Class DefaultPool

src/main/java/org/apache/groovy/runtime/async/DefaultPool.java:44–191

Default implementation of Pool. Sized pools (#fixed(int), #cpu()) use ForkJoinPool for work-stealing and parallel stream isolation. I/O pools (#virtual(), #io()) use virtual threads on JDK 21+. @see Pool @since 6.0.0

 * @since 6.0.0
 */
public final class DefaultPool implements Pool {

    // ---- Virtual thread detection ----------------------------------------

    private static final MethodHandle NEW_VT_EXECUTOR;
    private static final MethodType NEW_VT_EXECUTOR_TYPE = MethodType.methodType(ExecutorService.class);

    static {
        MethodHandle mh = null;
        try {
            mh = MethodHandles.lookup().findStatic(
                    Executors.class, "newVirtualThreadPerTaskExecutor",
                    NEW_VT_EXECUTOR_TYPE)
                    .asType(NEW_VT_EXECUTOR_TYPE);
        } catch (Throwable ignored) { }
        NEW_VT_EXECUTOR = mh;
    }

    private static final ScopedLocal<Pool> CURRENT_POOL = ScopedLocal.newInstance();

    // ---- Instance fields -------------------------------------------------

    private final ExecutorService executor;
    private final int poolSize;
    private final boolean virtualThreads;

    private DefaultPool(ExecutorService executor, int poolSize, boolean virtualThreads) {
        this.executor = executor;
        this.poolSize = poolSize;
        this.virtualThreads = virtualThreads;
    }

    // ---- Factory methods ------------------------------------------------

    /**
     * Creates a virtual-thread-per-task pool, or a cached daemon pool
     * as fallback on JDK &lt; 21.
     */
    public static Pool virtual() {
        if (NEW_VT_EXECUTOR != null) {
            try {
                ExecutorService es = (ExecutorService) NEW_VT_EXECUTOR.invokeExact();
                return new DefaultPool(es, Integer.MAX_VALUE, true);
            } catch (Throwable ignored) { }
        }
        AtomicLong counter = new AtomicLong();
        ExecutorService es = Executors.newCachedThreadPool(r -> {
            Thread t = new Thread(r, "groovy-pool-virtual-" + counter.incrementAndGet());
            t.setDaemon(true);
            return t;
        });
        return new DefaultPool(es, Integer.MAX_VALUE, false);
    }

    /**
     * Creates a fixed-size pool backed by {@link ForkJoinPool} for
     * work-stealing and parallel stream isolation.
     */