HDFS-17632. RBF: Support listOpenFiles for routers

[kokonguyen191]

Description of PR

(reopened due to ticket being auto closed)

Routers don't have support for listOpenFiles yet. Single destination paths are straightforward. Multi destination paths are joined; entries with inodeId > min(max(entry inodeIds)) are ignored to get a consistent prevId for the iterator.

The implementation is the same as the logic used for aligning results from multiple destinations in router getListing.

How was this patch tested?

UTs

[hadoop-yetus]

💔 -1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	8m 7s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 0s		No case conflicting files found.
+0 🆗	codespell	0m 0s		codespell was not available.
+0 🆗	detsecrets	0m 0s		detect-secrets was not available.
+1 💚	@author	0m 0s		The patch does not contain any @author tags.
+1 💚	test4tests	0m 0s		The patch appears to include 1 new or modified test files.
			_ trunk Compile Tests _
+0 🆗	mvndep	6m 59s		Maven dependency ordering for branch
+1 💚	mvninstall	15m 43s		trunk passed
+1 💚	compile	3m 5s		trunk passed with JDK Ubuntu-21.0.7+6-Ubuntu-0ubuntu120.04
+1 💚	compile	3m 11s		trunk passed with JDK Ubuntu-17.0.15+6-Ubuntu-0ubuntu120.04
+1 💚	checkstyle	0m 33s		trunk passed
+1 💚	mvnsite	1m 26s		trunk passed
+1 💚	javadoc	1m 3s		trunk passed with JDK Ubuntu-21.0.7+6-Ubuntu-0ubuntu120.04
+1 💚	javadoc	1m 1s		trunk passed with JDK Ubuntu-17.0.15+6-Ubuntu-0ubuntu120.04
-1 ❌	spotbugs	1m 58s	/branch-spotbugs-hadoop-hdfs-project_hadoop-hdfs-warnings.html	hadoop-hdfs-project/hadoop-hdfs in trunk has 291 extant spotbugs warnings.
-1 ❌	spotbugs	1m 0s	/branch-spotbugs-hadoop-hdfs-project_hadoop-hdfs-rbf-warnings.html	hadoop-hdfs-project/hadoop-hdfs-rbf in trunk has 192 extant spotbugs warnings.
+1 💚	shadedclient	14m 34s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+0 🆗	mvndep	0m 16s		Maven dependency ordering for patch
+1 💚	mvninstall	1m 16s		the patch passed
+1 💚	compile	2m 58s		the patch passed with JDK Ubuntu-21.0.7+6-Ubuntu-0ubuntu120.04
+1 💚	javac	2m 58s		the patch passed
+1 💚	compile	3m 12s		the patch passed with JDK Ubuntu-17.0.15+6-Ubuntu-0ubuntu120.04
+1 💚	javac	3m 12s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	checkstyle	0m 32s		hadoop-hdfs-project: The patch generated 0 new + 38 unchanged - 1 fixed = 38 total (was 39)
+1 💚	mvnsite	1m 18s		the patch passed
+1 💚	javadoc	0m 53s		the patch passed with JDK Ubuntu-21.0.7+6-Ubuntu-0ubuntu120.04
+1 💚	javadoc	0m 54s		the patch passed with JDK Ubuntu-17.0.15+6-Ubuntu-0ubuntu120.04
+1 💚	spotbugs	3m 3s		the patch passed
+1 💚	shadedclient	14m 47s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
-1 ❌	unit	172m 57s	/patch-unit-hadoop-hdfs-project_hadoop-hdfs.txt	hadoop-hdfs in the patch passed.
+1 💚	unit	35m 14s		hadoop-hdfs-rbf in the patch passed.
+1 💚	asflicense	0m 29s		The patch does not generate ASF License warnings.
		297m 48s

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

Subsystem	Report/Notes
Docker	ClientAPI=1.52 ServerAPI=1.52 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-8072/1/artifact/out/Dockerfile
GITHUB PR	#8072
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell detsecrets
uname	Linux f223f80c2115 5.15.0-156-generic #166-Ubuntu SMP Sat Aug 9 00:02:46 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / a1a738b
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-8072/1/testReport/
Max. process+thread count	4844 (vs. ulimit of 5500)
modules	C: hadoop-hdfs-project/hadoop-hdfs hadoop-hdfs-project/hadoop-hdfs-rbf U: hadoop-hdfs-project
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-8072/1/console
versions	git=2.25.1 maven=3.9.11 spotbugs=4.9.7
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