Merge remote-tracking branch 'origin/3.1.x'

spring-cloud-loadbalancer/src/main/java/org/springframework/cloud/loadbalancer/core/RoundRobinLoadBalancer.java

@@ -100,10 +100,9 @@ public class RoundRobinLoadBalancer implements ReactorServiceInstanceLoadBalance
 			return new EmptyResponse();
 		}
 
-		int pos = this.position.incrementAndGet();
-		if (pos < 0) {
-			pos = pos & Integer.MAX_VALUE;
-		}
+		// Ignore the sign bit, this allows pos to loop sequentially from 0 to
+		// Integer.MAX_VALUE
+		int pos = this.position.incrementAndGet() & Integer.MAX_VALUE;
 
 		ServiceInstance instance = instances.get(pos % instances.size());
 

spring-cloud-loadbalancer/src/test/java/org/springframework/cloud/loadbalancer/core/RoundRobinLoadBalancerTest.java

@@ -26,6 +26,7 @@ import org.springframework.cloud.client.ServiceInstance;
 import org.springframework.cloud.loadbalancer.support.SimpleObjectProvider;
 
 import static java.lang.Integer.MAX_VALUE;
+import static java.lang.Integer.MIN_VALUE;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.mock;
@@ -37,7 +38,22 @@ import static org.mockito.Mockito.when;
 class RoundRobinLoadBalancerTest {
 
 	@Test
-	void shouldEnforceOrderWhenPositiveOverflow() {
+	void shouldOrderEnforcedWhenPositive() {
+		assertOrderEnforced(0);
+	}
+
+	@Test
+	void shouldOrderEnforcedWhenNegative() {
+		assertOrderEnforced(MIN_VALUE);
+	}
+
+	@Test
+	void shouldOrderEnforcedWhenPositiveOverflow() {
+		assertOrderEnforced(MAX_VALUE);
+	}
+
+	@SuppressWarnings("all")
+	void assertOrderEnforced(int seed) {
 		List<ServiceInstance> instances = new ArrayList<>();
 		for (int i = 0; i < 10; i++) {
 			ServiceInstance instance = mock(ServiceInstance.class);
@@ -49,11 +65,12 @@ class RoundRobinLoadBalancerTest {
 		when(supplier.get(any())).thenReturn(Flux.just(instances));
 
 		RoundRobinLoadBalancer loadBalancer = new RoundRobinLoadBalancer(new SimpleObjectProvider<>(supplier),
-				"shouldStartFromZeroWhenPositiveOverflow", MAX_VALUE);
+				"shouldStartFromZeroWhenPositiveOverflow", seed);
 
 		for (int i = 0; i < 10; i++) {
+			int instanceId = ((seed + 1 + i) & MAX_VALUE) % instances.size();
 			ServiceInstance chosen = loadBalancer.choose().block().getServer();
-			assertThat(chosen.getInstanceId()).isEqualTo(i + "");
+			assertThat(chosen.getInstanceId()).isEqualTo(instanceId + "");
 		}
 	}