# kafka

**Repository Path**: yintingting/kafka

## Basic Information

- **Project Name**: kafka
- **Description**: kafka示例
- **Primary Language**: Java
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2019-07-22
- **Last Updated**: 2021-10-01

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

1.搭建集群：https://kafka.apache.org/quickstart
  先启动producer，后启动consumer时，发现consumer从当前接收到的消息开始消费，
那怎样使它从1开始消费呢？
 解决 ：properties.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG,"earliest");
2. 异步发送消息
3. 修改consumer的groupId
properties.put(ConsumerConfig.GROUP_ID_CONFIG,"KafkaConsumerDemo1");
发现consumer会把之前生产者发送过的所有消息都再消费一遍
```message receive : woowo
   message receive : 你不是真正的快乐
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```

 4. properties.put(ConsumerConfig.GROUP_ID_CONFIG,"KafkaConsumerDemo2");
    properties.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG,"latest");
    发现consumer没有消费任何消息
    > earliest对于新的groupId,重置offset
    > latest对于新的groupId,直接取已经消费并且提交的最大的offset
 5. 手动确认
         properties.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG,"false");
    如果不手动提交，那么重启consumer还是会消费到消息
 6.自定义partition
    执行命令：bin/kafka-topics.sh --create --bootstrap-server localhost:9092 --replication-factor 3 --partitions 3 --topic topic2
    创建topic2并分成3个分区012
    观察producer发出的msg在哪个分区，consumer接收到的msg也在哪个分区
 7. consumer指定某个partition接收消息
    例子中consumer只能接收到0 partition的msg  
 8. 多个消费者如何消费
    topic2创建了三个分区，启动三个consumer,发现一个consumer接收一个分区的消息