LineWriter, NonBlockingLineWriter & various fixes & clean-up by vorburger · Pull Request #18 · enola-dev/be

vorburger · 2025-10-04T23:45:42Z

No description provided.

…kingLineWriter Task

gemini-code-assist · 2025-10-04T23:46:00Z

Summary of Changes

Hello @vorburger, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the task execution framework by introducing new LineWriter abstractions for flexible and non-blocking output, and by refactoring the TaskExecutor for improved task lifecycle management and timeout handling. It also includes several clean-ups, documentation updates, and utility class additions to promote best practices for concurrency and logging, particularly in the context of Java's virtual threads.

Highlights

New LineWriter Abstractions: Introduced LineWriter interface and LineWriters utility class for flexible output handling, along with NonBlockingLineWriter for asynchronous, non-blocking line output, preventing backpressure and managing overflow.
TaskExecutor Refactoring: The TaskExecutor has been refactored to use FutureTask for improved task lifecycle management, including logging task completion and more robust timeout handling via a ScheduledExecutorService. The close() method now gracefully cancels running tasks.
Task Documentation and Best Practices: Updated Task Javadoc to provide guidance on using virtual threads, proper interruption handling, and explicitly discouraging the use of Thread.yield() due to its performance implications on modern Java.
Utility Class Relocation and Additions: The Threads utility class was moved to a more general dev.enola.common.concurrent package. New utility classes CheckedConsumer (for functional interfaces that can throw checked exceptions) and JulConfigurer (for basic Java Util Logging setup) were added.
Demo and Test Updates: The LongIncrementingTask demo was updated to utilize the new NonBlockingLineWriter and JulConfigurer, and Thread.yield() was removed. The SlowTask test was simplified by using the new Threads.sleep utility.

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Copilot

Pull Request Overview

This PR introduces LineWriter interfaces and NonBlockingLineWriter implementation for asynchronous logging, along with various fixes and improvements to the task execution framework. It includes migration from Thread.sleep to a safer Threads utility and general code cleanup.

Adds LineWriter interface and NonBlockingLineWriter for non-blocking output handling
Migrates from Thread.sleep to Threads.sleep utility for proper interrupt handling
Improves task execution framework with better timeout handling and logging

Reviewed Changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/dev/enola/common/log/JulConfigurer.java	New utility for configuring Java logging with custom formatter
src/dev/enola/common/function/CheckedConsumer.java	New functional interface for consumers that can throw checked exceptions
src/dev/enola/common/concurrent/Threads.java	Moved from demo package to common with visibility change
src/dev/enola/be/task/test/SlowTask.java	Updated to use Threads.sleep and Duration instead of raw milliseconds
src/dev/enola/be/task/demo/LongIncrementingTask.java	Enhanced with NonBlockingLineWriter integration and performance improvements
src/dev/enola/be/task/TaskWithoutInputOutput.java	New abstract base class for tasks without input/output
src/dev/enola/be/task/TaskExecutorServices.java	Removed unused close method
src/dev/enola/be/task/TaskExecutor.java	Improved timeout handling and task lifecycle management
src/dev/enola/be/task/TaskCallable.java	Removed duplicate endedAt call
src/dev/enola/be/task/Task.java	Enhanced documentation and improved toString output formatting
src/dev/enola/be/io/NonBlockingLineWriter.java	New non-blocking line writer implementation with overflow handling
src/dev/enola/be/io/LineWriters.java	Utility class with common LineWriter implementations
src/dev/enola/be/io/LineWriter.java	New interface for line-based output operations

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Copilot · 2025-10-04T23:46:19Z

+        JulConfigurer.configureRootLogger();
+
+        // Count to max, with sleep pause between each increment
+        var max = 1000000L;


[nitpick] The hardcoded value 1000000L should be extracted to a named constant to improve code readability and maintainability.

Copilot · 2025-10-04T23:46:20Z

+            while (!Thread.currentThread().isInterrupted()) {
+                if (overflow) {
+                    // https://en.wikipedia.org/wiki/Ellipsis
+                    delegate.println("[… output ... ※ ... truncated …]");


[nitpick] The overflow message should be extracted to a named constant to avoid duplication and improve maintainability.

