Loom support moved to ThreadPoolSupplier

common/configurable/src/main/java/io/helidon/common/configurable/ThreadPoolSupplier.java

@@ -58,6 +58,7 @@ public final class ThreadPoolSupplier implements Supplier<ExecutorService> {
     private final int growthRate;
     private final ThreadPool.RejectionHandler rejectionHandler;
     private final LazyValue<ExecutorService> lazyValue = LazyValue.create(() -> Contexts.wrap(getThreadPool()));
+    private final boolean useVirtualThreads;
 
     private ThreadPoolSupplier(Builder builder) {
         this.corePoolSize = builder.corePoolSize;
@@ -71,6 +72,7 @@ private ThreadPoolSupplier(Builder builder) {
         this.growthThreshold = builder.growthThreshold;
         this.growthRate = builder.growthRate;
         this.rejectionHandler = builder.rejectionHandler == null ? DEFAULT_REJECTION_POLICY : builder.rejectionHandler;
+        this.useVirtualThreads = builder.useVirtualThreads || builder.virtualThreadsEnforced;
     }
 
     /**
@@ -102,7 +104,14 @@ public static ThreadPoolSupplier create() {
         return builder().build();
     }
 
-    ThreadPool getThreadPool() {
+    ExecutorService getThreadPool() {
+        if (useVirtualThreads) {
+            if (VirtualExecutorUtil.isVirtualSupported()) {
+                LOGGER.fine("Using unbounded virtual executor service for pool " + name);
+                return VirtualExecutorUtil.executorService();
+            }
+        }
+
         ThreadPool result = ThreadPool.create(name,
                                               corePoolSize,
                                               maxPoolSize,
@@ -149,6 +158,8 @@ public static final class Builder implements io.helidon.common.Builder<ThreadPoo
         private int growthRate = DEFAULT_GROWTH_RATE;
         private ThreadPool.RejectionHandler rejectionHandler = DEFAULT_REJECTION_POLICY;
         private String name;
+        private boolean useVirtualThreads;
+        private boolean virtualThreadsEnforced;
 
         private Builder() {
         }
@@ -162,6 +173,13 @@ public ThreadPoolSupplier build() {
                 rejectionHandler = DEFAULT_REJECTION_POLICY;
             }
 
+            if (virtualThreadsEnforced) {
+                if (!VirtualExecutorUtil.isVirtualSupported()) {
+                    throw new IllegalStateException("Virtual threads are required, yet not available on this JVM. "
+                                                            + "Please use a Loom build.");
+                }
+            }
+
             return new ThreadPoolSupplier(this);
         }
 
@@ -390,13 +408,48 @@ public Builder config(Config config) {
             config.get("growth-rate").asInt().ifPresent(value -> {
                 warnExperimental("growth-rate");
                 growthRate(value);
-
+           });
+            config.get("virtual-threads").asBoolean().ifPresent(value -> {
+                warnExperimental("virtual-threads");
+                virtualIfAvailable(value);
+            });
+            config.get("virtual-enforced").asBoolean().ifPresent(value -> {
+                warnExperimental("virtual-enforced");
+                virtualEnforced(value);
             });
             return this;
         }
 
         private void warnExperimental(String key) {
             LOGGER.warning(String.format("Config key \"executor-service.%s\" is EXPERIMENTAL and subject to change.", key));
         }
+
+        /**
+         * When configured to {@code true}, virtual thread executor service must be available, otherwise the built
+         * executor would fail to start.
+         *
+         * @param enforceVirtualThreads whether to enforce virtual threads, defaults to {@code false}
+         * @return updated builder instance
+         * @see #virtualIfAvailable(boolean)
+         */
+        public Builder virtualEnforced(boolean enforceVirtualThreads) {
+            this.virtualThreadsEnforced = enforceVirtualThreads;
+            return this;
+        }
+
+        /**
+         * When configured to {@code true}, an unbounded virtual executor service (project Loom) will be used
+         * if available.
+         * This is an experimental feature.
+         * <p>
+         * If enabled and available, all other configuration options of this executor service are ignored!
+         *
+         * @param useVirtualThreads whether to use virtual threads or not, defaults to {@code false}
+         * @return updated builder instance
+         */
+        public Builder virtualIfAvailable(boolean useVirtualThreads) {
+            this.useVirtualThreads = useVirtualThreads;
+            return this;
+        }
     }
 }

