition, activeNewVersion);

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kvargha commented May 13, 2026 •

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