Add tools for ContextDefinition create and cleanup #33

dlmarion · 2025-12-03T18:40:45Z

Modified ContextDefinition to implement KeywordExecutable so that the user can use accumulo create-context-definition to create the json required for the ContextDefinition file.

Added a Cleaner to call URLClassLoader.close on instances that are about to be garbage collected. The LocalCachingContextCleaner is used to register the URLClassLoader with the Cleaner and this class also keeps references to the URLClassLoaders. The list is accessed from a MXBean so that a user can use JMX to retrieve a list of files that are referenced in the local cache directory from the classloaders that have been created but not yet gc'd. This should aid users in determining which files can be removed from the local cache directory.

Modified ContextDefinition to implement KeywordExecutable so that the user can use `accumulo create-context-definition` to create the json required for the ContextDefinition file. Added a Cleaner to call `URLClassLoader.close` on instances that are about to be garbage collected. The LocalCachingContextCleaner is used to register the URLClassLoader with the Cleaner and this class also keeps references to the URLClassLoaders. The list is accessed from a MXBean so that a user can use JMX to retrieve a list of files that are referenced in the local cache directory from the classloaders that have been created but not yet gc'd. This should aid users in determining which files can be removed from the local cache directory.

...test/java/org/apache/accumulo/classloader/lcc/LocalCachingContextClassLoaderFactoryTest.java

dlmarion · 2025-12-03T18:44:22Z

...test/java/org/apache/accumulo/classloader/lcc/MiniAccumuloClusterClassLoaderFactoryTest.java

    @Override
    public void configureMiniCluster(MiniAccumuloConfigImpl cfg,
        org.apache.hadoop.conf.Configuration coreSite) {
+      cfg.removeJvmOption("-XX:+PerfDisableSharedMem");


This requires apache/accumulo#5999 to be merged. This JVM option was not allowing the test to attach to the locally running Accumulo JVM processes. Additionally, I think this is what causes jps not to report the processes.

apache/accumulo#6062 probably affects this

Working on that now.

dlmarion · 2025-12-03T18:45:09Z

pom.xml

                <banDuplicatePomDependencyVersions />
                <dependencyConvergence />
-                <banDynamicVersions />
+                <!--                <banDynamicVersions />-->


Can revert this when 2.1.5 is released and the version changed above.

What in 2.1.5 does this PR depend on that is not in 2.1.4?

Could create a reminder issue for this.

What in 2.1.5 does this PR depend on that is not in 2.1.4?

apache/accumulo#5999

Could create a reminder issue for this.

I will do that when this PR is merged.

dlmarion · 2025-12-03T18:50:26Z

This won't build successfully until apache/accumulo#5999 is merged. Tests pass locally for me.

...lassloader/src/main/java/org/apache/accumulo/classloader/lcc/LocalCachingContextCleaner.java

ctubbsii

I didn't quite understand why this needs to depend on 2.1.5-SNAPSHOT that isn't available in 2.1.4.

...sloader/src/main/resources/META-INF/services/org.apache.accumulo.start.spi.KeywordExecutable

...lassloader/src/main/java/org/apache/accumulo/classloader/lcc/LocalCachingContextCleaner.java

...src/main/java/org/apache/accumulo/classloader/lcc/LocalCachingContextClassLoaderFactory.java

modules/local-caching-classloader/README.md

keith-turner · 2025-12-04T20:15:30Z

modules/local-caching-classloader/README.md

-and unused old files within a context cache directory.
+and unused old files within a context cache directory. To aid in this task a JMX MXBean has been created to expose the
+files that are still referenced by the classloaders that are created. For an example of how to use this MXBean, please
+see the test method `MiniAccumuloClusterClassLoaderFactoryTest.getReferencedFiles`. This method attaches to the


This could be a link to the test class.

