Reimplement the local context map with context keys

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

@@ -44,7 +44,6 @@ public final class ContextImpl extends ContextBase implements ContextInternal {
   private final EventLoop eventLoop;
   private final EventExecutor executor;
   private ConcurrentMap<Object, Object> data;
-  private ConcurrentMap<Object, Object> localData;
   private volatile Handler<Throwable> exceptionHandler;
   final TaskQueue internalOrderedTasks;
   final WorkerPool internalWorkerPool;
@@ -213,14 +212,6 @@ public synchronized ConcurrentMap<Object, Object> contextData() {
     return data;
   }
 
-  @Override
-  public synchronized ConcurrentMap<Object, Object> localContextData() {
-    if (localData == null) {
-      localData = new ConcurrentHashMap<>();
-    }
-    return localData;
-  }
-
   public void reportException(Throwable t) {
     Handler<Throwable> handler = exceptionHandler;
     if (handler == null) {

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

@@ -14,6 +14,7 @@
 import io.netty.channel.EventLoop;
 import io.vertx.codegen.annotations.GenIgnore;
 import io.vertx.core.*;
+import io.vertx.core.Future;
 import io.vertx.core.impl.future.FailedFuture;
 import io.vertx.core.impl.future.PromiseImpl;
 import io.vertx.core.impl.future.PromiseInternal;
@@ -22,10 +23,7 @@
 import io.vertx.core.spi.context.locals.ContextKey;
 import io.vertx.core.spi.tracing.VertxTracer;
 
-import java.util.concurrent.Callable;
-import java.util.concurrent.ConcurrentMap;
-import java.util.concurrent.Executor;
-import java.util.concurrent.TimeUnit;
+import java.util.concurrent.*;
 import java.util.function.Supplier;
 
 /**
@@ -37,6 +35,8 @@
  */
 public interface ContextInternal extends Context {
 
+  ContextKey<ConcurrentMap<Object, Object>> LOCAL_MAP = new ContextKeyImpl<>(0);
+
   /**
    * @return the current context
    */
@@ -308,7 +308,9 @@ default boolean remove(Object key) {
   /**
    * @return the {@link ConcurrentMap} used to store local context data
    */
-  ConcurrentMap<Object, Object> localContextData();
+  default ConcurrentMap<Object, Object> localContextData() {
+    return getLocal(LOCAL_MAP, ConcurrentHashMap::new);
+  }
 
   /**
    * Get some local data from the context.

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

@@ -17,8 +17,13 @@
  */
 public class ContextKeyImpl<T> implements ContextKey<T> {
 
-  final int index = KeySeq.next();
+  final int index;
+
+  public ContextKeyImpl(int index) {
+    this.index = index;
+  }
 
   public ContextKeyImpl() {
+    this.index = KeySeq.next();
   }
 }

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

@@ -36,8 +36,7 @@
  */
 final class DuplicatedContext extends ContextBase implements ContextInternal {
 
-  protected final ContextImpl delegate;
-  private ConcurrentMap<Object, Object> localData;
+  final ContextImpl delegate;
 
   DuplicatedContext(ContextImpl delegate, Object[] locals) {
     super(locals);
@@ -120,16 +119,6 @@ public final ConcurrentMap<Object, Object> contextData() {
     return delegate.contextData();
   }
 
-  @Override
-  public final ConcurrentMap<Object, Object> localContextData() {
-    synchronized (this) {
-      if (localData == null) {
-        localData = new ConcurrentHashMap<>();
-      }
-      return localData;
-    }
-  }
-
   @Override
   public <T> Future<T> executeBlockingInternal(Callable<T> action) {
     return ContextImpl.executeBlocking(this, action, delegate.internalWorkerPool, delegate.internalOrderedTasks);

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

@@ -17,13 +17,14 @@
  */
 class KeySeq {
 
+  // 0 : reserved slot for local context map
   private static final AtomicInteger seq = new AtomicInteger();
 
   /**
    * Hook for testing purposes
    */
   static void reset() {
-    seq.set((0));
+    seq.set((1));
   }
 
   static int get() {

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

@@ -137,11 +137,6 @@ public ConcurrentMap<Object, Object> contextData() {
     return null;
   }
 
-  @Override
-  public ConcurrentMap<Object, Object> localContextData() {
-    return null;
-  }
-
   @Override
   public ClassLoader classLoader() {
     return tccl;