进过上一篇的引导，相信大家应该都已经安装好了。这次我们就来简单使用一下。

1 创建 topic

像官网上写的那样，我们可以使用 kafka.topics.sh 脚本来创建一个 topic 。不过，前提是我们需要启动zookeeper 和 kafka 服务。

那我们就用官网上例子好了：

[root@master config]# kafka-topics.sh --create --zookeeper localhost:2181 --topic first                                      

Missing required argument "[partitions]"

Option                                   Description                            
------                                   -----------                            
--alter                                  Alter the number of partitions,        
                                           replica assignment, and/or           
                                           configuration for the topic.         
--config <name=value>                    A topic configuration override for the 
                                           topic being created or altered.The   
                                           following is a list of valid         
                                           configurations:                      
                                                cleanup.policy                        
                                                compression.type                      
                                                delete.retention.ms                   
                                                file.delete.delay.ms                  
                                                flush.messages                        
                                                flush.ms                              
                                                follower.replication.throttled.       
                                           replicas                             
                                                index.interval.bytes                  
                                                leader.replication.throttled.replicas 
                                                max.message.bytes                     
                                                message.format.version                
                                                message.timestamp.difference.max.ms   
                                                message.timestamp.type                
                                                min.cleanable.dirty.ratio             
                                                min.compaction.lag.ms                 
                                                min.insync.replicas                   
                                                preallocate                           
                                                retention.bytes                       
                                                retention.ms                          
                                                segment.bytes                         
                                                segment.index.bytes                   
                                                segment.jitter.ms                     
                                                segment.ms                            
                                                unclean.leader.election.enable        
                                         See the Kafka documentation for full   
                                           details on the topic configs.        
--create                                 Create a new topic.                    
--delete                                 Delete a topic                         
--delete-config <name>                   A topic configuration override to be   
                                           removed for an existing topic (see   
                                           the list of configurations under the 
                                           --config option).                    
--describe                               List details for the given topics.     
--disable-rack-aware                     Disable rack aware replica assignment  
--force                                  Suppress console prompts               
--help                                   Print usage information.               
--if-exists                              if set when altering or deleting       
                                           topics, the action will only execute 
                                           if the topic exists                  
--if-not-exists                          if set when creating topics, the       
                                           action will only execute if the      
                                           topic does not already exist         
--list                                   List all available topics.             
--partitions <Integer: # of partitions>  The number of partitions for the topic 
                                           being created or altered (WARNING:   
                                           If partitions are increased for a    
                                           topic that has a key, the partition  
                                           logic or ordering of the messages    
                                           will be affected                     
--replica-assignment                     A list of manual partition-to-broker   
  <broker_id_for_part1_replica1 :          assignments for the topic being      
  broker_id_for_part1_replica2 ,           created or altered.                  
  broker_id_for_part2_replica1 :                                                
  broker_id_for_part2_replica2 , ...>                                           
--replication-factor <Integer:           The replication factor for each        
  replication factor>                      partition in the topic being created.
--topic <topic>                          The topic to be create, alter or       
                                           describe. Can also accept a regular  
                                           expression except for --create option
--topics-with-overrides                  if set when describing topics, only    
                                           show topics that have overridden     
                                           configs                              
--unavailable-partitions                 if set when describing topics, only    
                                           show partitions whose leader is not  
                                           available                            
--under-replicated-partitions            if set when describing topics, only    
                                           show under replicated partitions     
--zookeeper <urls>                       REQUIRED: The connection string for    
                                           the zookeeper connection in the form 
                                           host:port. Multiple URLS can be      
                                           given to allow fail-over.            
[root@master config]# kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic first
Created topic "first".
[root@master config]# 

哈哈，打错一次他就会给你提示，然后你知道这些参数都是什么意思了，我就不赘述了。

这样我们就创建了一个 topic ，我们还可以使用 kafka.topics.sh 这个脚本来查看 topic 的信息：

[root@master config]# kafka-topics.sh --list --zookeeper localhost:2181

first

[root@master config]# kafka-topics.sh --describe --zookeeper localhost:2181 --topic first
Topic:first     PartitionCount:1        ReplicationFactor:1     Configs:
        Topic: first    Partition: 0    Leader: 1       Replicas: 1     Isr: 1
[root@master config]# 

这里显示出来的 0、1指的是我们 kafka 中 broker 的 ID

2 创建 producer

照葫芦画瓢：

[root@master config]# kafka-console-producer.sh

Read data from standard input and publish it to Kafka.

