From bbf50844329b330ca4eb8198de6c43ea1b2a0451 Mon Sep 17 00:00:00 2001
From: yipk <yipk@fenqi.im>
Date: Mon, 5 Dec 2016 13:46:44 +0800
Subject: [PATCH 1/2] AtomicInteger.incrementAndGet() is likely overflow 
 AtomicInteger(Integer.MAX_VALUE).incrementAndGet() returns -2147483648

---
 .../loadbalancer/AbstractServerPredicate.java | 20 +++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/ribbon-loadbalancer/src/main/java/com/netflix/loadbalancer/AbstractServerPredicate.java b/ribbon-loadbalancer/src/main/java/com/netflix/loadbalancer/AbstractServerPredicate.java
index 62186a62..408f6431 100644
--- a/ribbon-loadbalancer/src/main/java/com/netflix/loadbalancer/AbstractServerPredicate.java
+++ b/ribbon-loadbalancer/src/main/java/com/netflix/loadbalancer/AbstractServerPredicate.java
@@ -137,6 +137,22 @@ public List<Server> getEligibleServers(List<Server> servers, Object loadBalancer
             return results;            
         }
     }
+	
+	/**
+	 * Referenced from RoundRobinRule
+     * Inspired by the implementation of {@link AtomicInteger#incrementAndGet()}.
+     *
+     * @param modulo The modulo to bound the value of the counter.
+     * @return The next value.
+     */
+    private int incrementAndGetModulo(int modulo) {
+        for (;;) {
+            int current = nextIndex.get();
+            int next = (current + 1) % modulo;
+            if (nextIndex.compareAndSet(current, next))
+                return next;
+        }
+    }
     
     /**
      * Choose a random server after the predicate filters a list of servers. Load balancer key 
@@ -160,7 +176,7 @@ public Optional<Server> chooseRoundRobinAfterFiltering(List<Server> servers) {
         if (eligible.size() == 0) {
             return Optional.absent();
         }
-        return Optional.of(eligible.get(nextIndex.getAndIncrement() % eligible.size()));
+        return Optional.of(eligible.get(incrementAndGetModulo(eligible.size())));
     }
     
     /**
@@ -184,7 +200,7 @@ public Optional<Server> chooseRoundRobinAfterFiltering(List<Server> servers, Obj
         if (eligible.size() == 0) {
             return Optional.absent();
         }
-        return Optional.of(eligible.get(nextIndex.getAndIncrement() % eligible.size()));
+        return Optional.of(eligible.get(incrementAndGetModulo(eligible.size())));
     }
         
     /**

From 53a2c7dc6dbd94959510f4a2e697657b276ab0f7 Mon Sep 17 00:00:00 2001
From: yipk <yipk@fenqi.im>
Date: Tue, 6 Dec 2016 18:37:40 +0800
Subject: [PATCH 2/2] change to return current to make unit test pass

---
 .../java/com/netflix/loadbalancer/AbstractServerPredicate.java  | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ribbon-loadbalancer/src/main/java/com/netflix/loadbalancer/AbstractServerPredicate.java b/ribbon-loadbalancer/src/main/java/com/netflix/loadbalancer/AbstractServerPredicate.java
index 408f6431..c4bc11ca 100644
--- a/ribbon-loadbalancer/src/main/java/com/netflix/loadbalancer/AbstractServerPredicate.java
+++ b/ribbon-loadbalancer/src/main/java/com/netflix/loadbalancer/AbstractServerPredicate.java
@@ -150,7 +150,7 @@ private int incrementAndGetModulo(int modulo) {
             int current = nextIndex.get();
             int next = (current + 1) % modulo;
             if (nextIndex.compareAndSet(current, next))
-                return next;
+                return current;
         }
     }