minimal impl

core/src/main/java/com/linecorp/armeria/internal/common/CancellationScheduler.java

@@ -62,6 +62,9 @@ public final class CancellationScheduler {
     private static final AtomicLongFieldUpdater<CancellationScheduler> pendingTimeoutNanosUpdater =
             AtomicLongFieldUpdater.newUpdater(CancellationScheduler.class, "pendingTimeoutNanos");
 
+    private static final AtomicLongFieldUpdater<CancellationScheduler> initializeTriggeredUpdater =
+            AtomicLongFieldUpdater.newUpdater(CancellationScheduler.class, "initializeTriggered");
+
     private static final Runnable noopPendingTask = () -> {
     };
 
@@ -86,6 +89,7 @@ public final class CancellationScheduler {
     private volatile TimeoutFuture whenTimedOut;
     @SuppressWarnings("FieldMayBeFinal")
     private volatile long pendingTimeoutNanos;
+    private volatile long initializeTriggered;
     private boolean server;
     @Nullable
     private Throwable cause;
@@ -99,6 +103,10 @@ public CancellationScheduler(long timeoutNanos) {
      * Initializes this {@link CancellationScheduler}.
      */
     public void init(EventExecutor eventLoop, CancellationTask task, long timeoutNanos, boolean server) {
+        if (!initializeTriggeredUpdater.compareAndSet(this, 0, 1)) {
+            // already cancelled or initialized
+            return;
+        }
         if (!eventLoop.inEventLoop()) {
             eventLoop.execute(() -> init0(eventLoop, task, timeoutNanos, server));
         } else {
@@ -301,6 +309,15 @@ public void finishNow(@Nullable Throwable cause) {
         if (isFinishing()) {
             return;
         }
+
+        if (initializeTriggeredUpdater.compareAndSet(this, 0, 1)) {
+            // finish immediately since init hasn't been called yet
+            state = State.FINISHED;
+            this.cause = cause;
+            ((CancellationFuture) whenCancelled()).doComplete(cause);
+            return;
+        }
+
         if (isInitialized()) {
             if (eventLoop.inEventLoop()) {
                 finishNow0(cause);