[GitHub] [incubator-pinot] jackjlli commented on a change in pull request #4553: Refactor ControllerLeaderLocator

[GitBox <gi...@apache.org>]

jackjlli commented on a change in pull request #4553: Refactor ControllerLeaderLocator
URL: https://github.com/apache/incubator-pinot/pull/4553#discussion_r324379250
 
 

 ##########
 File path: pinot-core/src/main/java/org/apache/pinot/server/realtime/ControllerLeaderLocator.java
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 @@ -80,45 +84,111 @@ public static ControllerLeaderLocator getInstance() {
 
   /**
    * Locates the controller leader so that we can send LLC segment completion requests to it.
-   * Checks the {@link ControllerLeaderLocator::_cachedControllerLeaderInvalid} flag and fetches the leader from helix if cached value is invalid
+   * Checks the {@link ControllerLeaderLocator::_cachedControllerLeaderInvalid} flag and fetches the leaders to {@link ControllerLeaderLocator::_cachedControllerLeaderMap} from helix if cached value is invalid
    * @param rawTableName table name without type.
    * @return The host-port pair of the current controller leader.
    */
   public synchronized Pair<String, Integer> getControllerLeader(String rawTableName) {
+    int partitionId = LeadControllerUtils.getPartitionIdForTable(rawTableName);
     if (!_cachedControllerLeaderInvalid) {
-      return _controllerLeaderHostPort;
+      return _cachedControllerLeaderMap.get(partitionId);
     }
 
-    Pair<String, Integer> leaderForTable = getLeaderForTable(rawTableName);
-    if (leaderForTable == null) {
-      LOGGER.warn("Failed to find a leader for Table: {}", rawTableName);
+    // No controller leader cached, fetches a fresh copy of external view and then gets the leader for the given table.
+    boolean success = refreshControllerLeaderMap();
+    if (success) {
+      _cachedControllerLeaderInvalid = false;
+      LOGGER.info("Refreshed controller leader map successfully.");
+      return _cachedControllerLeaderMap.get(partitionId);
+    } else {
       _cachedControllerLeaderInvalid = true;
+      LOGGER.warn("Failed to refresh controller leader map.");
       return null;
-    } else {
-      _controllerLeaderHostPort = leaderForTable;
-      _cachedControllerLeaderInvalid = false;
-      LOGGER.info("Setting controller leader to be {}:{}", _controllerLeaderHostPort.getFirst(),
-          _controllerLeaderHostPort.getSecond());
-      return _controllerLeaderHostPort;
     }
   }
 
   /**
-   * Firstly checks whether lead controller resource has been enabled or not.
-   * If yes, use this as the leader for realtime segment completion once partition leader exists.
-   * Otherwise, try to use Helix leader.
-   * @param rawTableName table name without type.
-   * @return the controller leader id with hostname and port for this table, e.g. localhost_9000
+   * Checks whether lead controller resource has been enabled or not.
+   * If yes, updates lead controller pairs from the external view of lead controller resource.
+   * Otherwise, updates lead controller pairs from Helix cluster leader.
+   * @return true if refresh is completed successfully.
    */
-  private Pair<String, Integer> getLeaderForTable(String rawTableName) {
+  private boolean refreshControllerLeaderMap() {
     // Checks whether lead controller resource has been enabled or not.
     if (isLeadControllerResourceEnabled()) {
-      // Gets leader from lead controller resource.
-      return getLeaderFromLeadControllerResource(rawTableName);
+      return refreshControllerLeaderMapFromLeadControllerResource();
     } else {
-      // Gets Helix leader to be the leader to this table, otherwise returns null.
-      return getHelixClusterLeader();
+      return refreshControllerLeaderMapFromHelixClusterLeader();
+    }
+  }
+
+  /**
+   * Updates lead controller pairs from the external view of lead controller resource.
+   * @return true if refresh is completed successfully, false if no leader found or exception thrown.
+   */
+  private boolean refreshControllerLeaderMapFromLeadControllerResource() {
+    try {
+      ExternalView leadControllerResourceExternalView = _helixManager.getClusterManagmentTool()
+          .getResourceExternalView(_helixManager.getClusterName(), CommonConstants.Helix.LEAD_CONTROLLER_RESOURCE_NAME);
+      if (leadControllerResourceExternalView == null) {
+        LOGGER.warn("External view of lead controller resource is null.");
+        return false;
+      }
+      Set<String> partitionNames = leadControllerResourceExternalView.getPartitionSet();
+      if (partitionNames.isEmpty()) {
+        LOGGER.warn("The partition set of lead controller resource is empty.");
+        return false;
+      }
+      if (partitionNames.size() != CommonConstants.Helix.NUMBER_OF_PARTITIONS_IN_LEAD_CONTROLLER_RESOURCE) {
+        LOGGER.warn("The partition size of lead controller resource isn't {}. Actual size: {}",
+            CommonConstants.Helix.NUMBER_OF_PARTITIONS_IN_LEAD_CONTROLLER_RESOURCE, partitionNames.size());
+        return false;
+      }
+      for (String partitionName : partitionNames) {
+        int partitionId = LeadControllerUtils.extractPartitionId(partitionName);
+        Map<String, String> partitionStateMap = leadControllerResourceExternalView.getStateMap(partitionName);
+        boolean masterFound = false;
+        // Get master host from partition map. Return null if no master found.
+        for (Map.Entry<String, String> entry : partitionStateMap.entrySet()) {
+          if (MasterSlaveSMD.States.MASTER.name().equals(entry.getValue())) {
+            // Found the controller in master state.
+            // Converts participant id (with Prefix "Controller_") to controller id and assigns it as the leader,
+            // since realtime segment completion protocol doesn't need the prefix in controller instance id.
+            String participantInstanceId = entry.getKey();
 
 Review comment:
   No, in this PR only Pinot server needs to fetch the external view. 

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