Change default exponential backoff sequence to not start with zero

Recovery delay was a connection recovery feature from day 1 for a reason:

 * In practice connection recovery often won't succeed the first time
   because network failures don't always go away in milliseconds.
 * There's a natural race condition between server state changes
   (cleanup of queues and such) and the operations a recovered connection
   will perform potentially on entities *with the same identifier* (e.g. name)

Initial delay avoids a lot of scenarios that stem from the above
race condition and can waste a lot of time for operators, developers
and the RabbitMQ core team.

References #307.

Author: michaelklishin

src/main/java/com/rabbitmq/client/RecoveryDelayHandler.java

@@ -67,10 +67,10 @@ class ExponentialBackoffDelayHandler implements RecoveryDelayHandler {
         private final List<Long> sequence;
 
         /**
-         * Default Constructor. Uses the fibonacci sequence: {0, 1000, 1000, 2000, 3000, 5000, 8000, 13000, 21000}.
+         * Default Constructor. Uses the following sequence: 2000, 3000, 5000, 8000, 13000, 21000, 34000
          */
         public ExponentialBackoffDelayHandler() {
-            sequence = Arrays.asList(0L, 1000L, 1000L, 2000L, 3000L, 5000L, 8000L, 13000L, 21000L);
+            sequence = Arrays.asList(2000L, 3000L, 5000L, 8000L, 13000L, 21000L, 34000L);
         }
 
         /**
@@ -88,7 +88,8 @@ public ExponentialBackoffDelayHandler(final List<Long> sequence) {
 
         @Override
         public long getDelay(int recoveryAttempts) {
-            return sequence.get(recoveryAttempts >= sequence.size() ? sequence.size() - 1 : recoveryAttempts);
+            int index = recoveryAttempts >= sequence.size() ? sequence.size() - 1 : recoveryAttempts;
+            return sequence.get(index);
         }
     }
-}
+}

src/test/java/com/rabbitmq/client/test/RecoveryDelayHandlerTest.java

@@ -37,23 +37,23 @@ public void testDefaultRecoveryDelayHandler() {
     }
 
     @Test
-    public void testExponentialBackoffDelayHandler_default() {
+    public void testExponentialBackoffDelayHandlerDefaults() {
         final RecoveryDelayHandler handler = new ExponentialBackoffDelayHandler();
-        assertEquals(0, handler.getDelay(0));
-        assertEquals(1000L, handler.getDelay(1));
-        assertEquals(1000L, handler.getDelay(2));
-        assertEquals(2000L, handler.getDelay(3));
-        assertEquals(3000L, handler.getDelay(4));
-        assertEquals(5000L, handler.getDelay(5));
-        assertEquals(8000L, handler.getDelay(6));
-        assertEquals(13000L, handler.getDelay(7));
-        assertEquals(21000L, handler.getDelay(8));
-        assertEquals(21000L, handler.getDelay(9));
-        assertEquals(21000L, handler.getDelay(Integer.MAX_VALUE));
+        assertEquals(2000L, handler.getDelay(0));
+        assertEquals(3000L, handler.getDelay(1));
+        assertEquals(5000L, handler.getDelay(2));
+        assertEquals(8000L, handler.getDelay(3));
+        assertEquals(13000L, handler.getDelay(4));
+        assertEquals(21000L, handler.getDelay(5));
+        assertEquals(34000L, handler.getDelay(6));
+        assertEquals(34000L, handler.getDelay(7));
+        assertEquals(34000L, handler.getDelay(8));
+        assertEquals(34000L, handler.getDelay(9));
+        assertEquals(34000L, handler.getDelay(Integer.MAX_VALUE));
     }
 
     @Test
-    public void testExponentialBackoffDelayHandler_sequence() {
+    public void testExponentialBackoffDelayHandlerSequence() {
         final RecoveryDelayHandler handler = new ExponentialBackoffDelayHandler(Arrays.asList(1L, 2L));
         assertEquals(1, handler.getDelay(0));
         assertEquals(2, handler.getDelay(1));
@@ -62,12 +62,12 @@ public void testExponentialBackoffDelayHandler_sequence() {
     }
 
     @Test(expected=IllegalArgumentException.class)
-    public void testExponentialBackoffDelayHandler_sequence_null() {
+    public void testExponentialBackoffDelayHandlerWithNullSequence() {
         new ExponentialBackoffDelayHandler(null);
     }
 
     @Test(expected=IllegalArgumentException.class)
-    public void testExponentialBackoffDelayHandler_sequence_empty() {
+    public void testExponentialBackoffDelayHandlerWithEmptySequence() {
         new ExponentialBackoffDelayHandler(Collections.<Long>emptyList());
     }
 }