HDFS-17878. Reduce frequency of getDatanodeListForReport calls for metrics

[kokonguyen191]

Description of PR

getDatanodeListForReport is called by a lot of metrics method while holding synchronized lock, interfering with more critical ops like datanodeReport while not having critical data (metrics). Best to reduce the frequency of calls to this method. This patch added a configurable cache that is force-wiped when there is a change in DNs, else expires using the configured expiration period.

How was this patch tested?

Product cluster + local UT benchmark

[hadoop-yetus]

💔 -1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	1m 49s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 1s		No case conflicting files found.
+0 🆗	codespell	0m 0s		codespell was not available.
+0 🆗	detsecrets	0m 0s		detect-secrets was not available.
+0 🆗	xmllint	0m 0s		xmllint was not available.
+1 💚	@author	0m 0s		The patch does not contain any @author tags.
+1 💚	test4tests	0m 0s		The patch appears to include 9 new or modified test files.
			_ trunk Compile Tests _
+1 💚	mvninstall	42m 3s		trunk passed
+1 💚	compile	1m 44s		trunk passed with JDK Ubuntu-21.0.7+6-Ubuntu-0ubuntu120.04
+1 💚	compile	1m 45s		trunk passed with JDK Ubuntu-17.0.15+6-Ubuntu-0ubuntu120.04
+1 💚	checkstyle	1m 17s		trunk passed
+1 💚	mvnsite	1m 54s		trunk passed
+1 💚	javadoc	1m 32s		trunk passed with JDK Ubuntu-21.0.7+6-Ubuntu-0ubuntu120.04
+1 💚	javadoc	1m 30s		trunk passed with JDK Ubuntu-17.0.15+6-Ubuntu-0ubuntu120.04
+1 💚	spotbugs	4m 7s		trunk passed
+1 💚	shadedclient	30m 41s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	1m 20s		the patch passed
+1 💚	compile	1m 15s		the patch passed with JDK Ubuntu-21.0.7+6-Ubuntu-0ubuntu120.04
+1 💚	javac	1m 15s		the patch passed
+1 💚	compile	1m 17s		the patch passed with JDK Ubuntu-17.0.15+6-Ubuntu-0ubuntu120.04
+1 💚	javac	1m 17s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
-0 ⚠️	checkstyle	0m 47s	/results-checkstyle-hadoop-hdfs-project_hadoop-hdfs.txt	hadoop-hdfs-project/hadoop-hdfs: The patch generated 3 new + 518 unchanged - 6 fixed = 521 total (was 524)
+1 💚	mvnsite	1m 22s		the patch passed
-1 ❌	javadoc	0m 58s	/results-javadoc-javadoc-hadoop-hdfs-project_hadoop-hdfs-jdkUbuntu-21.0.7+6-Ubuntu-0ubuntu120.04.txt	hadoop-hdfs-project_hadoop-hdfs-jdkUbuntu-21.0.7+6-Ubuntu-0ubuntu120.04 with JDK Ubuntu-21.0.7+6-Ubuntu-0ubuntu120.04 generated 6 new + 9994 unchanged - 6 fixed = 10000 total (was 10000)
-1 ❌	javadoc	0m 58s	/results-javadoc-javadoc-hadoop-hdfs-project_hadoop-hdfs-jdkUbuntu-17.0.15+6-Ubuntu-0ubuntu120.04.txt	hadoop-hdfs-project_hadoop-hdfs-jdkUbuntu-17.0.15+6-Ubuntu-0ubuntu120.04 with JDK Ubuntu-17.0.15+6-Ubuntu-0ubuntu120.04 generated 6 new + 9676 unchanged - 0 fixed = 9682 total (was 9676)
+1 💚	spotbugs	3m 45s		the patch passed
+1 💚	shadedclient	29m 38s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
-1 ❌	unit	268m 39s	/patch-unit-hadoop-hdfs-project_hadoop-hdfs.txt	hadoop-hdfs in the patch passed.
+1 💚	asflicense	0m 45s		The patch does not generate ASF License warnings.
		408m 3s

Reason	Tests
Failed junit tests	hadoop.hdfs.tools.TestDFSAdmin

Subsystem	Report/Notes
Docker	ClientAPI=1.53 ServerAPI=1.53 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-8220/1/artifact/out/Dockerfile
GITHUB PR	#8220
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell detsecrets xmllint
uname	Linux cb95265244c7 5.15.0-164-generic #174-Ubuntu SMP Fri Nov 14 20:25:16 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / 8dd731f
Default Java	Ubuntu-17.0.15+6-Ubuntu-0ubuntu120.04
Multi-JDK versions	/usr/lib/jvm/java-21-openjdk-amd64:Ubuntu-21.0.7+6-Ubuntu-0ubuntu120.04 /usr/lib/jvm/java-17-openjdk-amd64:Ubuntu-17.0.15+6-Ubuntu-0ubuntu120.04
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-8220/1/testReport/
Max. process+thread count	3249 (vs. ulimit of 5500)
modules	C: hadoop-hdfs-project/hadoop-hdfs U: hadoop-hdfs-project/hadoop-hdfs
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-8220/1/console
versions	git=2.25.1 maven=3.9.11 spotbugs=4.9.7
Powered by	Apache Yetus 0.14.1 https://yetus.apache.org

This message was automatically generated.