HelixAdmin APIs and pipeline changes to support Helix Node Swap

helix-core/src/main/java/org/apache/helix/HelixAdmin.java

@@ -23,6 +23,8 @@
 import java.util.List;
 import java.util.Map;
 
+import javax.annotation.Nullable;
+
 import org.apache.helix.api.status.ClusterManagementMode;
 import org.apache.helix.api.status.ClusterManagementModeRequest;
 import org.apache.helix.api.topology.ClusterTopology;
@@ -302,8 +304,15 @@ void enableInstance(String clusterName, String instanceName, boolean enabled,
    */
   void enableInstance(String clusterName, List<String> instances, boolean enabled);
 
-  void setInstanceOperation(String clusterName, String instance,
-      InstanceConstants.InstanceOperation instanceOperation);
+  /**
+   * Set the instanceOperation field.
+   *
+   * @param clusterName       The cluster name
+   * @param instanceName      The instance name
+   * @param instanceOperation The instance operation
+   */
+  void setInstanceOperation(String clusterName, String instanceName,
+      @Nullable InstanceConstants.InstanceOperation instanceOperation);
 
   /**
    * Disable or enable a resource
@@ -747,6 +756,26 @@ Map<String, Boolean> validateInstancesForWagedRebalance(String clusterName,
    */
   boolean isEvacuateFinished(String clusterName, String instancesNames);
 
+  /**
+   * Check to see if swapping between two instances can be completed. Either the swapOut or
+   * swapIn instance can be passed in.
+   * @param clusterName  The cluster name
+   * @param instanceName The instance that is being swapped out or swapped in
+   * @return True if the swap is ready to be completed, false otherwise.
+   */
+  boolean canSwapBeCompleted(String clusterName, String instanceName);
+
+  /**
+   * Check to see if swapping between two instances is ready to be completed and complete it if
+   * possible. Either the swapOut or swapIn instance can be passed in.
+   *
+   * @param clusterName  The cluster name
+   * @param instanceName The instance that is being swapped out or swapped in
+   * @return True if the swap is ready to be completed and was completed successfully, false
+   * otherwise.
+   */
+  boolean completeSwapIfPossible(String clusterName, String instanceName);
+
   /**
    * Return if instance is ready for preparing joining cluster. The instance should have no current state,
    * no pending message and tagged with operation that exclude the instance from Helix assignment.

helix-core/src/main/java/org/apache/helix/controller/dataproviders/BaseControllerDataProvider.java

@@ -46,10 +46,12 @@
 import org.apache.helix.common.caches.PropertyCache;
 import org.apache.helix.common.caches.TaskCurrentStateCache;
 import org.apache.helix.common.controllers.ControlContextProvider;
+import org.apache.helix.constants.InstanceConstants;
 import org.apache.helix.controller.LogUtil;
 import org.apache.helix.controller.rebalancer.constraint.MonitoredAbnormalResolver;
 import org.apache.helix.model.ClusterConfig;
 import org.apache.helix.model.ClusterConstraints;
+import org.apache.helix.model.ClusterTopologyConfig;
 import org.apache.helix.model.CurrentState;
 import org.apache.helix.model.IdealState;
 import org.apache.helix.model.InstanceConfig;
@@ -116,6 +118,8 @@ public class BaseControllerDataProvider implements ControlContextProvider {
   private Map<String, Map<String, String>> _idealStateRuleMap;
   private final Map<String, Map<String, Set<String>>> _disabledInstanceForPartitionMap = new HashMap<>();
   private final Set<String> _disabledInstanceSet = new HashSet<>();
+  private final Map<String, String> _swapOutInstanceNameToSwapInInstanceName = new HashMap<>();
+  private final Set<String> _enabledLiveSwapInInstanceNames = new HashSet<>();
   private final Map<String, MonitoredAbnormalResolver> _abnormalStateResolverMap = new HashMap<>();
   private final Set<String> _timedOutInstanceDuringMaintenance = new HashSet<>();
   private Map<String, LiveInstance> _liveInstanceExcludeTimedOutForMaintenance = new HashMap<>();
@@ -437,6 +441,8 @@ protected synchronized Set<HelixConstants.ChangeType> doRefresh(HelixDataAccesso
 