Option                                   Description                            
------                                   -----------                            
--batch-size <Integer: size>             Number of messages to send in a single 
                                           batch if they are not being sent     
                                           synchronously. (default: 200)        
--broker-list <broker-list>              REQUIRED: The broker list string in    
                                           the form HOST1:PORT1,HOST2:PORT2.    
--compression-codec [compression-codec]  The compression codec: either 'none',  
                                           'gzip', 'snappy', or 'lz4'.If        
                                           specified without value, then it     
                                           defaults to 'gzip'                   
--key-serializer <encoder_class>         The class name of the message encoder  
                                           implementation to use for            
                                           serializing keys. (default: kafka.   
                                           serializer.DefaultEncoder)           
--line-reader <reader_class>             The class name of the class to use for 
                                           reading lines from standard in. By   
                                           default each line is read as a       
                                           separate message. (default: kafka.   
                                           tools.                               
                                           ConsoleProducer$LineMessageReader)   
--max-block-ms <Long: max block on       The max time that the producer will    
  send>                                    block for during a send request      
                                           (default: 60000)                     
--max-memory-bytes <Long: total memory   The total memory used by the producer  
  in bytes>                                to buffer records waiting to be sent 
                                           to the server. (default: 33554432)   
--max-partition-memory-bytes <Long:      The buffer size allocated for a        
  memory in bytes per partition>           partition. When records are received 
                                           which are smaller than this size the 
                                           producer will attempt to             
                                           optimistically group them together   
                                           until this size is reached.          
                                           (default: 16384)                     
--message-send-max-retries <Integer>     Brokers can fail receiving the message 
                                           for multiple reasons, and being      
                                           unavailable transiently is just one  
                                           of them. This property specifies the 
                                           number of retires before the         
                                           producer give up and drop this       
                                           message. (default: 3)                
--metadata-expiry-ms <Long: metadata     The period of time in milliseconds     
  expiration interval>                     after which we force a refresh of    
                                           metadata even if we haven't seen any 
                                           leadership changes. (default: 300000)
--old-producer                           Use the old producer implementation.   
--producer-property <producer_prop>      A mechanism to pass user-defined       
                                           properties in the form key=value to  
                                           the producer.                        
--producer.config <config file>          Producer config properties file. Note  
                                           that [producer-property] takes       
                                           precedence over this config.         
--property <prop>                        A mechanism to pass user-defined       
                                           properties in the form key=value to  
                                           the message reader. This allows      
                                           custom configuration for a user-     
                                           defined message reader.              
--queue-enqueuetimeout-ms <Integer:      Timeout for event enqueue (default:    
  queue enqueuetimeout ms>                 2147483647)                          
--queue-size <Integer: queue_size>       If set and the producer is running in  
                                           asynchronous mode, this gives the    
                                           maximum amount of  messages will     
                                           queue awaiting sufficient batch      
                                           size. (default: 10000)               
--request-required-acks <request         The required acks of the producer      
  required acks>                           requests (default: 1)                
--request-timeout-ms <Integer: request   The ack timeout of the producer        
  timeout ms>                              requests. Value must be non-negative 
                                           and non-zero (default: 1500)         
--retry-backoff-ms <Integer>             Before each retry, the producer        
                                           refreshes the metadata of relevant   
                                           topics. Since leader election takes  
                                           a bit of time, this property         
                                           specifies the amount of time that    
                                           the producer waits before refreshing 
                                           the metadata. (default: 100)         
--socket-buffer-size <Integer: size>     The size of the tcp RECV size.         
                                           (default: 102400)                    
--sync                                   If set message send requests to the    
                                           brokers are synchronously, one at a  
                                           time as they arrive.                 
--timeout <Integer: timeout_ms>          If set and the producer is running in  
                                           asynchronous mode, this gives the    
                                           maximum amount of time a message     
                                           will queue awaiting sufficient batch 
                                           size. The value is given in ms.      
                                           (default: 1000)                      
--topic <topic>                          REQUIRED: The topic id to produce      
                                           messages to.                         
--value-serializer <encoder_class>       The class name of the message encoder  
                                           implementation to use for            
                                           serializing values. (default: kafka. 
                                           serializer.DefaultEncoder)           
[root@master config]# kafka-console-producer.sh --broker-list localhost:9092 --topic first
this is a test.

