Add access mode

src/main/java/io/vertx/core/Context.java

@@ -17,7 +17,8 @@
 import io.vertx.codegen.annotations.VertxGen;
 import io.vertx.core.impl.VertxThread;
 import io.vertx.core.json.JsonObject;
-import io.vertx.core.spi.context.ContextKey;
+import io.vertx.core.spi.context.locals.AccessMode;
+import io.vertx.core.spi.context.locals.ContextKey;
 
 import java.util.Collections;
 import java.util.List;
@@ -254,7 +255,9 @@ default List<String> processArgs() {
    * @return the local data
    */
   @GenIgnore
-  <T> T getLocal(ContextKey<T> key);
+  default <T> T getLocal(ContextKey<T> key) {
+    return getLocal(key, AccessMode.CONCURRENT);
+  }
 
   /**
    * Get some local data from the context, when it does not exist the {@code initialValueSupplier} is called to obtain
@@ -268,7 +271,9 @@ default List<String> processArgs() {
    * @return the local data
    */
   @GenIgnore
-  <T> T getLocal(ContextKey<T> key, Supplier<? extends T> initialValueSupplier);
+  default <T> T getLocal(ContextKey<T> key, Supplier<? extends T> initialValueSupplier) {
+    return getLocal(key, AccessMode.CONCURRENT, initialValueSupplier);
+  }
 
   /**
    * Put some local data in the context.
@@ -279,7 +284,9 @@ default List<String> processArgs() {
    * @param value  the data
    */
   @GenIgnore
-  <T> void putLocal(ContextKey<T> key, T value);
+  default <T> void putLocal(ContextKey<T> key, T value) {
+    putLocal(key, AccessMode.CONCURRENT, value);
+  }
 
   /**
    * Remove some local data from the context.
@@ -288,7 +295,52 @@ default List<String> processArgs() {
    */
   @GenIgnore
   default <T> void removeLocal(ContextKey<T> key) {
-    putLocal(key, null);
+    putLocal(key, AccessMode.CONCURRENT, null);
+  }
+
+  /**
+   * Get some local data from the context.
+   *
+   * @param key  the key of the data
+   * @param <T>  the type of the data
+   * @return the local data
+   */
+  @GenIgnore
+  <T> T getLocal(ContextKey<T> key, AccessMode accessMode);
+
+  /**
+   * Get some local data from the context, when it does not exist the {@code initialValueSupplier} is called to obtain
+   * the initial value.
+   *
+   * <p> The {@code initialValueSupplier} might be called multiple times when multiple threads call this method concurrently.
+   *
+   * @param key  the key of the data
+   * @param initialValueSupplier the supplier of the initial value optionally called
+   * @param <T>  the type of the data
+   * @return the local data
+   */
+  @GenIgnore
+  <T> T getLocal(ContextKey<T> key, AccessMode accessMode, Supplier<? extends T> initialValueSupplier);
+
+  /**
+   * Put some local data in the context.
+   * <p>
+   * This can be used to share data between different handlers that share a context
+   *
+   * @param key  the key of the data
+   * @param value  the data
+   */
+  @GenIgnore
+  <T> void putLocal(ContextKey<T> key, AccessMode accessMode, T value);
+
+  /**
+   * Remove some local data from the context.
+   *
+   * @param key  the key to remove
+   */
+  @GenIgnore
+  default <T> void removeLocal(ContextKey<T> key, AccessMode accessMode) {
+    putLocal(key, accessMode, null);
   }
 
   /**

src/main/java/io/vertx/core/impl/ContextBase.java

@@ -10,10 +10,9 @@
  */
 package io.vertx.core.impl;
 
-import io.vertx.core.spi.context.ContextKey;
+import io.vertx.core.spi.context.locals.AccessMode;
+import io.vertx.core.spi.context.locals.ContextKey;
 
-import java.lang.invoke.MethodHandles;
-import java.lang.invoke.VarHandle;
 import java.util.function.Supplier;
 
 /**
@@ -23,54 +22,38 @@
  */
 class ContextBase {
 
-  private static final VarHandle LOCALS_UPDATER = MethodHandles.arrayElementVarHandle(Object[].class);
-
   final Object[] locals;
 
   ContextBase(Object[] locals) {
     this.locals = locals;
   }
 
-  public final <T> T getLocal(ContextKey<T> key) {
+  public final <T> T getLocal(ContextKey<T> key, AccessMode accessMode) {
     ContextKeyImpl<T> internalKey = (ContextKeyImpl<T>) key;
     int index = internalKey.index;
     if (index >= locals.length) {
       throw new IllegalArgumentException();
     }
-    Object res = LOCALS_UPDATER.getVolatile(locals, index);
+    Object res = accessMode.get(locals, index);
     return (T) res;
   }
 