     updateIdealRuleMap(getClusterConfig());
     updateDisabledInstances(getInstanceConfigMap().values(), getClusterConfig());
+    updateSwappingInstances(getInstanceConfigMap().values(), getEnabledLiveInstances(),
+        getClusterConfig());
 
     return refreshedTypes;
   }
@@ -471,6 +477,8 @@ public void setClusterConfig(ClusterConfig clusterConfig) {
     refreshAbnormalStateResolverMap(_clusterConfig);
     updateIdealRuleMap(_clusterConfig);
     updateDisabledInstances(getInstanceConfigMap().values(), _clusterConfig);
+    updateSwappingInstances(getInstanceConfigMap().values(), getEnabledLiveInstances(),
+        _clusterConfig);
   }
 
   @Override
@@ -617,6 +625,24 @@ public Set<String> getDisabledInstances() {
     return Collections.unmodifiableSet(_disabledInstanceSet);
   }
 
+  /**
+   * Get all swapping instance pairs.
+   *
+   * @return a map of SWAP_OUT instanceNames and their corresponding SWAP_IN instanceNames.
+   */
+  public Map<String, String> getSwapOutToSwapInInstancePairs() {
+    return Collections.unmodifiableMap(_swapOutInstanceNameToSwapInInstanceName);
+  }
+
+  /**
+   * Get all the enabled and live SWAP_IN instances.
+   *
+   * @return a set of SWAP_IN instanceNames that have a corresponding SWAP_OUT instance.
+   */
+  public Set<String> getEnabledLiveSwapInInstanceNames() {
+    return Collections.unmodifiableSet(_enabledLiveSwapInInstanceNames);
+  }
+
   public synchronized void setLiveInstances(List<LiveInstance> liveInstances) {
     _liveInstanceCache.setPropertyMap(HelixProperty.convertListToMap(liveInstances));
     _updateInstanceOfflineTime = true;
@@ -750,6 +776,8 @@ public Map<String, InstanceConfig> getInstanceConfigMap() {
   public void setInstanceConfigMap(Map<String, InstanceConfig> instanceConfigMap) {
     _instanceConfigCache.setPropertyMap(instanceConfigMap);
     updateDisabledInstances(instanceConfigMap.values(), getClusterConfig());
+    updateSwappingInstances(instanceConfigMap.values(), getEnabledLiveInstances(),
+        getClusterConfig());
   }
 
   /**
@@ -858,6 +886,42 @@ private void updateDisabledInstances(Collection<InstanceConfig> instanceConfigs,
     }
   }
 