先报错，再看参数什么含义，还是那样，不做赘述。

当命令参数正确执行之后，是没有什么反馈的，它会等待你输入”消息“，然后它会发布给 kafka，交由 kafka 保管，等待消费者进行消费。我们可以使用”Ctrl + C“来停止。
这里我输入了一句话”this is a test.“，这是我们要发布的。

3 创建 consumer

这时候我们会注意到一句话，”If you have each of the above commands running in a different terminal then you should now be able to type messages into the producer terminal and see them appear in the consumer terminal.“ 也就是说，我们如果是在两个终端上创建 producer 和 consumer 的话，我们在 producer 上输入”消息“，我们的 consumer 上会显示出来。我们来试试，重新启动一个终端用来创建 consumer 。

就像图片上显示的那样，我启动了两个。生产者一边生产，消费者一边消费…

你可能会困惑，为什么会显示两个 “Hello World !”，那是因为我为了能截上这张图，搞错了一次，producer 这边是发送了”消息“出去，我的 consumer 也再等待接收，但是它俩不是同一个 topic 。当我把 producer 和 consumer 都停掉之后重新进来就成这样了。

接下来我们使用 API 来写一下，对于安装包里的文档也是够了，打开之后特别的乱，还是看在线的文档吧。

4 API 操作

在这之前，由于我是使用 maven 来构建项目的，我们可以很方便的引入依赖的 jar 包。
新建一个 maven 项目，然后再 pom.xml 中加入：

    <dependency>
        <groupId>org.apache.kafka</groupId>
        <artifactId>kafka-clients</artifactId>
        <version>0.10.1.0</version>
    </dependency>

这样一来就引入了 kafka 依赖的 jar 包。

我们可以先新建一个 producer ：

package com.signal.kafkaTest;

import java.util.Properties;

import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.Producer;
import org.apache.kafka.clients.producer.ProducerRecord;

public class ProducerTest {

    public static void main(String[] args) {
        Properties props = new Properties();
        props.put("bootstrap.servers", "master:9092,master:9093");
        props.put("acks", "all");
        props.put("retries", 0);
        props.put("batch.size", 16384);
        props.put("linger.ms", 1);
        props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
        props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");

        Producer<String,String> producer = new KafkaProducer<String,String>(props);

        for(int i=0;i<100;i++){
            ProducerRecord<String,String> r = new ProducerRecord<String,String>("message","key-"+i,"value-"+i);
            producer.send(r);
        }

        producer.close();
    }

}

这个我是仿照 API 里写的

这里已经非常清楚了^U^，我就偷工减料了。

然后是 consumer ：

package com.signal.kafkaTest;

import java.util.Arrays;
import java.util.Properties;

import org.apache.kafka.clients.consumer.Consumer;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.KafkaConsumer;

public class ConsumerTest {
    public static void main(String[] args) {
        Properties props = new Properties();
        props.put("bootstrap.servers", "master:9092,master:9093");
        props.put("group.id", "test");
        props.put("enable.auto.commit", "true");
        props.put("auto.commit.interval.ms", "1000");
        props.put("session.timeout.ms", "30000");
        props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
        props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");

        Consumer<String,String> consumer = new KafkaConsumer<String,String>(props);
        consumer.subscribe(Arrays.asList("message"));
        while(true){
            ConsumerRecords<String,String> records = consumer.poll(10);
            for(ConsumerRecord<String,String> record : records){
                System.out.println("offset=" + record.offset() + ",--key=" + record.key() + ",--value=" + record.value());
            }
        }
    }
}

然后先运行 producer ，再运行 consumer ，控制台输出如下：

offset=208,--key=key-0,--value=value-0
offset=209,--key=key-1,--value=value-1
offset=210,--key=key-2,--value=value-2
offset=211,--key=key-3,--value=value-3
offset=212,--key=key-4,--value=value-4
offset=213,--key=key-5,--value=value-5
offset=214,--key=key-6,--value=value-6
offset=215,--key=key-7,--value=value-7
offset=216,--key=key-8,--value=value-8
offset=217,--key=key-9,--value=value-9
offset=218,--key=key-10,--value=value-10
(此处省略)...   

这个就是 kafka 的简单使用了，希望大家好好看看文档，都能很快写出来的。