Suggested change

see the test method `MiniAccumuloClusterClassLoaderFactoryTest.getReferencedFiles`. This method attaches to the

see the test method [MiniAccumuloClusterClassLoaderFactoryTest.getReferencedFiles](src/main/test/.../MiniAccumuloClusterClassLoaderFactoryTest.java). This method attaches to the

keith-turner · 2025-12-04T20:21:14Z

pom.xml

                <banDuplicatePomDependencyVersions />
                <dependencyConvergence />
-                <banDynamicVersions />
+                <!--                <banDynamicVersions />-->


Could create a reminder issue for this.

...lassloader/src/main/java/org/apache/accumulo/classloader/lcc/LocalCachingContextCleaner.java

...test/java/org/apache/accumulo/classloader/lcc/LocalCachingContextClassLoaderFactoryTest.java

...lassloader/src/main/java/org/apache/accumulo/classloader/lcc/LocalCachingContextCleaner.java

...ssloader/src/main/java/org/apache/accumulo/classloader/lcc/definition/ContextDefinition.java

…on/accumulo-classloaders into local-classloader-tooling

dlmarion · 2026-01-15T14:15:15Z

PR updated and re-tested locally

Co-authored-by: Keith Turner <kturner@apache.org>

…on/accumulo-classloaders into local-classloader-tooling

keith-turner · 2026-01-15T17:59:50Z

modules/local-caching-classloader/README.md

 safe to delete, it is not recommended to do so for any that are still in use,
 because they can be useful for troubleshooting.

+To aid in this task a JMX MXBean has been created to expose the files that are still referenced


This offers the building blocks to create a cleanup utility and leave that as an exercise to the reader. It would probably be best (in a follow on change) to write a cleanup utility in this project that uses these building blocks, for the following reasons.

Can document and test the cleanup code in one place. If cleanup code is written, seems suboptimal for it to live in another repo or for there to be multiple implementions.

Having a working end to end impl gives confidence that these building blocks provide everything that is needed to do cleanup.

The cleanup code will need to have some awareness of the directory layout of the cache dir which is an internal implementation detail.

The clean up utility will have to get the algorithm correct in order to avoid race conditions. Seems like its important to list the dir first prior to get refs from all processes, but not completely sure. Would need to experiment and see the code to be sure.

Could make the cleanup code more robust by failing properly if no JMX seen or mismatch in dir passed in and dirs seen from jmx.

We could make the new command line utility have subcommands to support this. Something like the following.

accumulo context-classloader --help # create context definition json and print to stdout accumulo context-classloader create -i <interval> -f {files} # remove files not in use by any of the given pids accumulo context-classloader cleanup <cache dir> {pids}

We might be able to create a tool that works in one deployment scenario, but it might be hard to make it work in many of them. More information on how to make JMX client connections and server options here: https://docs.oracle.com/javase/8/docs/technotes/guides/management/agent.html.

My test is using the connection mechanism described in the example at https://docs.oracle.com/javase/8/docs/technotes/guides/management/agent.html#gdhkq. it works because I'm using mini in the tests and I know that all of the processes are on the localhost and because I remove that one system property (If that system property is set then this mechanism doesn't find the processes).

We might be able to create a tool that works in one deployment scenario, but it might be hard to make it work in many of them

Do you know if different JMX connections could require different java code? Or can the java JMX client APIs connect to any endpoint given correct config? If the user may have to write different java code for different JMX scenarios then the best we could probably do in the project is provide a good example of the java cleanup code.

Do you know if different JMX connections could require different java code?

Yes. In the test I use

List<VirtualMachineDescriptor> vmdl = VirtualMachine.list(); and VirtualMachine vm = VirtualMachine.attach(vmd); String connectorAddress = vm.getAgentProperties() .getProperty("com.sun.management.jmxremote.localConnectorAddress");

This works to find VMs that are running locally, attachs to them, and gets the connector address from them.

What I'm unsure of, is whether or not this approach would work if any of the options listed here are set on the processes. So, it's very possible that a client would need to be coded specific to how the server is configured, but I'm not 100% sure.

