[
https://issues.apache.org/jira/browse/HDFS-17813?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18077265#comment-18077265
]
ASF GitHub Bot commented on HDFS-17813:
---------------------------------------
Hexiaoqiao commented on code in PR #8313:
URL: https://github.com/apache/hadoop/pull/8313#discussion_r3166408381
##########
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameCache.java:
##########
@@ -147,9 +147,9 @@ void initialized() {
}
/** Promote a frequently used name to the cache */
- private void promote(final K name) {
+ private void promote(final K name, final UseCount useCount) {
transientMap.remove(name);
- cache.put(name, name);
+ cache.put(name, useCount.value);
lookups += useThreshold;
}
Review Comment:
How about fix it as the following code snippet? Thus we didn't change
signature and could keep it more simple.
```
private void promote(final K name) {
UseCount useCount = transientMap.remove(name);
cache.put(name, useCount.value);
lookups += useThreshold;
}
```
> NameCache promote wrong name to cache map
> -----------------------------------------
>
> Key: HDFS-17813
> URL: https://issues.apache.org/jira/browse/HDFS-17813
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Reporter: khazhen
> Priority: Minor
> Labels: pull-request-available
>
> The NameCache class is used to cache frequently used names in namenode, it
> promotes a name used more than useThreshold to the cache, the promote logic:
> {code:java}
> K put(final K name) {
> K internal = cache.get(name);
> if (internal != null) {
> lookups++;
> return internal;
> }
> // Track the usage count only during initialization
> if (!initialized) {
> UseCount useCount = transientMap.get(name);
> if (useCount != null) {
> useCount.increment();
> if (useCount.get() >= useThreshold) {
> promote(name); // name got promoted
> }
> return useCount.value;
> }
> useCount = new UseCount(name);
> transientMap.put(name, useCount);
> }
> return null;
> } {code}
> When promoting, the cache stores the `name` parameter from put() instead of
> the existing useCount.value. This causes the returned value to change after a
> name is promoted, resulting in memory duplication.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
