[tests] Increase robustness of SimpleRecoveryITCase

flink-tests/src/test/java/org/apache/flink/test/recovery/SimpleRecoveryITCase.java

@@ -199,7 +199,7 @@ public class SimpleRecoveryITCase {
 					"localhost", cluster.getJobManagerRPCPort());
 
 			env.setParallelism(4);
-			env.setNumberOfExecutionRetries(3);
+			env.setNumberOfExecutionRetries(5);
 
 			env.generateSequence(1, 10)
 					.rebalance()
@@ -238,7 +238,7 @@ public class SimpleRecoveryITCase {
 
 	private static class FailingMapper1<T> extends RichMapFunction<T, T> {
 
-		private static int failuresBeforeSuccess = 1;
+		private static volatile int failuresBeforeSuccess = 1;
 
 		@Override
 		public T map(T value) throws Exception {
@@ -253,7 +253,7 @@ public class SimpleRecoveryITCase {
 
 	private static class FailingMapper2<T> extends RichMapFunction<T, T> {
 
-		private static int failuresBeforeSuccess = 1;
+		private static volatile int failuresBeforeSuccess = 1;
 
 		@Override
 		public T map(T value) throws Exception {
@@ -268,7 +268,7 @@ public class SimpleRecoveryITCase {
 
 	private static class FailingMapper3<T> extends RichMapFunction<T, T> {
 
-		private static int failuresBeforeSuccess = 3;
+		private static volatile int failuresBeforeSuccess = 3;
 
 		@Override
 		public T map(T value) throws Exception {