In the test I remove the JVM Option -XX:+PerfDisableSharedMem from the processes started by MiniAccumulo. If I don't remove this, then VirtualMachine.list() does not find the VMs (jps probably doesn't either). In that case, I would have to construct the address (service:jmx:rmi:///jndi/rmi://hostName:portNum/jmxrmi). If the server process is using security options (TLS, authentication, etc.), then more code is likely needed.

Or can the java JMX client APIs connect to any endpoint given correct config?

We would need to write, or find, a generic JMX client library that can be configured with all options. I didn't look for that specifically, but it might exist. If we can't find one, then we could write one, but I'm not sure we should do that.

If we can't find one, then we could write one, but I'm not sure we should do that.

I agree, we should not write that. If something like that is needed, then it seems like an example is the best we can do.

Issue #45 created for this.

...ssloader/src/main/java/org/apache/accumulo/classloader/lcc/definition/ContextDefinition.java

modules/local-caching-classloader/README.md

pom.xml

modules/local-caching-classloader/pom.xml

...test/java/org/apache/accumulo/classloader/lcc/MiniAccumuloClusterClassLoaderFactoryTest.java

...g-classloader/src/main/java/org/apache/accumulo/classloader/lcc/util/DeduplicationCache.java

...src/main/java/org/apache/accumulo/classloader/lcc/LocalCachingContextClassLoaderFactory.java

...test/java/org/apache/accumulo/classloader/lcc/MiniAccumuloClusterClassLoaderFactoryTest.java

* POM improvements * Use var and multi-catch in getReferencedFiles * Add newline to toJson() * Check for nulls before calling user consumer * Rename method in DeduplicationCache (values to forEach)

ctubbsii

All my suggested changes have been merged in. I am a little concerned if there are any implications to changing the DeduplicationCache instance to static, but I've thought about it and haven't been able to come up with any reason why it would be a problem.

keith-turner · 2026-01-16T00:12:42Z

What is the benefit of making the dedupe cache static?

dlmarion · 2026-01-16T00:14:21Z

What is the benefit of making the dedupe cache static?

It had to be static to be called by the static getReferencedFiles method, which is called by the JMX MXBean.

dlmarion · 2026-01-16T13:29:34Z

Test passes for me locally. Re-tested the accumulo create-context-definition command and it's working as expected. I think this is ready for merge.

dlmarion requested review from ctubbsii, ddanielr, keith-turner and kevinrr888 December 3, 2025 18:40

dlmarion self-assigned this Dec 3, 2025

dlmarion commented Dec 3, 2025

View reviewed changes

Add -Dapache.snapshots=true to MAVEN_OPTS in GH workflows

a8a059b

dlmarion mentioned this pull request Dec 4, 2025

VFSClassLoader alternative #30

Merged

Simplified code in ContextDefinition

c674f77

dlmarion commented Dec 4, 2025

View reviewed changes

...lassloader/src/main/java/org/apache/accumulo/classloader/lcc/LocalCachingContextCleaner.java Outdated Show resolved Hide resolved

dlmarion commented Dec 4, 2025

View reviewed changes

...lassloader/src/main/java/org/apache/accumulo/classloader/lcc/LocalCachingContextCleaner.java Outdated Show resolved Hide resolved

ctubbsii reviewed Dec 4, 2025

View reviewed changes

keith-turner reviewed Dec 4, 2025

View reviewed changes

...lassloader/src/main/java/org/apache/accumulo/classloader/lcc/LocalCachingContextCleaner.java Outdated Show resolved Hide resolved

...lassloader/src/main/java/org/apache/accumulo/classloader/lcc/LocalCachingContextCleaner.java Outdated Show resolved Hide resolved

keith-turner reviewed Dec 4, 2025

View reviewed changes

...lassloader/src/main/java/org/apache/accumulo/classloader/lcc/LocalCachingContextCleaner.java Outdated Show resolved Hide resolved

kevinrr888 reviewed Dec 4, 2025

View reviewed changes

...test/java/org/apache/accumulo/classloader/lcc/LocalCachingContextClassLoaderFactoryTest.java Outdated Show resolved Hide resolved

