Remove thread sticky context feature.

Motivation:

Thread sticky context was introduced in Vert.x 4 in order to maintain callback ordering when submitting tasks from a non vertx thread.

Vert.x 5 introduces the sticky event-loop feature that implements the same idea for shadow contexts.

In addition shadow context references cannot be reasonnably maintained.

Dropping sticky context support does not break the original intent of the feature and brings behavior consistency when deadling with foreign contexts.

Changes:

Drop stick context feature.

vertx-core/src/main/java/io/vertx/core/impl/VertxImpl.java

@@ -170,7 +170,6 @@ private static ThreadFactory virtualThreadFactory() {
   private final Throwable transportUnavailabilityCause;
   private final VertxTracer tracer;
   private final ThreadLocal<WeakReference<EventLoop>> stickyEventLoop = new ThreadLocal<>();
-  private final ThreadLocal<WeakReference<ContextInternal>> stickyContext = new ThreadLocal<>();
   private final boolean disableTCCL;
   private final Boolean useDaemonThread;
 
@@ -521,7 +520,6 @@ public void execute(Runnable command) {
       } else {
         ctx = createEventLoopContext(eventLoop, workerPool, Thread.currentThread().getContextClassLoader());
       }
-      stickyContext.set(new WeakReference<>(ctx));
       return ctx;
     }
   }
@@ -706,10 +704,6 @@ private ContextInternal getContext(Thread thread) {
         return new ShadowContext(this, new EventLoopExecutor(eventLoop), context);
       }
     } else {
-      WeakReference<ContextInternal> ref = stickyContext.get();
-      if (ref != null) {
-        return ref.get();
-      }
       return null;
     }
   }

vertx-core/src/test/java/io/vertx/tests/context/ContextTest.java

@@ -918,9 +918,8 @@ public void testFailedFutureContextPropagation2() {
   }
 
   @Test
-  public void testSticky() {
+  public void testStickiness() {
     Context ctx = vertx.getOrCreateContext();
-    assertSame(ctx, vertx.getOrCreateContext());
     assertSame(((ContextInternal)ctx).nettyEventLoop(), ((ContextInternal)vertx.getOrCreateContext()).nettyEventLoop());
   }
 

vertx-core/src/test/java/io/vertx/tests/context/EventExecutorProviderTest.java

@@ -46,8 +46,6 @@ public void testExecuteTasks() {
     toRun.pop().run();
     assertEquals(1, cnt[0]);
     assertNull(Vertx.currentContext());
-    // Sticky context
-    assertSame(ctx, vertx.getOrCreateContext());
   }
 
   @Test

vertx-core/src/test/java/io/vertx/tests/worker/NamedWorkerPoolTest.java

@@ -128,28 +128,28 @@ public void testUnordered() throws Exception {
   }
 
   @Test
-  public void testUseDifferentExecutorWithSameTaskQueue() throws Exception {
+  public void testUseDifferentExecutorWithSameTaskQueue() {
     int count = 10;
     waitFor(count);
     WorkerExecutor exec = vertx.createSharedWorkerExecutor("vert.x-the-executor");
-    Thread startThread = Thread.currentThread();
-    AtomicReference<Thread> currentThread = new AtomicReference<>();
-    CountDownLatch latch = new CountDownLatch(1);
-    for (int i = 0;i < count;i++) {
-      int val = i;
-      exec.executeBlocking(() -> {
-        Thread current = Thread.currentThread();
-        assertNotSame(startThread, current);
-        if (val == 0) {
-          assertNull(currentThread.getAndSet(current));
-          awaitLatch(latch);
-        } else {
-          assertSame(current, currentThread.get());
-        }
-        return null;
-      }, true).onComplete(onSuccess(v -> complete()));
-      latch.countDown();
-    }
+    vertx.runOnContext(v1 -> {
+      AtomicReference<Thread> currentThread = new AtomicReference<>();
+      CountDownLatch latch = new CountDownLatch(1);
+      for (int i = 0;i < count;i++) {
+        int val = i;
+        exec.executeBlocking(() -> {
+          Thread current = Thread.currentThread();
+          if (val == 0) {
+            assertNull(currentThread.getAndSet(current));
+            awaitLatch(latch);
+          } else {
+            assertSame(current, currentThread.get());
+          }
+          return null;
+        }, true).onComplete(onSuccess(v2 -> complete()));
+        latch.countDown();
+      }
+    });
     await();
   }