ArC - introduce the CurrentContextFactory abstraction

- this API allows quarkus to supply an optimized backend for a context of a normal scope
- currently it's only used by the request context
- an extension can provide a custom factory via CurrentContextFactoryBuildItem

extensions/arc/deployment/src/main/java/io/quarkus/arc/deployment/ArcProcessor.java

@@ -512,7 +512,8 @@ public BeanContainerBuildItem generateResources(ArcConfig config, ArcRecorder re
             LiveReloadBuildItem liveReloadBuildItem,
             BuildProducer<GeneratedResourceBuildItem> generatedResource,
             BuildProducer<BytecodeTransformerBuildItem> bytecodeTransformer,
-            List<ReflectiveBeanClassBuildItem> reflectiveBeanClasses) throws Exception {
+            List<ReflectiveBeanClassBuildItem> reflectiveBeanClasses,
+            Optional<CurrentContextFactoryBuildItem> currentContextFactory) throws Exception {
 
         for (ValidationErrorBuildItem validationError : validationErrors) {
             for (Throwable error : validationError.getValues()) {
@@ -593,7 +594,8 @@ public void registerSubclass(DotName beanClassName, String subclassName) {
             reflectiveClasses.produce(new ReflectiveClassBuildItem(true, false, binding.name().toString()));
         }
 
-        ArcContainer container = recorder.getContainer(shutdown);
+        ArcContainer container = recorder.initContainer(shutdown,
+                currentContextFactory.isPresent() ? currentContextFactory.get().getFactory() : null);
         BeanContainer beanContainer = recorder.initBeanContainer(container,
                 beanContainerListenerBuildItems.stream().map(BeanContainerListenerBuildItem::getBeanContainerListener)
                         .collect(Collectors.toList()));

extensions/arc/deployment/src/main/java/io/quarkus/arc/deployment/CurrentContextFactoryBuildItem.java

@@ -0,0 +1,22 @@
+package io.quarkus.arc.deployment;
+
+import io.quarkus.arc.CurrentContextFactory;
+import io.quarkus.builder.item.SimpleBuildItem;
+import io.quarkus.runtime.RuntimeValue;
+
+/**
+ * An extension can provide a custom {@link CurrentContextFactory}.
+ */
+public final class CurrentContextFactoryBuildItem extends SimpleBuildItem {
+
+    private final RuntimeValue<CurrentContextFactory> factory;
+
+    public CurrentContextFactoryBuildItem(RuntimeValue<CurrentContextFactory> factory) {
+        this.factory = factory;
+    }
+
+    public RuntimeValue<CurrentContextFactory> getFactory() {
+        return factory;
+    }
+
+}

extensions/arc/runtime/src/main/java/io/quarkus/arc/runtime/ArcRecorder.java

@@ -14,6 +14,7 @@
 
 import io.quarkus.arc.Arc;
 import io.quarkus.arc.ArcContainer;
+import io.quarkus.arc.CurrentContextFactory;
 import io.quarkus.arc.InjectableBean;
 import io.quarkus.arc.InjectableBean.Kind;
 import io.quarkus.arc.impl.ArcContainerImpl;
@@ -36,8 +37,9 @@ public class ArcRecorder {
      */
     public static volatile Map<String, Supplier<?>> supplierMap;
 
-    public ArcContainer getContainer(ShutdownContext shutdown) throws Exception {
-        ArcContainer container = Arc.initialize();
+    public ArcContainer initContainer(ShutdownContext shutdown, RuntimeValue<CurrentContextFactory> currentContextFactory)
+            throws Exception {
+        ArcContainer container = Arc.initialize(currentContextFactory != null ? currentContextFactory.getValue() : null);
         shutdown.addShutdownTask(new Runnable() {
             @Override
             public void run() {

independent-projects/arc/runtime/src/main/java/io/quarkus/arc/Arc.java

@@ -11,18 +11,23 @@ public final class Arc {
 
     private static final AtomicReference<ArcContainerImpl> INSTANCE = new AtomicReference<>();
 
