HDFS-13522. RBF: Support observer node from Router-Based Federation

[zhengzhuobinzzb]

NOTICE

Please create an issue in ASF JIRA before opening a pull request,
and you need to set the title of the pull request which starts with
the corresponding JIRA issue number. (e.g. HADOOP-XXXXX. Fix a typo in YYY.)
For more details, please see https://cwiki.apache.org/confluence/display/HADOOP/How+To+Contribute

[hadoop-yetus]

💔 -1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	19m 48s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 0s		No case conflicting files found.
+0 🆗	codespell	0m 1s		codespell was not available.
+1 💚	@author	0m 0s		The patch does not contain any @author tags.
+1 💚	test4tests	0m 0s		The patch appears to include 11 new or modified test files.
			_ trunk Compile Tests _
+0 🆗	mvndep	12m 46s		Maven dependency ordering for branch
+1 💚	mvninstall	20m 12s		trunk passed
+1 💚	compile	20m 56s		trunk passed with JDK Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04
+1 💚	compile	18m 11s		trunk passed with JDK Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
+1 💚	checkstyle	3m 51s		trunk passed
+1 💚	mvnsite	5m 24s		trunk passed
+1 💚	javadoc	4m 13s		trunk passed with JDK Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04
+1 💚	javadoc	5m 35s		trunk passed with JDK Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
+1 💚	spotbugs	9m 55s		trunk passed
+1 💚	shadedclient	14m 57s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+0 🆗	mvndep	0m 27s		Maven dependency ordering for patch
+1 💚	mvninstall	3m 30s		the patch passed
+1 💚	compile	20m 18s		the patch passed with JDK Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04
+1 💚	javac	20m 18s		the patch passed
+1 💚	compile	18m 14s		the patch passed with JDK Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
+1 💚	javac	18m 14s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
-0 ⚠️	checkstyle	3m 42s	/results-checkstyle-root.txt	root: The patch generated 5 new + 439 unchanged - 1 fixed = 444 total (was 440)
+1 💚	mvnsite	5m 21s		the patch passed
+1 💚	xml	0m 3s		The patch has no ill-formed XML file.
+1 💚	javadoc	4m 10s		the patch passed with JDK Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04
+1 💚	javadoc	5m 32s		the patch passed with JDK Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
+1 💚	spotbugs	10m 35s		the patch passed
+1 💚	shadedclient	15m 2s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
+1 💚	unit	17m 2s		hadoop-common in the patch passed.
+1 💚	unit	2m 39s		hadoop-hdfs-client in the patch passed.
-1 ❌	unit	399m 9s	/patch-unit-hadoop-hdfs-project_hadoop-hdfs.txt	hadoop-hdfs in the patch passed.
+1 💚	unit	30m 43s		hadoop-hdfs-rbf in the patch passed.
+1 💚	asflicense	1m 6s		The patch does not generate ASF License warnings.
		677m 17s

Reason	Tests
Failed junit tests	hadoop.fs.viewfs.TestViewFSOverloadSchemeWithMountTableConfigInHDFS
	hadoop.hdfs.web.TestWebHdfsFileSystemContract
	hadoop.hdfs.server.namenode.TestDecommissioningStatusWithBackoffMonitor
	hadoop.hdfs.TestDFSShell
	hadoop.hdfs.server.namenode.ha.TestBootstrapStandby
	hadoop.hdfs.server.namenode.ha.TestEditLogTailer
	hadoop.fs.viewfs.TestViewFileSystemOverloadSchemeWithHdfsScheme
	hadoop.hdfs.server.namenode.TestDecommissioningStatus
	hadoop.fs.viewfs.TestViewFileSystemOverloadSchemeHdfsFileSystemContract

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-3005/15/artifact/out/Dockerfile
GITHUB PR	#3005
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell xml
uname	Linux 7f5f496a038f 4.15.0-112-generic #113-Ubuntu SMP Thu Jul 9 23:41:39 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / 49b86f1
Default Java	Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
Multi-JDK versions	/usr/lib/jvm/java-11-openjdk-amd64:Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04 /usr/lib/jvm/java-8-openjdk-amd64:Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-3005/15/testReport/
Max. process+thread count	3289 (vs. ulimit of 5500)
modules	C: hadoop-common-project/hadoop-common hadoop-hdfs-project/hadoop-hdfs-client hadoop-hdfs-project/hadoop-hdfs hadoop-hdfs-project/hadoop-hdfs-rbf U: .
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-3005/15/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.

[sunchao]

@zhengzhuobinzzb to help reviewing, could you describe the approach you're taking in this PR in the description? cc @fengnanli too.

[zhengzhuobinzzb]

@zhengzhuobinzzb to help reviewing, could you describe the approach you're taking in this PR in the description? cc @fengnanli too.

Hi, @sunchao . Thanks for review!
Describe in this doc: https://docs.google.com/document/d/1rPZK2GyaivSNpNPkZknMLil9ZfIGr439yUf8TLhTFJM/edit#