title: Kafka reassignment of __consumer_offsets incorrect?
body: <p>I am confused with how kafka-reassignment-paritions works for __consumer_offsets topic?</p>
  
  <p>I start with 1 zk and 1 kafka broker, create a test topic with replication=1, partition=1. consume and produce. works fine.</p>
  
  <p>I see __consumer_offsets topic created. </p>
  
  <p>Now I add a second broker with, <strong>offsets.topic.replication.factor=2</strong>.
  I run the, </p>
  
  <p><strong>kafka-reassign-partitions --zookeeper zookeeper1:2181 --topics-to-move-json-file topics-to-move.json --broker-list "101,102" --generate</strong> </p>
  
  <p>The generated reassignment does not look right. Only shows one replica even though there are 2 live brokers.</p>
  
  <p>I was hoping to get following replicas for each partition: 
  [101, 102] or [201, 101]</p>
  
  <pre><code>{
    "version": 1,
    "partitions": [
      {
        "topic": "__consumer_offsets",
        "partition": 19,
        "replicas": [101]
      },
      {
        "topic": "__consumer_offsets",
        "partition": 30,
        "replicas": [102]
      },
      {
        "topic": "__consumer_offsets",
        "partition": 47,
        "replicas": [101]
      }, ...
  </code></pre>
  
  <p>Appreciate any suggestion.</p>
  
  <p>-Vms</p>