[GitHub] [hadoop-ozone] timmylicheng commented on a change in pull request #668: HDDS-3139 Pipeline placement should max out pipeline usage

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timmylicheng commented on a change in pull request #668: HDDS-3139 Pipeline placement should max out pipeline usage
URL: https://github.com/apache/hadoop-ozone/pull/668#discussion_r396229970
 
 

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 File path: hadoop-hdds/server-scm/src/main/java/org/apache/hadoop/hdds/scm/pipeline/PipelinePlacementPolicy.java
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 @@ -315,6 +314,50 @@ DatanodeDetails fallBackPickNodes(
     return results;
   }
 
+  private DatanodeDetails randomPick(List<DatanodeDetails> healthyNodes) {
+    DatanodeDetails datanodeDetails;
+    int firstNodeNdx = getRand().nextInt(healthyNodes.size());
+    int secondNodeNdx = getRand().nextInt(healthyNodes.size());
+
+    // There is a possibility that both numbers will be same.
+    // if that is so, we just return the node.
+    if (firstNodeNdx == secondNodeNdx) {
+      datanodeDetails = healthyNodes.get(firstNodeNdx);
+    } else {
+      DatanodeDetails firstNodeDetails = healthyNodes.get(firstNodeNdx);
+      DatanodeDetails secondNodeDetails = healthyNodes.get(secondNodeNdx);
+      datanodeDetails = nodeManager.getPipelinesCount(firstNodeDetails)
+          >= nodeManager.getPipelinesCount(secondNodeDetails)
+          ? secondNodeDetails : firstNodeDetails;
+    }
+    return datanodeDetails;
+  }
+
+  private List<DatanodeDetails> getLowerLoadNodes(
+      List<DatanodeDetails> nodes, int num) {
+    int maxPipelineUsage = nodes.size() * heavyNodeCriteria /
+        HddsProtos.ReplicationFactor.THREE.getNumber();
+    return nodes.stream()
+        // Skip the nodes which exceeds the load limit.
+        .filter(p -> nodeManager.getPipelinesCount(p) < num - maxPipelineUsage)
+        .collect(Collectors.toList());
+  }
+
+  private DatanodeDetails lowerLoadPick(List<DatanodeDetails> healthyNodes) {
+    int curPipelineCounts =  stateManager
+        .getPipelines(HddsProtos.ReplicationType.RATIS).size();
+    DatanodeDetails datanodeDetails;
+    List<DatanodeDetails> nodes = getLowerLoadNodes(
+        healthyNodes, curPipelineCounts);
+    if (nodes.isEmpty()) {
+      // random pick node if nodes load is at same level.
+      datanodeDetails = randomPick(healthyNodes);
+    } else {
+      datanodeDetails = nodes.stream().findFirst().get();
 
 Review comment:
   Sorting the node list would be expensive for large cluster. That's the reason why I choose to do this 'water mark' filter for selecting nodes with lower load. 
   
   I can def do a findAny() kinda thing for random pick.

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