HDFS-17605. Reduce memory overhead of TestBPOfferService

[sodonnel]

Description of PR

With default memory settings TestBPOfferService often errors with GC overhead / OOM errors. After analysing the heap dump, this is due to Mockito holding lots of references to invocations on a datanode mock.

This mock is never checked for invocations so we can mark it as stubonly and allow Mockito to drop the invocations. This small change allows the test to consistently pass on my local environment.

How was this patch tested?

This is a test only change. I ran the test several times in my fork to ensure it passed consistently when it often failed prior to the fix.

[hadoop-yetus]

💔 -1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	0m 29s		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	45m 18s		trunk passed
+1 💚	compile	1m 25s		trunk passed with JDK Ubuntu-11.0.24+8-post-Ubuntu-1ubuntu320.04
+1 💚	compile	1m 20s		trunk passed with JDK Private Build-1.8.0_422-8u422-b05-1~20.04-b05
+1 💚	checkstyle	1m 11s		trunk passed
+1 💚	mvnsite	1m 27s		trunk passed
+1 💚	javadoc	1m 11s		trunk passed with JDK Ubuntu-11.0.24+8-post-Ubuntu-1ubuntu320.04
+1 💚	javadoc	1m 40s		trunk passed with JDK Private Build-1.8.0_422-8u422-b05-1~20.04-b05
+1 💚	spotbugs	3m 35s		trunk passed
+1 💚	shadedclient	38m 27s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	1m 15s		the patch passed
+1 💚	compile	1m 18s		the patch passed with JDK Ubuntu-11.0.24+8-post-Ubuntu-1ubuntu320.04
+1 💚	javac	1m 18s		the patch passed
+1 💚	compile	1m 10s		the patch passed with JDK Private Build-1.8.0_422-8u422-b05-1~20.04-b05
+1 💚	javac	1m 10s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	checkstyle	0m 58s		the patch passed
+1 💚	mvnsite	1m 12s		the patch passed
+1 💚	javadoc	0m 54s		the patch passed with JDK Ubuntu-11.0.24+8-post-Ubuntu-1ubuntu320.04
+1 💚	javadoc	1m 33s		the patch passed with JDK Private Build-1.8.0_422-8u422-b05-1~20.04-b05
+1 💚	spotbugs	3m 23s		the patch passed
+1 💚	shadedclient	39m 33s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
-1 ❌	unit	234m 9s	/patch-unit-hadoop-hdfs-project_hadoop-hdfs.txt	hadoop-hdfs in the patch passed.
+1 💚	asflicense	0m 48s		The patch does not generate ASF License warnings.
		380m 0s

Reason	Tests
Failed junit tests	hadoop.hdfs.TestReconstructStripedFileWithRandomECPolicy
	hadoop.hdfs.TestErasureCodingPolicies
	hadoop.hdfs.TestDecommissionWithStriped
	hadoop.hdfs.TestDFSStripedOutputStreamWithFailureWithRandomECPolicy

Subsystem	Report/Notes
Docker	ClientAPI=1.44 ServerAPI=1.44 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-6996/1/artifact/out/Dockerfile
GITHUB PR	#6996
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell detsecrets
uname	Linux 744b31aeaa82 5.15.0-94-generic #104-Ubuntu SMP Tue Jan 9 15:25:40 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / 9114fed
Default Java	Private Build-1.8.0_422-8u422-b05-1~20.04-b05
Multi-JDK versions	/usr/lib/jvm/java-11-openjdk-amd64:Ubuntu-11.0.24+8-post-Ubuntu-1ubuntu320.04 /usr/lib/jvm/java-8-openjdk-amd64:Private Build-1.8.0_422-8u422-b05-1~20.04-b05
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-6996/1/testReport/
Max. process+thread count	3553 (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-6996/1/console
versions	git=2.25.1 maven=3.6.3 spotbugs=4.2.2
Powered by	Apache Yetus 0.14.0 https://yetus.apache.org

This message was automatically generated.

[sodonnel]

Test failures are unrelated. @umamaheswararao could you give this a review if you get a minute? Its a one line change in a test file only. Thanks!

[slfan1989]

LGTM. This modification is reasonable.

[sodonnel]

Thanks for the review @slfan1989