common/configurable/src/main/java/io/helidon/common/configurable/VirtualExecutorUtil.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2021 Oracle and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.helidon.common.configurable;
+
+import java.lang.reflect.Method;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+import io.helidon.common.LazyValue;
+
+/**
+ * A utility class to handle virtual threads (project Loom).
+ */
+final class VirtualExecutorUtil {
+    private static final Logger LOGGER = Logger.getLogger(VirtualExecutorUtil.class.getName());
+    private static final LazyValue<Boolean> SUPPORTED = LazyValue.create(VirtualExecutorUtil::findSupported);
+    private static final LazyValue<ExecutorService> EXECUTOR_SERVICE = LazyValue.create(VirtualExecutorUtil::findExecutor);
+
+    private VirtualExecutorUtil() {
+    }
+
+    static boolean isVirtualSupported() {
+        return SUPPORTED.get();
+    }
+
+    static ExecutorService executorService() {
+        ExecutorService result = EXECUTOR_SERVICE.get();
+        if (result == null) {
+            throw new IllegalStateException("Virtual executor service is not supported on this JVM");
+        }
+        return result;
+    }
+
+    private static boolean findSupported() {
+        try {
+            // the method is intentionally NOT CACHED in static context, to support differences between build
+            // and runtime environments (support for GraalVM native image)
+            findMethod();
+            return true;
+        } catch (final ReflectiveOperationException e) {
+            LOGGER.log(Level.FINEST, "Loom virtual executor service not available", e);
+        }
+
+        return false;
+    }
+
+    private static ExecutorService findExecutor() {
+        try {
+            // the method is intentionally NOT CACHED in static context, to support differences between build
+            // and runtime environments (support for GraalVM native image)
+            return (ExecutorService) findMethod().invoke(null);
+        } catch (final ReflectiveOperationException e) {
+            LOGGER.log(Level.FINEST, "Loom virtual executor service not available", e);
+        }
+
+        return null;
+    }
+
+    private static Method findMethod() throws ReflectiveOperationException {
+        return Executors.class.getDeclaredMethod("newVirtualThreadExecutor");
+    }
+}

common/configurable/src/test/java/io/helidon/common/configurable/ThreadPoolSupplierTest.java

@@ -34,6 +34,7 @@
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
 
+import static org.hamcrest.CoreMatchers.instanceOf;
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.CoreMatchers.notNullValue;
 import static org.hamcrest.CoreMatchers.startsWith;
@@ -50,19 +51,25 @@ class ThreadPoolSupplierTest {
 
     @BeforeAll
     static void initClass() {
-        defaultInstance = ThreadPoolSupplier.create().getThreadPool();
+        defaultInstance = ensureOurExecutor(ThreadPoolSupplier.create().getThreadPool());
 
-        builtInstance = ThreadPoolSupplier.builder()
+        builtInstance = ensureOurExecutor(ThreadPoolSupplier.builder()
                                           .threadNamePrefix("thread-pool-unit-test-")
                                           .corePoolSize(2)
                                           .daemon(true)
                                           .prestart(true)
                                           .queueCapacity(10)
                                           .build()
-                                          .getThreadPool();
+                                          .getThreadPool());
 
-        configuredInstance = ThreadPoolSupplier.create(Config.create().get("unit.thread-pool"))
-                                               .getThreadPool();
+        configuredInstance = ensureOurExecutor(ThreadPoolSupplier.create(Config.create().get("unit.thread-pool"))
+                                               .getThreadPool());
+    }
+
+    private static ThreadPoolExecutor ensureOurExecutor(ExecutorService threadPool) {
+        // thread pool should be our implementation, unless Loom virtual threads are used
+        assertThat(threadPool, instanceOf(ThreadPoolExecutor.class));
+        return (ThreadPoolExecutor) threadPool;
     }
 
     @Test

microprofile/server/src/main/java/io/helidon/microprofile/server/ServerCdiExtension.java

