sodonnel 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_r396774317
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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:
You could probably do a "top N" type of sort where you only keep the lowest
loaded node, but it would require a bit of a refactor of `getLowerLoadNodes`,
probably changing it to `getLowestLodeNode`. That would avoid a full sort and
would not be much more expensive that the current code, eg:
```
DatanodeDetails lowest = null;
int lowestPipelineCount;
for (DatanodeDetails dn : nodes) {
int nodePipelines = node.getPipelineCount();
if (nodePipelines > limit) {
continue;
}
if ((lowest == null) || lowestPipelineCount > nodePipelines {
lowest = node;
lowestPipelineCount = nodePipelines;
}
}
return lowest;
```
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