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https://issues.apache.org/jira/browse/HADOOP-19447?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17925789#comment-17925789
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Tao Yang commented on HADOOP-19447:
-----------------------------------
Thanks [~yangjiandan] for introducing this improvement, it's very useful for
large-scale clusters.
> 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
>
> *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 & CachedResolver{*}:
> •Modify HostResolver to use HostnameCache for hostname lookups.
> •Update NodesListManager.CachedResolver to use HostnameCache instead of its
> own internal cache.
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