@@ -31,7 +31,6 @@
 import java.util.Set;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Supplier;
@@ -56,7 +55,6 @@
 import io.helidon.common.configurable.ServerThreadPoolSupplier;
 import io.helidon.common.http.Http;
 import io.helidon.config.Config;
-import io.helidon.config.DeprecatedConfig;
 import io.helidon.microprofile.cdi.BuildTimeStart;
 import io.helidon.microprofile.cdi.RuntimeStart;
 import io.helidon.webserver.KeyPerformanceIndicatorSupport;
@@ -170,34 +168,12 @@ private void startServer(@Observes @Priority(PLATFORM_AFTER + 100) @Initialized(
         // make sure all configuration is in place
         if (null == jaxRsExecutorService) {
             Config serverConfig = config.get("server");
-            final java.lang.reflect.Method m;
-            if (DeprecatedConfig.get(serverConfig, "executor-service.virtual-threads", "virtual-threads")
-                    .asBoolean().orElse(false)) {
-                java.lang.reflect.Method temp = null;
-                try {
-                    temp = Executors.class.getDeclaredMethod("newVirtualThreadExecutor");
-                } catch (final ReflectiveOperationException notLoomEarlyAccess) {
-                    temp = null;
-                } finally {
-                    m = temp;
-                }
-            } else {
-                m = null;
-            }
-            if (m != null) {
-                jaxRsExecutorService = () -> {
-                    try {
-                        return (ExecutorService) m.invoke(null);
-                    } catch (final ReflectiveOperationException reflectiveOperationException) {
-                        throw new IllegalStateException(reflectiveOperationException.getMessage(), reflectiveOperationException);
-                    }
-                };
-            } else {
-                jaxRsExecutorService = ServerThreadPoolSupplier.builder()
-                    .name("server")
-                    .config(serverConfig.get("executor-service"))
-                    .build();
-            }
+
+            // support for Loom is built into the thread pool supplier
+            jaxRsExecutorService = ServerThreadPoolSupplier.builder()
+                .name("server")
+                .config(serverConfig.get("executor-service"))
+                .build();
         }
 
         // redirect to the first page when root is accessed (if configured)

webserver/jersey/src/main/java/io/helidon/webserver/jersey/AsyncExecutorProvider.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 Oracle and/or its affiliates.
+ * Copyright (c) 2020, 2021 Oracle and/or its affiliates.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,7 +18,6 @@
 
 import java.util.Objects;
 import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
 import java.util.function.Supplier;
 
 import io.helidon.common.configurable.ThreadPoolSupplier;
@@ -37,36 +36,15 @@ class AsyncExecutorProvider implements ExecutorServiceProvider {
 
     static ExecutorServiceProvider create(Config config) {
         Config asyncExecutorServiceConfig = config.get("async-executor-service");
-        final java.lang.reflect.Method m;
-        if (asyncExecutorServiceConfig.get("virtual-threads").asBoolean().orElse(false)) {
-            java.lang.reflect.Method temp = null;
-            try {
-                temp = Executors.class.getDeclaredMethod("newVirtualThreadExecutor");
-            } catch (final ReflectiveOperationException notLoom) {
-                temp = null;
-            } finally {
-                m = temp;
-            }
-        } else {
-            m = null;
-        }
-        if (m != null) {
-            return new AsyncExecutorProvider(() -> {
-                try {
-                    return (ExecutorService) m.invoke(null);
-                } catch (final ReflectiveOperationException reflectiveOperationException) {
-                    throw new IllegalStateException(reflectiveOperationException.getMessage(), reflectiveOperationException);
-                }
-            });
-        } else {
-            return new AsyncExecutorProvider(ThreadPoolSupplier.builder()
+
+        // Loom support is moved to thread pool supplier
+        return new AsyncExecutorProvider(ThreadPoolSupplier.builder()
                                                  .corePoolSize(1)
                                                  .maxPoolSize(10)
                                                  .prestart(false)
                                                  .threadNamePrefix("helidon-jersey-async")
                                                  .config(asyncExecutorServiceConfig)
                                                  .build());
-        }
     }
 
     static ExecutorServiceProvider create(ExecutorService executor) {