Fix delay calculation in jitter delays #2115

Lettuce now considers overflow states and the previous delay time unit conversion is correct to avoid zero-delays.

Author: mp911de

src/main/java/io/lettuce/core/resource/DecorrelatedJitterDelay.java

@@ -63,7 +63,7 @@ class DecorrelatedJitterDelay extends Delay implements StatefulDelay {
     public Duration createDelay(long attempt) {
         long value = randomBetween(base, Math.max(base, prevDelay * 3));
         Duration delay = applyBounds(Duration.ofNanos(targetTimeUnit.toNanos(value)), lower, upper);
-        prevDelay = delay.toNanos();
+        prevDelay = targetTimeUnit.convert(delay.toNanos(), TimeUnit.NANOSECONDS);
         return delay;
     }
 

src/main/java/io/lettuce/core/resource/Delay.java

@@ -325,7 +325,7 @@ public static Supplier<Delay> decorrelatedJitter(long lower, long upper, long ba
      * @see ThreadLocalRandom#nextLong(long, long)
      */
     protected static long randomBetween(long min, long max) {
-        if (min == max) {
+        if (min >= max) {
             return min;
         }
         return ThreadLocalRandom.current().nextLong(min, max);

src/main/java/io/lettuce/core/resource/ExponentialDelay.java

@@ -91,8 +91,8 @@ protected static long calculatePowerOfTwo(long attempt) {
 
         if (attempt <= 0) { // safeguard against underflow
             return 0L;
-        } else if (attempt >= 64) { // safeguard against overflow in the bitshift operation
-            return Long.MAX_VALUE;
+        } else if (attempt >= 63) { // safeguard against overflow in the bitshift operation
+            return Long.MAX_VALUE - 1;
         } else {
             return 1L << (attempt - 1);
         }

src/main/java/io/lettuce/core/resource/FullJitterDelay.java

@@ -53,7 +53,8 @@ class FullJitterDelay extends ExponentialDelay {
     public Duration createDelay(long attempt) {
 
         long upperTarget = targetTimeUnit.convert(upper.toNanos(), TimeUnit.NANOSECONDS);
-        long temp = Math.min(upperTarget, base * calculatePowerOfTwo(attempt));
+        long upperBase = base * calculatePowerOfTwo(attempt);
+        long temp = Math.min(upperTarget, 0 > upperBase ? upperTarget : upperBase);
         long delay = temp / 2 + randomBetween(0, temp / 2);
         return applyBounds(Duration.ofNanos(targetTimeUnit.toNanos(delay)));
     }