HBASE-25841 Add basic jshell support #3224

ndimiduk · 2021-05-03T19:29:21Z

No description provided.

ndimiduk · 2021-05-03T19:30:49Z

Doesn't do anything other than adding a jshell command to the shell script entry point. Perhaps we also want to provide a startup script that will automatically import some set of packages/classes?

ndimiduk · 2021-05-03T19:33:13Z

$ JAVA_HOME=/Library/Java/JavaVirtualMachines/adoptopenjdk-8.jdk/Contents/Home ./bin/hbase jshell
JShell is available only with JDK9 and lated. Detected JDK version is 1.8.0_282-b08.

$ JAVA_HOME=/Library/Java/JavaVirtualMachines/adoptopenjdk-11.jdk/Contents/Home ./bin/hbase jshell
|  Welcome to JShell -- Version 11.0.10
|  For an introduction type: /help intro

jshell> import org.apache.hadoop.hbase.HConstants

jshell> HConstants.MASTER_PORT
$2 ==> "hbase.master.port"

jshell>

Apache9 · 2021-05-04T00:56:14Z

Could you please provide some examples on how to make use of this jshell? It is just a standalone process? Not inside a master or regionserver process?

ndimiduk · 2021-05-04T16:10:40Z

Could you please provide some examples on how to make use of this jshell? It is just a standalone process? Not inside a master or regionserver process?

Sure. I see this being as a more advanced feature, maybe a developer feature. I'm not really sure who the intended audience of the jshell is from JDK perspective...

The patch as I've posted provides an interactive environment with HBase classes loaded. It is the equivalent of a Ruby IRB session, without all of the helpful DSL code we have that makes the hbase shell experience. Unlike that IRB, this is a Java language experience, not a Ruby language experience.

This is a stand-alone process that is run by a user on-demand. It does not impact any of our existing daemon processes.

Here's an example of how we might update our examples in the book from being code snippets to being jshell snippets,

$ ./bin/hbase jshell
|  Welcome to JShell -- Version 11.0.10
|  For an introduction type: /help intro

jshell> import org.apache.hadoop.hbase.client.*;

jshell> ConnectionFactory.createAsyncConnection()
   ...>       .thenApply(AsyncConnection::getAdmin)
   ...>       .thenCompose(AsyncAdmin::getMaster)
   ...>       .get()
2021-05-04T09:00:17,827 WARN  [main] util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
$2 ==> localhost,16000,1620143354294

bharathv

I think this is useful for quickly debugging class path issues and such (or even small programs) saving the time taken to compile test classes. Handy to have the entire class path loaded into the jvm.

apurtell · 2021-05-10T17:12:58Z

Perhaps we also want to provide a startup script that will automatically import some set of packages/classes?

Yes, it wouldn't be a useful experience otherwise, and so this would save everyone some typing at every start time.

madrob · 2021-05-11T14:51:54Z

Agree that we should specify a startup script with base imports, make sure you include the default imports too though because --startup flag overwrites the default script, not appends.

ndimiduk · 2021-05-13T23:29:28Z

I think I've addresses everyone's concerns. Please give it a spin and let me know if there are other imports we should include by default (for example, I initially considered org.apache.hadoop.conf.Configuration).

I'm still looking into whether we can override the welcome message or add a new entry to the /help command. But I don't think those are critical changes, and I'd be happy to commit this with the features already present.

ndimiduk · 2021-05-13T23:38:23Z

Also, HBASE-25889.

Apache-HBase · 2021-05-13T23:38:48Z

🎊 +1 overall

Vote	Subsystem	Runtime	Comment
+0 🆗	reexec	1m 1s	Docker mode activated.
-0 ⚠️	yetus	0m 2s	Unprocessed flag(s): --brief-report-file --spotbugs-strict-precheck --whitespace-eol-ignore-list --whitespace-tabs-ignore-list --quick-hadoopcheck
		_ Prechecks _
		_ master Compile Tests _
		_ Patch Compile Tests _
		_ Other Tests _
		2m 9s

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/HBase/job/HBase-PreCommit-GitHub-PR/job/PR-3224/2/artifact/yetus-jdk11-hadoop3-check/output/Dockerfile
GITHUB PR	#3224
Optional Tests
uname	Linux fd5e85931748 4.15.0-142-generic #146-Ubuntu SMP Tue Apr 13 01:11:19 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
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git revision	master / `b65733c`
Max. process+thread count	50 (vs. ulimit of 30000)
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