[GitHub] gianm closed pull request #5974: [Backport] Coordinator fix balance to try to move max segments instead of up to max segments

[GitBox]

gianm closed pull request #5974: [Backport] Coordinator fix balance to try to 
move max segments instead of up to max segments
URL: https://github.com/apache/incubator-druid/pull/5974
 
 
   

This is a PR merged from a forked repository.
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diff --git 
a/server/src/main/java/io/druid/server/coordinator/helper/DruidCoordinatorBalancer.java
 
b/server/src/main/java/io/druid/server/coordinator/helper/DruidCoordinatorBalancer.java
index cc266d705df..b4f7e22411f 100644
--- 
a/server/src/main/java/io/druid/server/coordinator/helper/DruidCoordinatorBalancer.java
+++ 
b/server/src/main/java/io/druid/server/coordinator/helper/DruidCoordinatorBalancer.java
@@ -20,9 +20,9 @@
 package io.druid.server.coordinator.helper;
 
 import com.google.common.collect.Lists;
-import io.druid.java.util.emitter.EmittingLogger;
 import io.druid.client.ImmutableDruidServer;
 import io.druid.java.util.common.StringUtils;
+import io.druid.java.util.emitter.EmittingLogger;
 import io.druid.server.coordinator.BalancerSegmentHolder;
 import io.druid.server.coordinator.BalancerStrategy;
 import io.druid.server.coordinator.CoordinatorStats;
@@ -40,6 +40,7 @@
 import java.util.NavigableSet;
 import java.util.SortedSet;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.stream.Collectors;
 
 /**
  */
@@ -103,15 +104,16 @@ private void balanceTier(
       return;
     }
 
-    final List<ServerHolder> serverHolderList = Lists.newArrayList(servers);
+    final List<ServerHolder> toMoveFrom = Lists.newArrayList(servers);
+    final List<ServerHolder> toMoveTo = Lists.newArrayList(servers);
 
-    if (serverHolderList.size() <= 1) {
+    if (toMoveTo.size() <= 1) {
       log.info("[%s]: One or fewer servers found.  Cannot balance.", tier);
       return;
     }
 
     int numSegments = 0;
-    for (ServerHolder server : serverHolderList) {
+    for (ServerHolder server : toMoveFrom) {
       numSegments += server.getServer().getSegments().size();
     }
 
@@ -119,20 +121,31 @@ private void balanceTier(
       log.info("No segments found.  Cannot balance.");
       return;
     }
+
+    final int maxToLoad = 
params.getCoordinatorDynamicConfig().getMaxSegmentsInNodeLoadingQueue();
     long unmoved = 0L;
-    for (int iter = 0; iter < maxSegmentsToMove; iter++) {
-      final BalancerSegmentHolder segmentToMove = 
strategy.pickSegmentToMove(serverHolderList);
+    for (int moved = 0; (moved + unmoved) < maxSegmentsToMove;) {
+      final BalancerSegmentHolder segmentToMove = 
strategy.pickSegmentToMove(toMoveFrom);
 
       if (segmentToMove != null && 
params.getAvailableSegments().contains(segmentToMove.getSegment())) {
-        final ServerHolder holder = 
strategy.findNewSegmentHomeBalancer(segmentToMove.getSegment(), 
serverHolderList);
+        final List<ServerHolder> toMoveToWithLoadQueueCapacity =
+            toMoveTo.stream()
+                    .filter(s -> maxToLoad <= 0 || 
s.getNumberOfSegmentsInQueue() < maxToLoad)
+                    .collect(Collectors.toList());
 
-        if (holder != null) {
-          moveSegment(segmentToMove, holder.getServer(), params);
+        final ServerHolder destinationHolder =
+            strategy.findNewSegmentHomeBalancer(segmentToMove.getSegment(), 
toMoveToWithLoadQueueCapacity);
+
+        if (destinationHolder != null) {
+          moveSegment(segmentToMove, destinationHolder.getServer(), params);
+          moved++;
         } else {
-          ++unmoved;
+          log.info("Segment [%s] is 'optimally' placed.", 
segmentToMove.getSegment().getIdentifier());
+          unmoved++;
         }
       }
     }
+
     if (unmoved == maxSegmentsToMove) {
       // Cluster should be alive and constantly adjusting
       log.info("No good moves found in tier [%s]", tier);
@@ -140,7 +153,7 @@ private void balanceTier(
     stats.addToTieredStat("unmovedCount", tier, unmoved);
     stats.addToTieredStat("movedCount", tier, 
currentlyMovingSegments.get(tier).size());
     if (params.getCoordinatorDynamicConfig().emitBalancingStats()) {
-      strategy.emitStats(tier, stats, serverHolderList);
+      strategy.emitStats(tier, stats, toMoveFrom);
     }
     log.info(
         "[%s]: Segments Moved: [%d] Segments Let Alone: [%d]",


 

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