aajisaka commented on a change in pull request #3148:
URL: https://github.com/apache/hadoop/pull/3148#discussion_r660477088
##########
File path:
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java
##########
@@ -340,8 +343,7 @@ public static InetSocketAddress createSocketAddr(String
target) {
private DataNodePeerMetrics peerMetrics;
private DataNodeDiskMetrics diskMetrics;
private InetSocketAddress streamingAddr;
-
- // See the note below in incrDatanodeNetworkErrors re: concurrency.
+
private LoadingCache<String, Map<String, Long>> datanodeNetworkCounts;
Review comment:
I think `HashMap<String, LongAdder>` is more efficient than
`ConcurrentHashMap<String, Long>` because the LongAdder instance in the Map is
never replaced in this case.
##########
File path:
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java
##########
@@ -340,8 +343,7 @@ public static InetSocketAddress createSocketAddr(String
target) {
private DataNodePeerMetrics peerMetrics;
private DataNodeDiskMetrics diskMetrics;
private InetSocketAddress streamingAddr;
-
- // See the note below in incrDatanodeNetworkErrors re: concurrency.
+
private LoadingCache<String, Map<String, Long>> datanodeNetworkCounts;
Review comment:
Oh I found the interface
```
@Override // DataNodeMXBean
public Map<String, Map<String, Long>> getDatanodeNetworkCounts() {
return datanodeNetworkCounts.asMap();
}
```
Since the interface cannot be changed, it's okay to use ConcurrentHashMap.
+1.
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