Kafka Sink Connector crashes with OOM

I have been trying to setup MongoDB Sink Connector and the connector crashes with below OOM. I have tried increasing the Heap Opts to 2g and it has no fruitful result.

Message size on the topic is very small and the batch size is 1.

WorkerSinkTask{id=test-0} Task threw an uncaught and unrecoverable exception"
java.lang.OutOfMemoryError: Java heap space
        at java.nio.HeapByteBuffer.<init>(HeapByteBuffer.java:57)
        at java.nio.ByteBuffer.allocate(ByteBuffer.java:335)
        at org.apache.kafka.common.memory.MemoryPool$1.tryAllocate(MemoryPool.java:30)
        at org.apache.kafka.common.network.NetworkReceive.readFrom(NetworkReceive.java:112)
        at org.apache.kafka.common.network.KafkaChannel.receive(KafkaChannel.java:424)
        at org.apache.kafka.common.network.KafkaChannel.read(KafkaChannel.java:385)
        at org.apache.kafka.common.network.Selector.attemptRead(Selector.java:651)
        at org.apache.kafka.common.network.Selector.pollSelectionKeys(Selector.java:572)
        at org.apache.kafka.common.network.Selector.poll(Selector.java:483)
        at org.apache.kafka.clients.NetworkClient.poll(NetworkClient.java:547)
        at org.apache.kafka.clients.consumer.internals.ConsumerNetworkClient.poll(ConsumerNetworkClient.java:262)
        at org.apache.kafka.clients.consumer.internals.ConsumerNetworkClient.poll(ConsumerNetworkClient.java:233)
        at org.apache.kafka.clients.consumer.internals.ConsumerNetworkClient.poll(ConsumerNetworkClient.java:212)
        at org.apache.kafka.clients.consumer.internals.AbstractCoordinator.ensureCoordinatorReady(AbstractCoordinator.java:230)
        at org.apache.kafka.clients.consumer.internals.ConsumerCoordinator.poll(ConsumerCoordinator.java:444)
        at org.apache.kafka.clients.consumer.KafkaConsumer.updateAssignmentMetadataIfNeeded(KafkaConsumer.java:1267)
        at org.apache.kafka.clients.consumer.KafkaConsumer.poll(KafkaConsumer.java:1231)
        at org.apache.kafka.clients.consumer.KafkaConsumer.poll(KafkaConsumer.java:1211)
        at org.apache.kafka.connect.runtime.WorkerSinkTask.pollConsumer(WorkerSinkTask.java:444)
        at org.apache.kafka.connect.runtime.WorkerSinkTask.poll(WorkerSinkTask.java:317)
        at org.apache.kafka.connect.runtime.WorkerSinkTask.iteration(WorkerSinkTask.java:224)
        at org.apache.kafka.connect.runtime.WorkerSinkTask.execute(WorkerSinkTask.java:192)
        at org.apache.kafka.connect.runtime.WorkerTask.doRun(WorkerTask.java:177)
        at org.apache.kafka.connect.runtime.WorkerTask.run(WorkerTask.java:227)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)