YARN-11992. Preserve reservation result and node during multi-node allocation

[luoyuan3471]

Description of PR

Multi-node allocation can reserve a container on an earlier candidate, then overwrite the allocation result when a later node is skipped during the node precheck. When candidate traversal ends, the earlier reservation is discarded or may be completed against the wrong node.

This change tracks the latest reservation together with the node that produced it, completes that reservation after later node-level skips, and returns successful allocations directly so they cannot fall back to a stale reservation.

JIRA: https://issues.apache.org/jira/browse/YARN-11992

How was this patch tested?

• Added focused regression coverage in TestRegularContainerAllocator for preserving an earlier reservation after a later candidate is skipped, completing the reservation on its original node, and avoiding fallback to a stale reservation when doAllocation does not allocate.
• TestRegularContainerAllocator: 3 tests passed.
• TestCapacitySchedulerMultiNodes: 8 tests passed;

[luoyuan3471]

Hi @slfan1989, could you please take a look when you have time? This fixes a multi-node reservation issue in RegularContainerAllocator, where a later skipped candidate can overwrite an earlier reservation result or cause it to be completed against the wrong node. The change is closely related to the candidate precheck flow updated in YARN-11798 (#7516), and includes focused regression tests. Thanks!

[hadoop-yetus]

🎊 +1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	14m 33s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 0s		No case conflicting files found.
+0 🆗	codespell	0m 1s		codespell was not available.
+0 🆗	detsecrets	0m 1s		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	99m 22s		trunk passed
+1 💚	compile	1m 27s		trunk passed with JDK Ubuntu-21.0.12.1+1-1-24.04.4-Ubuntu
+1 💚	compile	1m 31s		trunk passed with JDK Ubuntu-17.0.20.1+1-1-24.04-Ubuntu
+1 💚	checkstyle	1m 29s		trunk passed
+1 💚	mvnsite	1m 34s		trunk passed
+1 💚	javadoc	1m 22s		trunk passed with JDK Ubuntu-21.0.12.1+1-1-24.04.4-Ubuntu
+1 💚	javadoc	1m 17s		trunk passed with JDK Ubuntu-17.0.20.1+1-1-24.04-Ubuntu
+1 💚	spotbugs	2m 42s		trunk passed
+1 💚	shadedclient	30m 48s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	1m 2s		the patch passed
+1 💚	compile	0m 57s		the patch passed with JDK Ubuntu-21.0.12.1+1-1-24.04.4-Ubuntu
+1 💚	javac	0m 57s		the patch passed
+1 💚	compile	0m 59s		the patch passed with JDK Ubuntu-17.0.20.1+1-1-24.04-Ubuntu
+1 💚	javac	0m 59s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	checkstyle	0m 51s		the patch passed
+1 💚	mvnsite	1m 2s		the patch passed
+1 💚	javadoc	0m 48s		the patch passed with JDK Ubuntu-21.0.12.1+1-1-24.04.4-Ubuntu
+1 💚	javadoc	0m 47s		the patch passed with JDK Ubuntu-17.0.20.1+1-1-24.04-Ubuntu
+1 💚	spotbugs	2m 17s		the patch passed
+1 💚	shadedclient	29m 37s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
+1 💚	unit	116m 12s		hadoop-yarn-server-resourcemanager in the patch passed.
+1 💚	asflicense	0m 40s		The patch does not generate ASF License warnings.
		311m 45s

Subsystem	Report/Notes
Docker	ClientAPI=1.56 ServerAPI=1.56 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-8752/7/artifact/out/Dockerfile
GITHUB PR	#8752
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell detsecrets
uname	Linux ec7379c77dab 5.15.0-186-generic #196-Ubuntu SMP Sat Jun 20 16:09:34 UTC 2026 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / 8765ce2
Default Java	Ubuntu-17.0.20.1+1-1-24.04-Ubuntu
Multi-JDK versions	/usr/lib/jvm/java-21-openjdk-amd64:Ubuntu-21.0.12.1+1-1-24.04.4-Ubuntu /usr/lib/jvm/java-17-openjdk-amd64:Ubuntu-17.0.20.1+1-1-24.04-Ubuntu
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-8752/7/testReport/
Max. process+thread count	969 (vs. ulimit of 10000)
modules	C: hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager U: hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-8752/7/console
versions	git=2.43.0 maven=3.9.15 spotbugs=4.9.7
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