+  private void updateSwappingInstances(Collection<InstanceConfig> instanceConfigs,
+      Set<String> liveEnabledInstances, ClusterConfig clusterConfig) {
+    ClusterTopologyConfig clusterTopologyConfig =
+        ClusterTopologyConfig.createFromClusterConfig(clusterConfig);
+    _swapOutInstanceNameToSwapInInstanceName.clear();
+    _enabledLiveSwapInInstanceNames.clear();
+    Map<String, String> swapOutLogicalIdsByInstanceName = new HashMap<>();
+    Map<String, String> swapInInstancesByLogicalId = new HashMap<>();
+    instanceConfigs.forEach(instanceConfig -> {
+      if (instanceConfig == null) {
+        return;
+      }
+      if (instanceConfig.getInstanceOperation()
+          .equals(InstanceConstants.InstanceOperation.SWAP_OUT.name())) {
+        swapOutLogicalIdsByInstanceName.put(instanceConfig.getInstanceName(),
+            instanceConfig.getLogicalId(clusterTopologyConfig.getEndNodeType()));
+      }
+      if (instanceConfig.getInstanceOperation()
+          .equals(InstanceConstants.InstanceOperation.SWAP_IN.name())) {
+        swapInInstancesByLogicalId.put(
+            instanceConfig.getLogicalId(clusterTopologyConfig.getEndNodeType()),
+            instanceConfig.getInstanceName());
+      }
+    });
+
+    swapOutLogicalIdsByInstanceName.forEach((swapOutInstanceName, value) -> {
+      String swapInInstanceName = swapInInstancesByLogicalId.get(value);
+      if (swapInInstanceName != null) {
+        _swapOutInstanceNameToSwapInInstanceName.put(swapOutInstanceName, swapInInstanceName);
+        if (liveEnabledInstances.contains(swapInInstanceName)) {
+          _enabledLiveSwapInInstanceNames.add(swapInInstanceName);
+        }
+      }
+    });
+  }
+
   /*
    * Check if the instance is timed-out during maintenance mode. An instance is timed-out if it has
    * been offline for longer than the user defined timeout window.

helix-core/src/main/java/org/apache/helix/controller/rebalancer/DelayedAutoRebalancer.java

@@ -31,17 +31,17 @@
 import java.util.Optional;
 import java.util.Set;
 
-import java.util.stream.Collectors;
 import org.apache.helix.HelixDefinedState;
 import org.apache.helix.api.config.StateTransitionThrottleConfig;
+import org.apache.helix.constants.InstanceConstants;
 import org.apache.helix.controller.dataproviders.ResourceControllerDataProvider;
 import org.apache.helix.controller.rebalancer.constraint.MonitoredAbnormalResolver;
 import org.apache.helix.controller.rebalancer.util.DelayedRebalanceUtil;
 import org.apache.helix.controller.rebalancer.util.WagedValidationUtil;
 import org.apache.helix.controller.stages.CurrentStateOutput;
 import org.apache.helix.model.ClusterConfig;
+import org.apache.helix.model.ClusterTopologyConfig;
 import org.apache.helix.model.IdealState;
-import org.apache.helix.model.InstanceConfig;
 import org.apache.helix.model.Partition;
 import org.apache.helix.model.Resource;
 import org.apache.helix.model.ResourceAssignment;
@@ -56,7 +56,8 @@
  */
 public class DelayedAutoRebalancer extends AbstractRebalancer<ResourceControllerDataProvider> {
   private static final Logger LOG = LoggerFactory.getLogger(DelayedAutoRebalancer.class);
-   public static final Set<String> INSTANCE_OPERATION_TO_EXCLUDE_FROM_ASSIGNMENT = ImmutableSet.of("EVACUATE", "SWAP_IN");
+  public static ImmutableSet<String> INSTANCE_OPERATION_TO_EXCLUDE_FROM_ASSIGNMENT =
+      ImmutableSet.of(InstanceConstants.InstanceOperation.EVACUATE.name());
 
   @Override
   public IdealState computeNewIdealState(String resourceName,
@@ -113,9 +114,16 @@ public IdealState computeNewIdealState(String resourceName,
       allNodes = clusterData.getAllInstances();
     }
 
+    Set<String> allNodesDeduped = DelayedRebalanceUtil.filterOutInstancesWithDuplicateLogicalIds(
+        ClusterTopologyConfig.createFromClusterConfig(clusterConfig),
+        clusterData.getInstanceConfigMap(), allNodes);
+    // Remove the non-selected instances with duplicate logicalIds from liveEnabledNodes
+    // This ensures the same duplicate instance is kept in both allNodesDeduped and liveEnabledNodes
+    liveEnabledNodes.retainAll(allNodesDeduped);
+
     long delay = DelayedRebalanceUtil.getRebalanceDelay(currentIdealState, clusterConfig);
     Set<String> activeNodes = DelayedRebalanceUtil
-        .getActiveNodes(allNodes, currentIdealState, liveEnabledNodes,
+        .getActiveNodes(allNodesDeduped, currentIdealState, liveEnabledNodes,
             clusterData.getInstanceOfflineTimeMap(), clusterData.getLiveInstances().keySet(),
             clusterData.getInstanceConfigMap(), delay, clusterConfig);
     if (delayRebalanceEnabled) {
@@ -127,11 +135,11 @@ public IdealState computeNewIdealState(String resourceName,
           clusterConfig, _manager);
     }
 
