feat: virtual thread support by csviri · Pull Request #3603 · operator-framework/java-operator-sdk

csviri · 2026-09-07T13:58:44Z

Introduces feature flag to use virtual threads instead of standard ThreadPool. The concurrency limit also applies for this this new mode.

Signed-off-by: Attila Mészáros a_meszaros@apple.com

coderabbitai · 2026-09-07T13:58:50Z

Important

Review skipped

Auto reviews are disabled on base/target branches other than the default branch.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: ecdadcd0-a73d-4f61-a782-9a4b5e0e4cf4

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

🔍 Trigger review

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

_{Comment @coderabbitai help to get the list of available commands.}

Signed-off-by: Attila Mészáros <a_meszaros@apple.com>

Copilot

🟡 Changes recommended

One or more issues must be addressed before approval.

Get a fresh assessment by requesting another Copilot review.

Pull request overview

Adds optional Java 21 virtual-thread execution support while preserving configured concurrency limits and Java 17 compatibility.

Changes:

Adds virtual-thread configuration and property loading.
Implements bounded and unbounded virtual-thread executors with fallback behavior.
Adds unit, integration, and documentation coverage.

File summaries

File	Description
operator-framework/src/test/java/io/javaoperatorsdk/operator/config/loader/ConfigLoaderTest.java	Updated as part of this pull request.
operator-framework/src/test/java/io/javaoperatorsdk/operator/baseapi/virtualthreads/VirtualThreadsTestReconciler.java	Updated as part of this pull request.
operator-framework/src/test/java/io/javaoperatorsdk/operator/baseapi/virtualthreads/VirtualThreadsIT.java	Updated as part of this pull request.
operator-framework/src/test/java/io/javaoperatorsdk/operator/baseapi/virtualthreads/VirtualThreadsCustomResource.java	Updated as part of this pull request.
operator-framework/src/main/java/io/javaoperatorsdk/operator/config/loader/ConfigLoader.java	Updated as part of this pull request.
operator-framework-core/src/test/java/io/javaoperatorsdk/operator/api/config/VirtualThreadsTest.java	Updated as part of this pull request.
operator-framework-core/src/test/java/io/javaoperatorsdk/operator/api/config/ConfigurationServiceOverriderTest.java	Updated as part of this pull request.
operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/VirtualThreads.java	Updated as part of this pull request.
operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/ExecutorServiceManager.java	Updated as part of this pull request.
operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/ConfigurationServiceOverrider.java	Updated as part of this pull request.
operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/ConfigurationService.java	Updated as part of this pull request.
docs/content/en/docs/documentation/operations/configuration.md	Updated as part of this pull request.

Review details

Suppressed comments (1)

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/VirtualThreads.java:143

This implementation creates and parks one virtual thread for every submitted task before acquiring a permit. Unlike the previous fixed pool, a large reconciliation backlog therefore becomes one live virtual-thread object per queued event, so a burst or outage can consume substantial heap/thread-scheduler resources even though only maxConcurrency tasks execute. Please use a bounded dispatcher/queue (or otherwise cap pending submissions) so the concurrency limit also bounds resource usage, rather than relying on virtual threads being cheap.

      delegate.execute(
          () -> {
            try {
              permits.acquire();

Files reviewed: 12/12 changed files
Comments generated: 1
Review effort level: Lite

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

+    private BoundedExecutorService(ExecutorService delegate, int maxConcurrency) {
+      this.delegate = delegate;
+      // fair, so that tasks run roughly in submission order as they would on a thread pool
+      this.permits = new Semaphore(maxConcurrency, true);


Copilot

🟡 Changes recommended

Address the shutdown/cancellation defect, reject zero concurrency limits, and clarify the scheduled-executor documentation.

Get a fresh assessment by requesting another Copilot review.

Review details

Suppressed comments (2)

docs/content/en/docs/documentation/operations/configuration.md:37

This says that all framework internal housekeeping runs on virtual threads, but ExecutorServiceManager deliberately keeps scheduledExecutorService on platform threads even when the flag is enabled (see ExecutorServiceManager.java:171-173). Please narrow this statement to the executors that are switched, or explicitly mention the scheduled executor exception so the user-facing documentation matches the implementation.

When enabled, reconciliations, dependent resource workflows and the framework's internal
housekeeping (starting the informers, for example) all run on virtual threads.