+    public static ArcContainer initialize() {
+        return initialize(null);
+    }
+
     /**
      *
+     * @param currentContextFactory
      * @return the initialized container
      */
-    public static ArcContainer initialize() {
+    public static ArcContainer initialize(CurrentContextFactory currentContextFactory) {
         ArcContainerImpl container = INSTANCE.get();
         if (container == null) {
             synchronized (INSTANCE) {
                 container = INSTANCE.get();
                 if (container == null) {
-                    container = new ArcContainerImpl();
                     // Set the container instance first because Arc.container() can be used within ArcContainerImpl.init()
+                    container = new ArcContainerImpl(currentContextFactory);
                     INSTANCE.set(container);
                     container.init();
                 }

independent-projects/arc/runtime/src/main/java/io/quarkus/arc/ArcContainer.java

@@ -179,4 +179,11 @@ public interface ArcContainer {
      * @return the default executor service
      */
     ExecutorService getExecutorService();
+
+    /**
+     *
+     * @return the factory
+     * @see CurrentContext
+     */
+    CurrentContextFactory getCurrentContextFactory();
 }

independent-projects/arc/runtime/src/main/java/io/quarkus/arc/CurrentContext.java

@@ -0,0 +1,31 @@
+package io.quarkus.arc;
+
+import io.quarkus.arc.InjectableContext.ContextState;
+
+/**
+ * Represents the current context of a normal scope.
+ *
+ * @param <T>
+ * @see CurrentContextFactory
+ */
+public interface CurrentContext<T extends ContextState> {
+
+    /**
+     *
+     * @return the current state
+     */
+    T get();
+
+    /**
+     * Sets the current state.
+     *
+     * @param state
+     */
+    void set(T state);
+
+    /**
+     * Removes the current state.
+     */
+    void remove();
+
+}

independent-projects/arc/runtime/src/main/java/io/quarkus/arc/CurrentContextFactory.java

@@ -0,0 +1,15 @@
+package io.quarkus.arc;
+
+import io.quarkus.arc.InjectableContext.ContextState;
+import java.lang.annotation.Annotation;
+
+/**
+ * This factory can be used to create a new {@link CurrentContext} for a normal scope, e.g. for
+ * {@link javax.enterprise.context.RequestScoped}. It's usually not necessary for shared contexts, such as
+ * {@link javax.enterprise.context.ApplicationScoped}.
+ */
+public interface CurrentContextFactory {
+
+    <T extends ContextState> CurrentContext<T> create(Class<? extends Annotation> scope);
+
+}

independent-projects/arc/runtime/src/main/java/io/quarkus/arc/InjectableContext.java

@@ -85,9 +85,6 @@ default boolean isNormal() {
         return getScope().isAnnotationPresent(NormalScope.class);
     }
 
-    /**
-    *
-    */
     interface ContextState {
 
         /**

independent-projects/arc/runtime/src/main/java/io/quarkus/arc/impl/ArcContainerImpl.java

@@ -6,6 +6,7 @@
 import io.quarkus.arc.ArcContainer;
 import io.quarkus.arc.Components;
 import io.quarkus.arc.ComponentsProvider;
+import io.quarkus.arc.CurrentContextFactory;
 import io.quarkus.arc.InjectableBean;
 import io.quarkus.arc.InjectableContext;
 import io.quarkus.arc.InjectableDecorator;
@@ -46,6 +47,7 @@
 import javax.enterprise.context.Destroyed;
 import javax.enterprise.context.Initialized;
 import javax.enterprise.context.NormalScope;
+import javax.enterprise.context.RequestScoped;
 import javax.enterprise.event.Event;
 import javax.enterprise.inject.AmbiguousResolutionException;
 import javax.enterprise.inject.Any;
@@ -95,7 +97,9 @@ public class ArcContainerImpl implements ArcContainer {
 
     private volatile ExecutorService executorService;
 
-    public ArcContainerImpl() {
+    private final CurrentContextFactory currentContextFactory;
+
+    public ArcContainerImpl(CurrentContextFactory currentContextFactory) {
         id = String.valueOf(ID_GENERATOR.incrementAndGet());
         running = new AtomicBoolean(true);
         List<InjectableBean<?>> beans = new ArrayList<>();
@@ -105,10 +109,12 @@ public ArcContainerImpl() {
         List<InjectableObserverMethod<?>> observers = new ArrayList<>();
         Map<Class<? extends Annotation>, Set<Annotation>> transitiveInterceptorBindings = new HashMap<>();
         Map<String, Set<String>> qualifierNonbindingMembers = new HashMap<>();
+        this.currentContextFactory = currentContextFactory == null ? new ThreadLocalCurrentContextFactory()
+                : currentContextFactory;
 
         applicationContext = new ApplicationContext();
         singletonContext = new SingletonContext();
-        requestContext = new RequestContext();
+        requestContext = new RequestContext(this.currentContextFactory.create(RequestScoped.class));
         contexts = new HashMap<>();
         putContext(requestContext);
         putContext(applicationContext);
@@ -342,6 +348,11 @@ public void setExecutor(ExecutorService executor) {
         this.executorService = executor;
     }
 
