[jira] [Commented] (HADOOP-19447) Add Caching Mechanism to HostResolver to Avoid Redundant Hostname Resolutions

["ASF GitHub Bot (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-19447?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17939853#comment-17939853 ] 

ASF GitHub Bot commented on HADOOP-19447:
-----------------------------------------

slfan1989 commented on code in PR #7527:
URL: https://github.com/apache/hadoop/pull/7527#discussion_r2021996002


##########
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/SecurityUtil.java:
##########
@@ -586,17 +594,62 @@ InetAddress getByName(String hostname) throws UnknownHostException {
       return hostResolver.getByName(hostname);
     }
   }
-  
+
   interface HostResolver {
-    InetAddress getByName(String host) throws UnknownHostException;    
+    InetAddress getByName(String host) throws UnknownHostException;
+  }
+
+  static abstract class CacheableHostResolver implements HostResolver {
+    private volatile LoadingCache<String, InetAddress> cache;
+
+    CacheableHostResolver(long expiryIntervalSecs) {
+      if (expiryIntervalSecs > 0) {
+        cache = CacheBuilder.newBuilder()
+            .expireAfterWrite(expiryIntervalSecs, TimeUnit.SECONDS)

Review Comment:
   Thanks for the explanation! this makes sense to me.





> 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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