-    if (allNodes.isEmpty() || activeNodes.isEmpty()) {
+    if (allNodesDeduped.isEmpty() || activeNodes.isEmpty()) {
       LOG.error(String.format(
           "No instances or active instances available for resource %s, "
               + "allInstances: %s, liveInstances: %s, activeInstances: %s",
-          resourceName, allNodes, liveEnabledNodes, activeNodes));
+          resourceName, allNodesDeduped, liveEnabledNodes, activeNodes));
       return generateNewIdealState(resourceName, currentIdealState,
           emptyMapping(currentIdealState));
     }
@@ -158,40 +166,56 @@ public IdealState computeNewIdealState(String resourceName,
             stateCountMap, maxPartition);
 
     // sort node lists to ensure consistent preferred assignments
-    List<String> allNodeList = new ArrayList<>(allNodes);
+    List<String> allNodeList = new ArrayList<>(allNodesDeduped);
     // We will not assign partition to instances with evacuation and wap-out tag.
     // TODO: Currently we have 2 groups of instances and compute preference list twice and merge.
     // Eventually we want to have exclusive groups of instance for different instance tag.
-    List<String> liveEnabledAssignableNodeList = filterOutOnOperationInstances(clusterData.getInstanceConfigMap(),
-        liveEnabledNodes);
+    List<String> liveEnabledAssignableNodeList = new ArrayList<>(
+        DelayedRebalanceUtil.filterOutEvacuatingInstances(clusterData.getInstanceConfigMap(),
+            liveEnabledNodes));
     Collections.sort(allNodeList);
     Collections.sort(liveEnabledAssignableNodeList);
 
-    ZNRecord newIdealMapping = _rebalanceStrategy
-        .computePartitionAssignment(allNodeList, liveEnabledAssignableNodeList, currentMapping, clusterData);
+    ZNRecord newIdealMapping =
+        _rebalanceStrategy.computePartitionAssignment(allNodeList, liveEnabledAssignableNodeList,
+            currentMapping, clusterData);
     ZNRecord finalMapping = newIdealMapping;
 
     if (DelayedRebalanceUtil.isDelayRebalanceEnabled(currentIdealState, clusterConfig)
-        || liveEnabledAssignableNodeList.size()!= activeNodes.size()) {
+        || liveEnabledAssignableNodeList.size() != activeNodes.size()) {
       List<String> activeNodeList = new ArrayList<>(activeNodes);
       Collections.sort(activeNodeList);
       int minActiveReplicas = DelayedRebalanceUtil.getMinActiveReplica(
           ResourceConfig.mergeIdealStateWithResourceConfig(resourceConfig, currentIdealState),
           currentIdealState, replicaCount);
 
-      ZNRecord newActiveMapping = _rebalanceStrategy
-          .computePartitionAssignment(allNodeList, activeNodeList, currentMapping, clusterData);
+      ZNRecord newActiveMapping =
+          _rebalanceStrategy.computePartitionAssignment(allNodeList, activeNodeList, currentMapping,
+              clusterData);
       finalMapping = getFinalDelayedMapping(currentIdealState, newIdealMapping, newActiveMapping,
           liveEnabledNodes, replicaCount, minActiveReplicas);
     }
 
     finalMapping.getListFields().putAll(userDefinedPreferenceList);
 