+    @Override
+    public CurrentContextFactory getCurrentContextFactory() {
+        return currentContextFactory;
+    }
+
     @Override
     public String toString() {
         return "ArcContainerImpl [id=" + id + ", running=" + running + ", beans=" + beans.size() + ", observers="

independent-projects/arc/runtime/src/main/java/io/quarkus/arc/impl/RequestContext.java

@@ -1,6 +1,7 @@
 package io.quarkus.arc.impl;
 
 import io.quarkus.arc.ContextInstanceHandle;
+import io.quarkus.arc.CurrentContext;
 import io.quarkus.arc.InjectableBean;
 import io.quarkus.arc.ManagedContext;
 import io.quarkus.arc.impl.EventImpl.Notifier;
@@ -33,14 +34,14 @@ class RequestContext implements ManagedContext {
 
     private static final Logger LOGGER = Logger.getLogger(RequestContext.class.getPackage().getName());
 
-    // It's a normal scope so there may be no more than one mapped instance per contextual type per thread
-    private final ThreadLocal<RequestContextState> currentContext = new ThreadLocal<>();
+    private final CurrentContext<RequestContextState> currentContext;
 
     private final LazyValue<Notifier<Object>> initializedNotifier;
     private final LazyValue<Notifier<Object>> beforeDestroyedNotifier;
     private final LazyValue<Notifier<Object>> destroyedNotifier;
 
-    public RequestContext() {
+    public RequestContext(CurrentContext<RequestContextState> currentContext) {
+        this.currentContext = currentContext;
         this.initializedNotifier = new LazyValue<>(RequestContext::createInitializedNotifier);
         this.beforeDestroyedNotifier = new LazyValue<>(RequestContext::createBeforeDestroyedNotifier);
         this.destroyedNotifier = new LazyValue<>(RequestContext::createDestroyedNotifier);
@@ -62,17 +63,16 @@ public <T> T getIfActive(Contextual<T> contextual, Function<Contextual<T>, Creat
         }
         RequestContextState ctxState = currentContext.get();
         if (ctxState == null) {
-            // Thread local not set - context is not active!
+            // Context is not active!
             return null;
         }
-        Map<Contextual<?>, ContextInstanceHandle<?>> ctxMap = currentContext.get().value;
-        ContextInstanceHandle<T> instance = (ContextInstanceHandle<T>) ctxMap.get(contextual);
+        ContextInstanceHandle<T> instance = (ContextInstanceHandle<T>) ctxState.map.get(contextual);
         if (instance == null) {
             CreationalContext<T> creationalContext = creationalContextFun.apply(contextual);
             // Bean instance does not exist - create one if we have CreationalContext
             instance = new ContextInstanceHandleImpl<T>((InjectableBean<T>) contextual,
                     contextual.create(creationalContext), creationalContext);
-            ctxMap.put(contextual, instance);
+            ctxState.map.put(contextual, instance);
         }
         return instance.get();
     }
@@ -82,7 +82,6 @@ public <T> T get(Contextual<T> contextual, CreationalContext<T> creationalContex
         T result = getIfActive(contextual,
                 CreationalContextImpl.unwrap(Objects.requireNonNull(creationalContext, "CreationalContext must not be null")));
         if (result == null) {
-            // Thread local not set - context is not active!
             throw new ContextNotActiveException();
         }
         return result;
@@ -96,12 +95,11 @@ public <T> T get(Contextual<T> contextual) {
         if (!Scopes.scopeMatches(this, bean)) {
             throw Scopes.scopeDoesNotMatchException(this, bean);
         }
-        Map<Contextual<?>, ContextInstanceHandle<?>> ctx = currentContext.get().value;
-        if (ctx == null) {
-            // Thread local not set - context is not active!
+        RequestContextState state = currentContext.get();
+        if (state == null) {
             throw new ContextNotActiveException();
         }
-        ContextInstanceHandle<T> instance = (ContextInstanceHandle<T>) ctx.get(contextual);
+        ContextInstanceHandle<T> instance = (ContextInstanceHandle<T>) state.map.get(contextual);
         return instance == null ? null : instance.get();
     }
 