Merge branch 'main' into local-classloader-tooling

10fc626

ctubbsii reviewed Jan 13, 2026

View reviewed changes

...lassloader/src/main/java/org/apache/accumulo/classloader/lcc/LocalCachingContextCleaner.java Outdated Show resolved Hide resolved

dlmarion added 2 commits January 14, 2026 23:16

Merge branch 'main' into local-classloader-tooling

6a75f57

Removed cleaner

52e6548

ctubbsii reviewed Jan 14, 2026

View reviewed changes

...ssloader/src/main/java/org/apache/accumulo/classloader/lcc/definition/ContextDefinition.java Outdated Show resolved Hide resolved

ctubbsii reviewed Jan 14, 2026

View reviewed changes

...ssloader/src/main/java/org/apache/accumulo/classloader/lcc/definition/ContextDefinition.java Outdated Show resolved Hide resolved

ctubbsii and others added 4 commits January 14, 2026 20:41

Merge branch 'main' into local-classloader-tooling

9d5ecbd

Merge branch 'main' into local-classloader-tooling

8eb2e1e

Merge branch 'local-classloader-tooling' of https://github.com/dlmari…

e4351d2

…on/accumulo-classloaders into local-classloader-tooling

Fix Test

710c104

Updated parameter order due to context name parameter being removed

5cb172a

dlmarion and others added 5 commits January 15, 2026 09:22

Apply suggestion from @keith-turner

514ba79

Co-authored-by: Keith Turner <kturner@apache.org>

Remove service file and use AutoService instead

a005755

Merge branch 'local-classloader-tooling' of https://github.com/dlmari…

e1a8b1c

…on/accumulo-classloaders into local-classloader-tooling

Merge branch 'main' into local-classloader-tooling

c550a28

Removed auto-service dependency

122bd6c

keith-turner reviewed Jan 15, 2026

View reviewed changes

Clean up README and pom

54ea87b

dlmarion commented Jan 15, 2026

View reviewed changes

modules/local-caching-classloader/README.md Outdated Show resolved Hide resolved

dlmarion added 2 commits January 15, 2026 19:08

Updated create-context-definition example in README

4258435

Implemented command line argument change suggestion

41b65f4

ctubbsii reviewed Jan 15, 2026

View reviewed changes

Code review cleanup

03737ab

* POM improvements * Use var and multi-catch in getReferencedFiles * Add newline to toJson() * Check for nulls before calling user consumer * Rename method in DeduplicationCache (values to forEach)

ctubbsii approved these changes Jan 15, 2026

View reviewed changes

Changes due to apache/accumulo#6062

c0f1978

Override mini jvm config for JMX

59bb5c7

dlmarion merged commit b4c3f7d into apache:main Jan 16, 2026
1 of 2 checks passed

dlmarion deleted the local-classloader-tooling branch January 16, 2026 15:14

dlmarion mentioned this pull request Jan 16, 2026

Create a cleanup utility #45

Open

	see the test method `MiniAccumuloClusterClassLoaderFactoryTest.getReferencedFiles`. This method attaches to the
	see the test method [MiniAccumuloClusterClassLoaderFactoryTest.getReferencedFiles](src/main/test/.../MiniAccumuloClusterClassLoaderFactoryTest.java). This method attaches to the

Add tools for ContextDefinition create and cleanup #33

Add tools for ContextDefinition create and cleanup #33

Uh oh!

Conversation

dlmarion commented Dec 3, 2025

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

dlmarion commented Dec 3, 2025

Uh oh!

Uh oh!

Uh oh!

ctubbsii left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

dlmarion commented Jan 15, 2026

Uh oh!

keith-turner Jan 15, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

ctubbsii left a comment

Choose a reason for hiding this comment

Uh oh!

keith-turner commented Jan 16, 2026

Uh oh!

dlmarion commented Jan 16, 2026

Uh oh!

dlmarion commented Jan 16, 2026

Uh oh!

keith-turner Jan 15, 2026 •

edited

Loading