+    // 1. Get all SWAP_OUT instances and corresponding SWAP_IN instance pairs in the cluster.
+    Map<String, String> swapOutToSwapInInstancePairs =
+        clusterData.getSwapOutToSwapInInstancePairs();
+    // 2. Get all enabled and live SWAP_IN instances in the cluster.
+    Set<String> enabledLiveSwapInInstances = clusterData.getEnabledLiveSwapInInstanceNames();
+    // 3. For each SWAP_OUT instance in any of the preferenceLists, add the corresponding SWAP_IN instance to the end.
+    // Skipping this when there are not SWAP_IN instances ready(enabled and live) will reduce computation time when there is not an active
+    // swap occurring.
+    if (!clusterData.getEnabledLiveSwapInInstanceNames().isEmpty()) {
+      DelayedRebalanceUtil.addSwapInInstanceToPreferenceListsIfSwapOutInstanceExists(finalMapping,
+          swapOutToSwapInInstancePairs, enabledLiveSwapInInstances);
+    }
+
     LOG.debug("currentMapping: {}", currentMapping);
     LOG.debug("stateCountMap: {}", stateCountMap);
     LOG.debug("liveEnabledNodes: {}", liveEnabledNodes);
     LOG.debug("activeNodes: {}", activeNodes);
-    LOG.debug("allNodes: {}", allNodes);
+    LOG.debug("allNodes: {}", allNodesDeduped);
     LOG.debug("maxPartition: {}", maxPartition);
     LOG.debug("newIdealMapping: {}", newIdealMapping);
     LOG.debug("finalMapping: {}", finalMapping);
@@ -201,14 +225,6 @@ public IdealState computeNewIdealState(String resourceName,
     return idealState;
   }
 
-  private static List<String> filterOutOnOperationInstances(Map<String, InstanceConfig> instanceConfigMap,
-      Set<String> nodes) {
-    return nodes.stream()
-        .filter(
-            instance -> !INSTANCE_OPERATION_TO_EXCLUDE_FROM_ASSIGNMENT.contains(instanceConfigMap.get(instance).getInstanceOperation()))
-        .collect(Collectors.toList());
-  }
-
   private IdealState generateNewIdealState(String resourceName, IdealState currentIdealState,
       ZNRecord newMapping) {
     IdealState newIdealState = new IdealState(resourceName);
@@ -376,7 +392,7 @@ protected Map<String, String> computeBestPossibleStateForPartition(Set<String> l
     // if preference list is not empty, and we do have new intanceToAdd, we
     // should check if it has capacity to hold the partition.
     boolean isWaged = WagedValidationUtil.isWagedEnabled(idealState) && cache != null;
-    if (isWaged && !isPreferenceListEmpty && instanceToAdd.size() > 0) {
+    if (isWaged && !isPreferenceListEmpty && !instanceToAdd.isEmpty()) {
       // check instanceToAdd instance appears in combinedPreferenceList
       for (String instance : instanceToAdd) {
         if (combinedPreferenceList.contains(instance)) {
@@ -409,7 +425,11 @@ protected Map<String, String> computeBestPossibleStateForPartition(Set<String> l
         bestPossibleStateMap, preferenceList, combinedPreferenceList)) {
       for (int i = 0; i < combinedPreferenceList.size() - numReplicas; i++) {
         String instanceToDrop = combinedPreferenceList.get(combinedPreferenceList.size() - i - 1);
-        bestPossibleStateMap.put(instanceToDrop, HelixDefinedState.DROPPED.name());
+        // We do not want to drop a SWAP_IN node if it is at the end of the preferenceList,
+        // because partitions are actively being added on this node to prepare for SWAP completion.
+        if (cache == null || !cache.getEnabledLiveSwapInInstanceNames().contains(instanceToDrop)) {
+          bestPossibleStateMap.put(instanceToDrop, HelixDefinedState.DROPPED.name());
+        }
       }
     }