[GitHub] [helix] qqu0127 commented on a diff in pull request #2447: WAGED rebalance overwrite redesign -- part 2

["qqu0127 (via GitHub)" <gi...@apache.org>]

qqu0127 commented on code in PR #2447:
URL: https://github.com/apache/helix/pull/2447#discussion_r1171705756


##########
helix-core/src/main/java/org/apache/helix/controller/rebalancer/util/DelayedRebalanceUtil.java:
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@@ -335,6 +335,42 @@ public static Set<AssignableReplica> findToBeAssignedReplicasForMinActiveReplica
     return toBeAssignedReplicas;
   }
 
+  /**
+   * Merge entries from currentResourceAssignment to newAssignment.
+   * To handle minActiveReplica for delayed rebalance, new assignment is computed based on enabled live instances, but
+   * could miss out current partition allocation still on offline instances (within delayed window).
+   * The merge process is independent for each resource; for each resource-partition, it adds the <instance, state> pair
+   * to newAssignment if it's not there yet; in other word, the entries in newAssignment won't be override.
+   * @param newAssignment newAssignment to merge, this map is getting updated during this method.
+   * @param currentResourceAssignment the current resource assignment
+   * @param enabledLiveInstances the set of enabled live instance
+   */
+  public static void mergeAssignments(Map<String, ResourceAssignment> newAssignment,
+      Map<String, ResourceAssignment> currentResourceAssignment,
+      Set<String> enabledLiveInstances) {
+    // merge with current assignment for partitions assigned on rest of the instances (not immediately live)
+    currentResourceAssignment.entrySet().parallelStream().forEach(entry -> {
+      String resourceName = entry.getKey();
+      ResourceAssignment currentAssignment = entry.getValue();
+      for (Partition partition : currentAssignment.getMappedPartitions()) {
+        currentAssignment.getReplicaMap(partition).entrySet().stream() // <instance, state>
+            // the existing partitions on the enabledLiveInstances are pre-allocated, only process for the rest
+            .filter(e -> !enabledLiveInstances.contains(e.getKey()) ||
+                !newAssignment.containsKey(resourceName) ||
+                !newAssignment.get(resourceName).getReplicaMap(partition).containsKey(e.getKey()))

Review Comment:
   It's a little complicated. The computed assignment contains both existing allocation and the newly computed assignment, BUT, that only apply to the "assignable" nodes, in this case, only the immediate live nodes.
   Some unit tests are using https://github.com/apache/helix/blob/master/helix-core/src/test/java/org/apache/helix/controller/rebalancer/waged/constraints/MockRebalanceAlgorithm.java that doesn't assign current allocation, and it's confusing sometime.



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