HDFS-17970. Exclude failed EC checksum target from reconstruction sources

[zouhuajian]

Description of PR

This PR fixes HDFS-17970.

During striped block checksum reconstruction, the DataNode that failed the original checksum request could still be selected as a reconstruction source. This may cause reconstruction to read from the same failed target and prevent the file checksum from being calculated.

This change:

• excludes every location belonging to the failed checksum target from the reconstruction source candidates;
• keeps source block indices aligned with their corresponding DataNode locations during source selection;
• preserves valid non-target replicas when selecting the required sources;
• adds a deterministic regression test that triggers the checksum reconstruction fallback with an invalid child block token.

Contains content generated by OpenAI Codex.

How was this patch tested?

• Ran the focused regression test: TestFileChecksum#testStripedFileChecksumReconstructionExcludesFailedTarget (2 tests passed).
• Ran the complete TestFileChecksum test class (72 tests passed).
• Ran git diff --check.

For code changes:

• Does the title of this PR start with the corresponding JIRA issue id (e.g. 'HADOOP-17799. Your PR title ...')?
• Object storage: Have the integration tests been executed and the endpoint declared according to the connector-specific documentation? Note: Automated CI testing doesn't cover all cases so manual testing with cloud storage is still required.
• If adding new dependencies to the code, are these dependencies licensed in a way that is compatible for inclusion under ASF 2.0?
• If applicable, have you updated the LICENSE, LICENSE-binary, NOTICE-binary files?

The unchecked object storage, dependency, and license-file items are not applicable to this change.

AI Tooling

If an AI tool was used:

• The PR includes the phrase "Contains content generated by OpenAI Codex."
• My use of AI contributions follows the ASF legal policy https://www.apache.org/legal/generative-tooling.html

[hadoop-yetus]

💔 -1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	19m 46s		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 _
+1 💚	mvninstall	47m 54s		trunk passed
+1 💚	compile	1m 50s		trunk passed with JDK Ubuntu-21.0.12+8-1-24.04-Ubuntu
+1 💚	compile	1m 49s		trunk passed with JDK Ubuntu-17.0.20+8-1-24.04-Ubuntu
+1 💚	checkstyle	1m 50s		trunk passed
+1 💚	mvnsite	1m 59s		trunk passed
+1 💚	javadoc	1m 30s		trunk passed with JDK Ubuntu-21.0.12+8-1-24.04-Ubuntu
+1 💚	javadoc	1m 30s		trunk passed with JDK Ubuntu-17.0.20+8-1-24.04-Ubuntu
+1 💚	spotbugs	4m 23s		trunk passed
+1 💚	shadedclient	42m 50s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	1m 24s		the patch passed
+1 💚	compile	1m 17s		the patch passed with JDK Ubuntu-21.0.12+8-1-24.04-Ubuntu
+1 💚	javac	1m 17s		the patch passed
+1 💚	compile	1m 22s		the patch passed with JDK Ubuntu-17.0.20+8-1-24.04-Ubuntu
+1 💚	javac	1m 22s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	checkstyle	1m 17s		the patch passed
+1 💚	mvnsite	1m 32s		the patch passed
+1 💚	javadoc	0m 59s		the patch passed with JDK Ubuntu-21.0.12+8-1-24.04-Ubuntu
+1 💚	javadoc	1m 3s		the patch passed with JDK Ubuntu-17.0.20+8-1-24.04-Ubuntu
+1 💚	spotbugs	4m 5s		the patch passed
+1 💚	shadedclient	36m 36s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
+1 💚	unit	264m 21s		hadoop-hdfs in the patch passed.
-1 ❌	asflicense	0m 55s	/results-asflicense.txt	The patch generated 1 ASF License warnings.
		438m 6s

Subsystem	Report/Notes
Docker	ClientAPI=1.55 ServerAPI=1.55 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-8709/1/artifact/out/Dockerfile
GITHUB PR	#8709
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell detsecrets
uname	Linux ae8fd63dc7b3 5.15.0-185-generic #195-Ubuntu SMP Fri Jun 19 17:11:50 UTC 2026 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / 2339461
Default Java	Ubuntu-17.0.20+8-1-24.04-Ubuntu
Multi-JDK versions	/usr/lib/jvm/java-21-openjdk-amd64:Ubuntu-21.0.12+8-1-24.04-Ubuntu /usr/lib/jvm/java-17-openjdk-amd64:Ubuntu-17.0.20+8-1-24.04-Ubuntu
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-8709/1/testReport/
Max. process+thread count	2468 (vs. ulimit of 10000)
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-8709/1/console
versions	git=2.43.0 maven=3.9.15 spotbugs=4.9.7
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