-  public final <T> T getLocal(ContextKey<T> key, Supplier<? extends T> initialValueSupplier) {
+  public final <T> T getLocal(ContextKey<T> key, AccessMode accessMode, Supplier<? extends T> initialValueSupplier) {
     ContextKeyImpl<T> internalKey = (ContextKeyImpl<T>) key;
     int index = internalKey.index;
     if (index >= locals.length) {
       throw new IllegalArgumentException("Invalid key index: " + index);
     }
-    Object res;
-    while (true) {
-      res = LOCALS_UPDATER.getVolatile(locals, index);
-      if (res != null) {
-        break;
-      }
-      Object initial = initialValueSupplier.get();
-      if (initial == null) {
-        throw new IllegalStateException();
-      }
-      if (LOCALS_UPDATER.compareAndSet(locals, index, null, initial)) {
-        res = initial;
-        break;
-      }
-    }
+    Object res = accessMode.getOrCreate(locals, index, (Supplier<Object>) initialValueSupplier);
     return (T) res;
   }
 
-  public final <T> void putLocal(ContextKey<T> key, T value) {
+  public final <T> void putLocal(ContextKey<T> key, AccessMode accessMode, T value) {
     ContextKeyImpl<T> internalKey = (ContextKeyImpl<T>) key;
     int index = internalKey.index;
     if (index >= locals.length) {
       throw new IllegalArgumentException();
     }
-    LOCALS_UPDATER.setRelease(locals, index, value);
+    accessMode.put(locals, index, value);
   }
 }

src/main/java/io/vertx/core/impl/ContextImpl.java

@@ -17,12 +17,9 @@
 import io.vertx.core.impl.logging.Logger;
 import io.vertx.core.impl.logging.LoggerFactory;
 import io.vertx.core.json.JsonObject;
-import io.vertx.core.spi.context.ContextKey;
 import io.vertx.core.spi.metrics.PoolMetrics;
 import io.vertx.core.spi.tracing.VertxTracer;
 
-import java.lang.invoke.MethodHandles;
-import java.lang.invoke.VarHandle;
 import java.util.concurrent.*;
 
 /**

src/main/java/io/vertx/core/impl/ContextInternal.java

@@ -17,7 +17,6 @@
 import io.vertx.core.impl.future.PromiseImpl;
 import io.vertx.core.impl.future.PromiseInternal;
 import io.vertx.core.impl.future.SucceededFuture;
-import io.vertx.core.spi.context.ContextKey;
 import io.vertx.core.spi.tracing.VertxTracer;
 
 import java.util.concurrent.Callable;

src/main/java/io/vertx/core/impl/ContextKeyImpl.java

@@ -10,7 +10,7 @@
  */
 package io.vertx.core.impl;
 
-import io.vertx.core.spi.context.ContextKey;
+import io.vertx.core.spi.context.locals.ContextKey;
 
 /**
  * @author <a href="mailto:[email protected]">Julien Viet</a>

src/main/java/io/vertx/core/impl/DuplicatedContext.java

@@ -16,7 +16,6 @@
 import io.vertx.core.Handler;
 import io.vertx.core.ThreadingModel;
 import io.vertx.core.json.JsonObject;
-import io.vertx.core.spi.context.ContextKey;
 import io.vertx.core.spi.tracing.VertxTracer;
 
 import java.util.concurrent.Callable;

src/main/java/io/vertx/core/spi/context/locals/AccessMode.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2011-2024 Contributors to the Eclipse Foundation
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
+ * which is available at https://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
+ */
+package io.vertx.core.spi.context.locals;
+
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.VarHandle;
+import java.util.function.Supplier;
+
+/**
+ * Defines the access mode of a context locals
+ */
+public interface AccessMode {
+
+  /**
+   * This access mode provides concurrent access to context locals with thread safety and atomicity.
+   */
+  AccessMode CONCURRENT = new AccessMode() {
+
+    private final VarHandle LOCALS_UPDATER = MethodHandles.arrayElementVarHandle(Object[].class);
+
+    @Override
+    public Object get(Object[] locals, int idx) {
+      return LOCALS_UPDATER.getVolatile(locals, idx);
+    }
+
+    @Override
+    public void put(Object[] locals, int idx, Object value) {
+      LOCALS_UPDATER.setRelease(locals, idx, value);
+    }
+
+    @Override
+    public Object getOrCreate(Object[] locals, int index, Supplier<Object> initialValueSupplier) {
+      Object res;
+      while (true) {
+        res = LOCALS_UPDATER.getVolatile(locals, index);
+        if (res != null) {
+          break;
+        }
+        Object initial = initialValueSupplier.get();
+        if (initial == null) {
+          throw new IllegalStateException();
+        }
+        if (LOCALS_UPDATER.compareAndSet(locals, index, null, initial)) {
+          res = initial;
+          break;
+        }
+      }
+      return res;
+    }
+  };
+
+  /**
+   * Return the object at index {@code idx} in the {@code locals} array.
+   * @param locals the array
+   * @param idx the index
+   * @return the object at {@code index}
+   */
+  Object get(Object[] locals, int idx);
+
+  /**
+   * Put {@code value} in the {@code locals} array at index {@code idx}
+   * @param locals the array
+   * @param idx the index
+   * @param value the value
+   */
+  void put(Object[] locals, int idx, Object value);
+
+  Object getOrCreate(Object[] locals, int index, Supplier<Object> initialValueSupplier);
+
+}

src/main/java/io/vertx/core/spi/context/ContextKey.java → src/main/java/io/vertx/core/spi/context/locals/ContextKey.java