@@ -112,12 +110,12 @@ public boolean isActive() {
 
     @Override
     public void destroy(Contextual<?> contextual) {
-        Map<Contextual<?>, ContextInstanceHandle<?>> ctx = currentContext.get().value;
-        if (ctx == null) {
-            // Thread local not set - context is not active!
+        RequestContextState state = currentContext.get();
+        if (state == null) {
+            // Context is not active
             throw new ContextNotActiveException();
         }
-        ContextInstanceHandle<?> instance = ctx.remove(contextual);
+        ContextInstanceHandle<?> instance = state.map.remove(contextual);
         if (instance != null) {
             instance.destroy();
         }
@@ -131,7 +129,7 @@ public void activate(ContextState initialState) {
             fireIfNotEmpty(initializedNotifier);
         } else {
             if (initialState instanceof RequestContextState) {
-                currentContext.set(((RequestContextState) initialState));
+                currentContext.set((RequestContextState) initialState);
             } else {
                 throw new IllegalArgumentException("Invalid initial state: " + initialState.getClass().getName());
             }
@@ -140,20 +138,16 @@ public void activate(ContextState initialState) {
 
     @Override
     public ContextState getState() {
-        RequestContextState ctx = currentContext.get();
-        if (ctx == null) {
+        RequestContextState state = currentContext.get();
+        if (state == null) {
             // Thread local not set - context is not active!
             throw new ContextNotActiveException();
         }
-        return ctx;
+        return state;
     }
 
     public ContextState getStateIfActive() {
-        RequestContextState ctx = currentContext.get();
-        if (ctx == null) {
-            return null;
-        }
-        return ctx;
+        return currentContext.get();
     }
 
     @Override
@@ -175,31 +169,26 @@ public void destroy(ContextState state) {
         if (state instanceof RequestContextState) {
             RequestContextState reqState = ((RequestContextState) state);
             reqState.isValid.set(false);
-            destroy(reqState.value);
-        } else {
-            throw new IllegalArgumentException("Invalid state: " + state.getClass().getName());
-        }
-    }
-
-    private void destroy(Map<Contextual<?>, ContextInstanceHandle<?>> currentContext) {
-        if (currentContext != null) {
-            synchronized (currentContext) {
+            synchronized (state) {
+                Map<Contextual<?>, ContextInstanceHandle<?>> map = ((RequestContextState) state).map;
                 // Fire an event with qualifier @BeforeDestroyed(RequestScoped.class) if there are any observers for it
                 try {
                     fireIfNotEmpty(beforeDestroyedNotifier);
                 } catch (Exception e) {
                     LOGGER.warn("An error occurred during delivery of the @BeforeDestroyed(RequestScoped.class) event", e);
                 }
                 //Performance: avoid an iterator on the map elements
-                currentContext.forEach(this::destroyContextElement);
+                map.forEach(this::destroyContextElement);
                 // Fire an event with qualifier @Destroyed(RequestScoped.class) if there are any observers for it
                 try {
                     fireIfNotEmpty(destroyedNotifier);
                 } catch (Exception e) {
                     LOGGER.warn("An error occurred during delivery of the @Destroyed(RequestScoped.class) event", e);
                 }
-                currentContext.clear();
+                map.clear();
             }
+        } else {
+            throw new IllegalArgumentException("Invalid state implementation: " + state.getClass().getName());
         }
     }
 
@@ -238,17 +227,17 @@ private static Notifier<Object> createDestroyedNotifier() {
 
     static class RequestContextState implements ContextState {
 
-        private final ConcurrentMap<Contextual<?>, ContextInstanceHandle<?>> value;
+        private final Map<Contextual<?>, ContextInstanceHandle<?>> map;
         private final AtomicBoolean isValid;
 
         RequestContextState(ConcurrentMap<Contextual<?>, ContextInstanceHandle<?>> value) {
-            this.value = value;
+            this.map = Objects.requireNonNull(value);
             this.isValid = new AtomicBoolean(true);
         }
 
         @Override
         public Map<InjectableBean<?>, Object> getContextualInstances() {
-            return value.values().stream()
+            return map.values().stream()
                     .collect(Collectors.toUnmodifiableMap(ContextInstanceHandle::getBean, ContextInstanceHandle::get));
         }