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https://issues.apache.org/jira/browse/HADOOP-19447?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17937749#comment-17937749
]
ASF GitHub Bot commented on HADOOP-19447:
-----------------------------------------
slfan1989 commented on code in PR #7527:
URL: https://github.com/apache/hadoop/pull/7527#discussion_r2009324662
##########
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/ExpiringCache.java:
##########
@@ -0,0 +1,107 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.util;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Map;
+import java.util.Timer;
+import java.util.TimerTask;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * A thread-safe cache with automatic expiration and cleanup.
+ */
+public class ExpiringCache <K, V> {
Review Comment:
ExpiringCache is a generic class. Can we replace it with a utility class
such as CaffeineCache?
> Add Caching Mechanism to HostResolver to Avoid Redundant Hostname Resolutions
> -----------------------------------------------------------------------------
>
> Key: HADOOP-19447
> URL: https://issues.apache.org/jira/browse/HADOOP-19447
> Project: Hadoop Common
> Issue Type: New Feature
> Components: common, yarn
> Reporter: Jiandan Yang
> Priority: Major
> Labels: pull-request-available
>
> *Background:*
>
> Currently, the two implementations of
> org.apache.hadoop.security.SecurityUtil.HostResolver, *StandardHostResolver
> and QualifiedHostResolver* in Hadoop performs hostname resolution each time
> it is called. *Each heartbeat between the AM and RM causes the RM to invoke
> the* HostResolver#getByName {*}method once{*}. In large-scale clusters
> running numerous applications, this results in *a high frequency of redundant
> hostname resolutions.*
>
> *Proposal:*
>
> Introduce a caching mechanism in HostResolver to store resolved hostnames for
> a configurable duration. This would:
> •Reduce redundant DNS queries.
> •Improve performance for frequently used hostnames.
> •Allow configuration options for cache size and TTL (Time-to-Live).
>
> *Suggested Implementation:*
> 1.{*}Leverage Existing CachedResolver{*}:
> The NodesListManager.CachedResolver class in Hadoop already implements a
> caching mechanism for hostname resolution. Instead of introducing an entirely
> new solution, we propose *extracting the caching logic from*
> NodesListManager.CachedResolver {*}into a separate reusable utility class{*}.
> 2.{*}Create a Shared Caching Utility{*}:
> •Extract the caching logic from NodesListManager.CachedResolver.
> •Implement a new class, e.g., HostnameCache, and place it in the Hadoop
> Common module to ensure it can be used across different components.
> 3.{*}Integrate{*} HostnameCache with *HostResolver &QualifiedHostResolver*:
> •Modify HostResolver to use HostnameCache for hostname lookups.
> •Update NodesListManager.CachedResolver to use HostnameCache instead of its
> own internal cache.
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