why my kafka has message in one partition?

Question

I have two kafka brokers with two partitions on local machine, and use the following tool to write one local file into kafka test2 topic.

# create topic
  ./kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 2 --partitions 2 --topic test2
  Created topic "test2".
  # write 15MB file to kafka, very fast!!
  kafka-console-producer.sh --broker-list localhost:9093,localhost:9094 --topic test2 < data.txt
  # read data from kafka
  ./kafka-console-consumer.sh --zookeeper localhost:2181 --topic test2 --from-beginning

Then I find all messages are in one partition, how to debug this?

$ kafka-run-class.sh kafka.tools.GetOffsetShell --broker-list localhost:9093,localhost:9094 --topic test2 --time -1
    SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
    SLF4J: Defaulting to no-operation (NOP) logger implementation
    SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
    test2:0:68263
    test2:1:0

The status of partition is:

$ kafka-topics.sh --describe --zookeeper localhost:2181 --topic test2
Topic:test2 PartitionCount:2    ReplicationFactor:2 Configs:
    Topic: test2    Partition: 0    Leader: 1   Replicas: 1,2   Isr: 1,2
    Topic: test2    Partition: 1    Leader: 2   Replicas: 2,1   Isr: 2,1

Answer 1

I will try the following:

1. Use kcat(formerly kafkacat tool, makes producing/consumer significantly easier)
2. Try publishing 10s of messages
3. Try publishing message with key, have observed key with null were getting published to single partition