@@ -8,7 +8,7 @@
  *
  * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
  */
-package io.vertx.core.spi.context;
+package io.vertx.core.spi.context.locals;
 
 import io.vertx.core.impl.ContextKeyImpl;
 

src/test/java/io/vertx/core/ContextTest.java

@@ -14,7 +14,7 @@
 import io.netty.channel.EventLoop;
 import io.vertx.core.impl.*;
 import io.vertx.core.impl.future.PromiseInternal;
-import io.vertx.core.spi.context.ContextKey;
+import io.vertx.core.spi.context.locals.ContextKey;
 import io.vertx.test.core.VertxTestBase;
 import org.junit.Assume;
 import org.junit.Test;

src/test/java/io/vertx/core/FakeContext.java

@@ -10,7 +10,8 @@
 import io.vertx.core.impl.VertxInternal;
 import io.vertx.core.impl.WorkerPool;
 import io.vertx.core.json.JsonObject;
-import io.vertx.core.spi.context.ContextKey;
+import io.vertx.core.spi.context.locals.AccessMode;
+import io.vertx.core.spi.context.locals.ContextKey;
 import io.vertx.core.spi.tracing.VertxTracer;
 
 import java.util.concurrent.Callable;
@@ -117,22 +118,18 @@ public VertxInternal owner() {
 
   @Override
   public <T> void emit(T argument, Handler<T> task) {
-
   }
 
   @Override
   public void execute(Runnable task) {
-
   }
 
   @Override
   public <T> void execute(T argument, Handler<T> task) {
-
   }
 
   @Override
   public void reportException(Throwable t) {
-
   }
 
   @Override
@@ -176,16 +173,17 @@ public CloseFuture closeFuture() {
   }
 
   @Override
-  public <T> T getLocal(ContextKey<T> key) {
+  public <T> T getLocal(ContextKey<T> key, AccessMode accessMode) {
     return null;
   }
 
   @Override
-  public <T> void putLocal(ContextKey<T> key, T value) {
+  public <T> T getLocal(ContextKey<T> key, AccessMode accessMode, Supplier<? extends T> initialValueSupplier) {
+    return null;
   }
 
   @Override
-  public <T> T getLocal(ContextKey<T> key, Supplier<? extends T> initialValueSupplier) {
-    return null;
+  public <T> void putLocal(ContextKey<T> key, AccessMode accessMode, T value) {
+
   }
 }

src/test/java/io/vertx/core/spi/tracing/EventBusTracerTestBase.java

@@ -16,7 +16,7 @@
 import io.vertx.core.eventbus.Message;
 import io.vertx.core.eventbus.ReplyException;
 import io.vertx.core.impl.ContextKeyHelper;
-import io.vertx.core.spi.context.ContextKey;
+import io.vertx.core.spi.context.locals.ContextKey;
 import io.vertx.core.tracing.TracingPolicy;
 import io.vertx.test.core.VertxTestBase;
 import org.junit.Test;

src/test/java/io/vertx/core/spi/tracing/HttpTracerTestBase.java

@@ -18,7 +18,7 @@
 import io.vertx.core.http.RequestOptions;
 import io.vertx.core.impl.ContextInternal;
 import io.vertx.core.impl.ContextKeyHelper;
-import io.vertx.core.spi.context.ContextKey;
+import io.vertx.core.spi.context.locals.ContextKey;
 import io.vertx.core.spi.observability.HttpRequest;
 import io.vertx.core.spi.observability.HttpResponse;
 import io.vertx.core.tracing.TracingPolicy;

src/test/java/io/vertx/it/CustomContextKey.java

@@ -2,7 +2,7 @@
 
 import io.vertx.core.impl.VertxBuilder;
 import io.vertx.core.spi.VertxServiceProvider;
-import io.vertx.core.spi.context.ContextKey;
+import io.vertx.core.spi.context.locals.ContextKey;
 
 public class CustomContextKey implements VertxServiceProvider  {
 

src/test/java/io/vertx/test/faketracer/FakeTracer.java

@@ -14,7 +14,7 @@
 import io.vertx.core.Context;
 import io.vertx.core.Vertx;
 import io.vertx.core.impl.ContextKeyHelper;
-import io.vertx.core.spi.context.ContextKey;
+import io.vertx.core.spi.context.locals.ContextKey;
 import io.vertx.core.spi.tracing.SpanKind;
 import io.vertx.core.spi.tracing.TagExtractor;
 import io.vertx.core.spi.tracing.VertxTracer;