Merge pull request #869 from akka/wip-2686-HWT-overflow-∂π

make HashedWheelTimer tolerate wrap-arounds, see #2686

akka-actor-tests/src/test/scala/akka/util/DurationSpec.scala

@@ -8,10 +8,31 @@ import language.postfixOps
 import org.scalatest.WordSpec
 import org.scalatest.matchers.MustMatchers
 import scala.concurrent.duration._
+import scala.concurrent.Await
 
 import java.util.concurrent.TimeUnit._
+import akka.testkit.AkkaSpec
+import akka.testkit.TestLatch
+import java.util.concurrent.TimeoutException
+import akka.testkit.LongRunningTest
 
-class DurationSpec extends WordSpec with MustMatchers {
+class DurationSpec extends AkkaSpec {
+
+  "A HashedWheelTimer" must {
+
+    "not mess up long timeouts" taggedAs LongRunningTest in {
+      val longish = Long.MaxValue.nanos
+      val barrier = TestLatch()
+      import system.dispatcher
+      val job = system.scheduler.scheduleOnce(longish)(barrier.countDown())
+      intercept[TimeoutException] {
+        // this used to fire after 46 seconds due to wrap-around
+        Await.ready(barrier, 90 seconds)
+      }
+      job.cancel()
+    }
+
+  }
 
   "Duration" must {
 

akka-actor/src/main/java/akka/util/internal/HashedWheelTimer.java

@@ -263,8 +263,11 @@ public class HashedWheelTimer implements Timer {
 
     void scheduleTimeout(HashedWheelTimeout timeout, long delay) {
         // Prepare the required parameters to schedule the timeout object.
-        final long relativeIndex = Math.max(1, (delay + tickDuration - 1) / tickDuration); // If relative index < 1 then it should be 1
-
+        long relativeIndex = (delay + tickDuration - 1) / tickDuration;
+        // if the previous line had an overflow going on, then we’ll just schedule this timeout
+        // one tick early; that shouldn’t matter since we’re talking 270 years here
+        if (relativeIndex < 0) relativeIndex = delay / tickDuration;
+        if (relativeIndex == 0) relativeIndex = 1;
         final long remainingRounds = relativeIndex / wheel.length;
 
         // Add the timeout to the wheel.
@@ -304,7 +307,7 @@ public class HashedWheelTimer implements Timer {
 
             while (!shutdown()) {
                 final long deadline = waitForNextTick();
-                if (deadline > 0)
+                if (deadline > Long.MIN_VALUE)
                     notifyExpiredTimeouts(fetchExpiredTimeouts(deadline));
             }
         }
@@ -332,7 +335,7 @@ public class HashedWheelTimer implements Timer {
                 HashedWheelTimeout timeout = i.next();
                 if (timeout.remainingRounds <= 0) {
                     i.remove();
-                    if (timeout.deadline <= deadline) {
+                    if (timeout.deadline - deadline <= 0) {
                         expiredTimeouts.add(timeout);
                     } else {
                         // Handle the case where the timeout is put into a wrong
@@ -368,6 +371,12 @@ public class HashedWheelTimer implements Timer {
             expiredTimeouts.clear();
         }
 
+        /**
+         * calculate goal nanoTime from startTime and current tick number,
+         * then wait until that goal has been reached.
+         * 
+         * @return Long.MIN_VALUE if received a shutdown request, current time otherwise (with Long.MIN_VALUE changed by +1)
+         */
         private long waitForNextTick() {
             long deadline = startTime + tickDuration * tick;
 
@@ -378,7 +387,8 @@ public class HashedWheelTimer implements Timer {
 
                 if (sleepTimeMs <= 0) {
                     tick += 1;
-                    return currentTime;
+                    if (currentTime == Long.MIN_VALUE) return -Long.MAX_VALUE;
+                    else return currentTime;
                 }
 
                 // Check if we run on windows, as if thats the case we will need
@@ -394,7 +404,7 @@ public class HashedWheelTimer implements Timer {
                     Thread.sleep(sleepTimeMs);
                 } catch (InterruptedException e) {
                     if (shutdown()) {
-                        return -1;
+                        return Long.MIN_VALUE;
                     }
                 }
             }