I took a look at ./flink-connectors/flink-connector-kafka-0.9/src/main/java/org/apache/flink/streaming/connectors/kafka/internal/Kafka09Fetcher.java
It seems the List subscribedPartitionStates was being modified when runFetchLoop iterated the List. This can happen if, e.g., FlinkKafkaConsumer runs the following code concurrently: kafkaFetcher.addDiscoveredPartitions(discoveredPartitions); You can log a JIRA. If you have unit test reproducing this, that would be great. FYI On Fri, May 11, 2018 at 5:15 PM, Vishal Santoshi <vishal.santo...@gmail.com> wrote: > java.util.ConcurrentModificationException > at > java.util.LinkedList$ListItr.checkForComodification(LinkedList.java:966) > at java.util.LinkedList$ListItr.next(LinkedList.java:888) > at > org.apache.flink.streaming.connectors.kafka.internal.Kafka09Fetcher.runFetchLoop(Kafka09Fetcher.java:134) > > . > > . > > . > > > > This flink 1.4.0 > > Any ideas folks ? >