Huang Kuan Hao created HDDS-16279:
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Summary: Cache replica index map in Pipeline
Key: HDDS-16279
URL: https://issues.apache.org/jira/browse/HDDS-16279
Project: Apache Ozone
Issue Type: Sub-task
Reporter: Huang Kuan Hao
Pipeline is immutable, but getReplicaIndexes() re-derives a map (list + toMap +
boxing) on every call, on the per-block-read command-build path:
public Map<DatanodeDetails, Integer> getReplicaIndexes() {
return this.getNodes().stream()
.collect(Collectors.toMap(Function.identity(), this::getReplicaIndex));
}
Fix: memoize the derived map with a lazy holder:
private volatile Map<DatanodeDetails, Integer> replicaIndexesView;
public Map<DatanodeDetails, Integer> getReplicaIndexes() {
Map<DatanodeDetails, Integer> v = replicaIndexesView;
if (v == null) {
v = getNodes().stream().collect(Collectors.toMap(Function.identity(),
this::getReplicaIndex));
replicaIndexesView = v; // benign race; Pipeline is immutable
}
return v;
}
Note: cache the derived map — it covers all nodes with a 0 default
(getReplicaIndex), unlike the internal replicaIndexes field (explicit-index
nodes only). Do not return the field. Behavior unchanged.
File: hadoop-hdds/common/.../hdds/scm/pipeline/Pipeline.java:247
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