Copilot · 2025-10-04T23:46:20Z

+            var timeout = task.timeout();
+            if (!timeout.isZero() && !timeout.isNegative()) {
+                timeoutScheduler.schedule(
+                        () -> futureTask.cancel(true), timeout.toMillis(), MILLISECONDS);


The timeout cancellation runs asynchronously but there's no handling for potential race conditions if the task completes just as the timeout fires. Consider checking task completion status before cancelling.

Suggested change

() -> futureTask.cancel(true), timeout.toMillis(), MILLISECONDS);

() -> {

if (!futureTask.isDone()) {

futureTask.cancel(true);

}

}, timeout.toMillis(), MILLISECONDS);

gemini-code-assist

Code Review

This pull request introduces a valuable LineWriter abstraction with a non-blocking implementation, which is excellent for handling task output without blocking. The refactoring of TaskExecutor to improve timeout handling and shutdown logic significantly enhances correctness and robustness. The addition of common utilities like Threads, CheckedConsumer, and JulConfigurer is also a good move. I've identified a critical concurrency bug and a high-severity usability issue in the new NonBlockingLineWriter that should be addressed.

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Copilot

Pull Request Overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 2 comments.

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

Copilot · 2025-10-04T23:53:05Z


        var input = new Input(max, sleep);
-        var task = new LongIncrementingTask(input, System.out::println);
+        var pumperTask = new NonBlockingLineWriter(13, LineWriters.SYSTEM_OUT);


The magic number 13 for queue capacity should be extracted to a named constant or variable to explain its significance and make it configurable.

Copilot · 2025-10-04T23:53:05Z

+            while (!Thread.currentThread().isInterrupted()) {
+                if (overflow) {
+                    // https://en.wikipedia.org/wiki/Ellipsis
+                    delegate.println("[… output ... ※ ... truncated …]");


The overflow message contains a mix of different ellipsis characters ('…' and '...'). Consider using consistent ellipsis formatting throughout the message.

Suggested change

delegate.println("[… output ... ※ ... truncated …]");

delegate.println("[… output … ※ … truncated …]");

vorburger added 7 commits October 4, 2025 23:43

feat: NonBlockingLineWriter & Co.

43c638f

feat: TaskExecutorServices log shutdown time etc.

c7c8d0f

fix: Task end logging much better now

518598d

fix: TaskExecutor.close() shutdown is very fast now even with NonBloc…

cd27c33

…kingLineWriter Task

fix: Remove Thread.yield()

02628df

clean: Use Threads.sleep() utility in SlowTask

3194202

clean: Remove useless TaskExecutorServices.close(Executor)

f313a28

Copilot AI review requested due to automatic review settings October 4, 2025 23:45

Copilot AI reviewed Oct 4, 2025

View reviewed changes

gemini-code-assist Bot reviewed Oct 4, 2025

View reviewed changes

Comment thread src/dev/enola/be/io/NonBlockingLineWriter.java Outdated

Comment thread src/dev/enola/be/io/NonBlockingLineWriter.java

fix: volatile boolean overflow in NonBlockingLineWriter

7a3acd9

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Copilot AI review requested due to automatic review settings October 4, 2025 23:52

vorburger added this pull request to the merge queue Oct 4, 2025

Copilot AI reviewed Oct 4, 2025

View reviewed changes

Merged via the queue into enola-dev:main with commit 659db1d Oct 4, 2025
1 check passed

vorburger deleted the LongIncrementingTask4 branch October 4, 2025 23:53

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LineWriter, NonBlockingLineWriter & various fixes & clean-up#18

LineWriter, NonBlockingLineWriter & various fixes & clean-up#18
vorburger merged 8 commits into
enola-dev:mainfrom
vorburger:LongIncrementingTask4

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-                        () -> futureTask.cancel(true), timeout.toMillis(), MILLISECONDS);
+                        () -> {
+                            if (!futureTask.isDone()) {
+                                futureTask.cancel(true);
+                            }
+                        }, timeout.toMillis(), MILLISECONDS);

	delegate.println("[… output ... ※ ... truncated …]");
	delegate.println("[… output … ※ … truncated …]");

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