HDFS-16530. setReplication debug log creates a new string even if debug is disabled

[sodonnel]

Description of PR

In FSDirAttrOp, HDFS-14521 made a good change to move a noisy logger to debug:

      if (oldBR > targetReplication) {
        FSDirectory.LOG.debug("Decreasing replication from {} to {} for {}",
                             oldBR, targetReplication, iip.getPath());
      } else if (oldBR < targetReplication) {
        FSDirectory.LOG.debug("Increasing replication from {} to {} for {}",
                             oldBR, targetReplication, iip.getPath());
      } else {
        FSDirectory.LOG.debug("Replication remains unchanged at {} for {}",
                             oldBR, iip.getPath());
      }
    }

However the iip.getPath() method must be evaluated to pass the resulting string into the LOG.debug method, even if debug is not enabled:

This code may form a new string where it does not need to:

  public String getPath() {
    if (pathname == null) {
      pathname = DFSUtil.byteArray2PathString(path);
    }
    return pathname;
  }

We should wrap the entire logging block in if LOG.debugEnabled() to avoid any overhead when the logger is not enabled.

How was this patch tested?

No new tests - simple change.

[aajisaka]

Nice catch @sodonnel. +1 pending Jenkins.

[hadoop-yetus]

💔 -1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	1m 1s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 1s		No case conflicting files found.
+0 🆗	codespell	0m 0s		codespell was not available.
+1 💚	@author	0m 0s		The patch does not contain any @author tags.
-1 ❌	test4tests	0m 0s		The patch doesn't appear to include any new or modified tests. Please justify why no new tests are needed for this patch. Also please list what manual steps were performed to verify this patch.
			_ trunk Compile Tests _
+1 💚	mvninstall	38m 48s		trunk passed
+1 💚	compile	1m 28s		trunk passed with JDK Ubuntu-11.0.14+9-Ubuntu-0ubuntu2.20.04
+1 💚	compile	1m 23s		trunk passed with JDK Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
+1 💚	checkstyle	1m 7s		trunk passed
+1 💚	mvnsite	1m 30s		trunk passed
+1 💚	javadoc	1m 8s		trunk passed with JDK Ubuntu-11.0.14+9-Ubuntu-0ubuntu2.20.04
+1 💚	javadoc	1m 33s		trunk passed with JDK Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
+1 💚	spotbugs	3m 33s		trunk passed
+1 💚	shadedclient	23m 17s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	1m 15s		the patch passed
+1 💚	compile	1m 22s		the patch passed with JDK Ubuntu-11.0.14+9-Ubuntu-0ubuntu2.20.04
+1 💚	javac	1m 22s		the patch passed
+1 💚	compile	1m 17s		the patch passed with JDK Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
+1 💚	javac	1m 17s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	checkstyle	0m 51s		the patch passed
+1 💚	mvnsite	1m 16s		the patch passed
+1 💚	javadoc	0m 52s		the patch passed with JDK Ubuntu-11.0.14+9-Ubuntu-0ubuntu2.20.04
+1 💚	javadoc	1m 23s		the patch passed with JDK Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
+1 💚	spotbugs	3m 15s		the patch passed
+1 💚	shadedclient	22m 26s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
-1 ❌	unit	411m 2s	/patch-unit-hadoop-hdfs-project_hadoop-hdfs.txt	hadoop-hdfs in the patch passed.
+1 💚	asflicense	0m 49s		The patch does not generate ASF License warnings.
		518m 14s

Reason	Tests
Failed junit tests	hadoop.hdfs.server.namenode.ha.TestSeveralNameNodes

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-4142/1/artifact/out/Dockerfile
GITHUB PR	#4142
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell
uname	Linux 271839763d3f 4.15.0-65-generic #74-Ubuntu SMP Tue Sep 17 17:06:04 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / 90fe079
Default Java	Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
Multi-JDK versions	/usr/lib/jvm/java-11-openjdk-amd64:Ubuntu-11.0.14+9-Ubuntu-0ubuntu2.20.04 /usr/lib/jvm/java-8-openjdk-amd64:Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-4142/1/testReport/
Max. process+thread count	2608 (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-4142/1/console
versions	git=2.25.1 maven=3.6.3 spotbugs=4.2.2
Powered by	Apache Yetus 0.14.0-SNAPSHOT https://yetus.apache.org

This message was automatically generated.

[sodonnel]

TestSeveralNamenodes passes locally and couldn't be related to this, so I will go ahead and commit this one. Thanks for the review @aajisaka