Fix Kafka integration tests to not reuse message ids. (#291)

* Fix Kafka integration tests to not reuse message ids.

* Fix checkstyle.

Author: vjkoskela

src/test/java/com/arpnetworking/metrics/mad/sources/integration/KafkaSourceIT.java

@@ -64,6 +64,7 @@
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.util.stream.Collectors;
 
 /**
@@ -80,6 +81,7 @@ public class KafkaSourceIT {
     private static final Duration POLL_DURATION = Duration.ofSeconds(1);
     private static final int TIMEOUT = 10000;
     private static final int NUM_RECORDS = 500;
+    private static final AtomicInteger RECORD_ID = new AtomicInteger(0);
 
     private Map<String, Object> _consumerProps;
     private KafkaConsumer<Integer, String> _consumer;
@@ -268,7 +270,8 @@ private static void createTopic(final String topicName) throws TimeoutException
     private static List<ProducerRecord<Integer, String>> createProducerRecords(final String topic, final int num) {
         final List<ProducerRecord<Integer, String>> records = new ArrayList<>();
         for (int i = 0; i < num; i++) {
-            records.add(new ProducerRecord<>(topic, i, "value" + i));
+            final int id = RECORD_ID.getAndIncrement();
+            records.add(new ProducerRecord<>(topic, id, "value" + id));
         }
         return records;
     }