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/VirtualThreads.java:135

Unlike Executors.newFixedThreadPool, this constructor accepts maxConcurrency == 0 because Semaphore(0) is valid. Every submitted task then blocks forever waiting for a permit, so the new public ExecutorServiceManager.newBoundedExecutorService(0, true) can silently create a permanently hanging executor instead of rejecting the invalid limit. Validate that the limit is at least 1 before creating the semaphore (and keep the behavior consistent with the platform-backed path).

    private BoundedExecutorService(ExecutorService delegate, int maxConcurrency) {
      this.delegate = delegate;
      // fair, so that tasks run roughly in submission order as they would on a thread pool
      this.permits = new Semaphore(maxConcurrency, true);

Files reviewed: 12/12 changed files
Comments generated: 1
Review effort level: Lite

+    public List<Runnable> shutdownNow() {
+      return delegate.shutdownNow();
+    }


Signed-off-by: Attila Mészáros <a_meszaros@apple.com>

xstefank

Approving because I know that I will be probably only one against a global virtual thread flag here.

But maybe you want to wait for our next JUG session :) - https://www.meetup.com/brno-java-meetup/events/316579260/?eventOrigin=group_upcoming_events

xstefank · 2026-09-18T09:43:28Z

+
+    private BoundedExecutorService(ExecutorService delegate, int maxConcurrency) {
+      this.delegate = delegate;
+      // fair, so that tasks run roughly in submission order as they would on a thread pool


this seems like a piece of agent communication rather than useful comment

csviri · 2026-09-18T11:56:09Z

Approving because I know that I will be probably only one against a global virtual thread flag here.

But maybe you want to wait for our next JUG session :) - https://www.meetup.com/brno-java-meetup/events/316579260/?eventOrigin=group_upcoming_events

What would you propose as an alternative?

Signed-off-by: Attila Mészáros <a_meszaros@apple.com>

openshift-ci Bot added the do-not-merge/work-in-progress Indicates that a PR should not merge because it is a work in progress. label Sep 7, 2026

csviri changed the title ~~feat: virtual thread support~~ [WIP] feat: virtual thread support Sep 7, 2026

csviri linked an issue Sep 9, 2026 that may be closed by this pull request

Support for Virtual Threads #3538

Open

feat: virtual thread support

cacd8be

Signed-off-by: Attila Mészáros <a_meszaros@apple.com>

csviri force-pushed the virtual-threads branch from 609a12f to cacd8be Compare September 17, 2026 06:23

wip

4b32b10

Signed-off-by: Attila Mészáros <a_meszaros@apple.com>

csviri marked this pull request as ready for review September 17, 2026 06:52

Copilot AI lite review requested due to automatic review settings September 17, 2026 06:52

openshift-ci Bot requested review from metacosm and xstefank September 17, 2026 06:52

Copilot started reviewing on behalf of csviri September 17, 2026 06:53 View session

Copilot AI reviewed Sep 17, 2026

View reviewed changes

csviri requested a lite review from Copilot September 17, 2026 07:17

csviri changed the title ~~[WIP] feat: virtual thread support~~ feat: virtual thread support Sep 17, 2026

openshift-ci Bot removed the do-not-merge/work-in-progress Indicates that a PR should not merge because it is a work in progress. label Sep 17, 2026

Copilot started reviewing on behalf of csviri September 17, 2026 07:18 View session

Copilot AI reviewed Sep 17, 2026

View reviewed changes

Comment thread ...ator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/VirtualThreads.java

Comment on lines +167 to +169

public List<Runnable> shutdownNow() {

return delegate.shutdownNow();

}

wip

58fd1a5

Signed-off-by: Attila Mészáros <a_meszaros@apple.com>

xstefank approved these changes Sep 18, 2026

View reviewed changes

remove unnecessary comment

1300484

Signed-off-by: Attila Mészáros <a_meszaros@apple.com>

Navigation Menu

feat: virtual thread support - #3603

feat: virtual thread support#3603
csviri wants to merge 4 commits into
operator-framework:nextfrom
csviri:virtual-threads

csviri commented Sep 7, 2026 •

edited

Loading

Uh oh!

coderabbitai Bot commented Sep 7, 2026 •

edited

Loading

Review skipped

Uh oh!

Copilot AI left a comment

Uh oh!

Copilot AI left a comment

Uh oh!

xstefank left a comment

Uh oh!

xstefank Sep 18, 2026

Uh oh!

csviri commented Sep 18, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

Conversation

csviri commented Sep 7, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

coderabbitai Bot commented Sep 7, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Review skipped

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

🟡 Changes recommended

Suppressed comments (1)

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

🟡 Changes recommended

Suppressed comments (2)

Uh oh!

xstefank left a comment

Choose a reason for hiding this comment

Uh oh!

xstefank Sep 18, 2026

Choose a reason for hiding this comment

Uh oh!

csviri commented Sep 18, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

csviri commented Sep 7, 2026 •

edited

Loading

coderabbitai Bot commented Sep 7, 2026 •

edited

Loading