kafka---->kafka的使用（一）

　　今天我们来学习一下kafka的简单的使用与配置。世上有可以挽回的和不可挽回的事，而时间经过就是一种不可挽回的事。

kafka的安装配置

一、kafka的使用场景

活动跟踪：网站用户与前端应用程序发生交互，前端应用程序生成用户活动相关的消息

传递消息：应用程序向用户发送通知就是通过传递消息来实现

度量指标和日志记录：应用程序定期把度量指标或者日志消息发布到kafka主题上，可读被监控或者被专门的日志搜索系统(elasticsearch)分析。

提交日志：可以把数据库的更新发布到kafka上，应用程序通过监控事件流来接收数据库的实时更新

流处理：与hadoop里的map和reduce类似，只不过它操作的是实时数据流

二、为什么选择kafka

多个生产者：用来从多个前端系统收集数据，并以统一的格式对外提供数据

多个消费者：多个消费者从一个单独的消息流上读取数据，而且消费者之间互不影响

基于磁盘的数据存储：消息被提交到磁盘，根据设置的保留规则进行保存

伸缩性：对在线集群进行扩展丝毫不影响整体系统的可用性

高性能：在处理大量数据的同时，它还能保证亚秒级别的消息延迟

三、kafka的一些概念

消息与批次：kafka的数据单元被称为消息，它由字节数组组成。批次就是一组消息，这些消息属于同一个主题和分区

模式：像json或者xml消息模式缺乏强类型处理能力。可以使用Avro来消除消息读写操作之间的耦合性

主题与分区：kafka的消息通过主题进行分类，主题就好比数据库的表。主题可以被分成若干个分区，一个分区就是一个提交日志

生产者与消费者：生产者创建消息，消息者读取消息

broker与集群：一个独立的kafka服务器被称为broker，它接收来自于生产者的消息而且为消费者提供服务

四、kafka的安装与配置

这里的安装以及案例都是基于window上的。kafka的运行需要java环境和zookeeper的启动。kafka使用zookeeper保存集群的元数据信息和消费者信息。

kafka的运行需要java环境，java的下载地址：http://www.oracle.com/technetwork/java/javase/downloads/index.html。

zookeeper的安装，下载地址：http://zookeeper.apache.org/releases.html。解压即可使用。

具体的可以参考这篇文章：https://www.w3cschool.cn/apache_kafka/apache_kafka_installation_steps.html

kafka的java使用

现在我们通过java编写生产者与消费者来演示一下kafka的过程。我们的安装目录如下：

这里面的data目录是我们手动创建的，用地记录产生的日志文件。另外需要修改config下面的server.properties文件。修改如下

log.dirs=D:/Apache/apache-kafka/kafka_2.-0.11.0.1/data

一、启动kafka的broker以及创建topic

新建窗口，切换目录：cd  D:\Apache\apache-kafka\kafka_2.11-0.11.0.1\bin\windows。

运行zookeeper-server-start ../../config/zookeeper.properties启动zookeeper。打印日志

[-- ::,] INFO Reading configuration from: ..\..\config\zookeeper.properties (org.apache.zookeeper.server.quorum.QuorumPeerConfig)
[-- ::,] INFO autopurge.snapRetainCount set to  (org.apache.zookeeper.server.DatadirCleanupManager)
[-- ::,] INFO autopurge.purgeInterval set to  (org.apache.zookeeper.server.DatadirCleanupManager)
[-- ::,] INFO Purge task is not scheduled. (org.apache.zookeeper.server.DatadirCleanupManager)
[-- ::,] WARN Either no config or no quorum defined in config, running  in standalone mode (org.apache.zookeeper.server.quorum.QuorumPeerMain)
[-- ::,] INFO Reading configuration from: ..\..\config\zookeeper.properties (org.apache.zookeeper.server.quorum.QuorumPeerConfig)
[-- ::,] INFO Starting server (org.apache.zookeeper.server.ZooKeeperServerMain)
[-- ::,] INFO Server environment:zookeeper.version=3.4.-39d3a4f269333c922ed3db283be479f9deacaa0f, built on // : GMT (org.apache.zookeeper.server.ZooKeeperServer)
[-- ::,] INFO Server environment:host.name=Linux (org.apache.zookeeper.server.ZooKeeperServer)
[-- ::,] INFO Server environment:java.version=1.8.0_152 (org.apache.zookeeper.server.ZooKeeperServer)
[-- ::,] INFO Server environment:java.vendor=Oracle Corporation (org.apache.zookeeper.server.ZooKeeperServer)
[-- ::,] INFO Server environment:java.home=D:\Java\jdk\jdk1..0_152\jre (org.apache.zookeeper.server.ZooKeeperServer)
........

新建窗口，切换目录： cd  D:\Apache\apache-kafka\kafka_2.11-0.11.0.1\bin\windows。

运行kafka-server-start.bat ../../config/server.properties启动kafka。打印日志

[-- ::,] INFO KafkaConfig values:
        advertised.host.name = null
        advertised.listeners = null
        advertised.port = null
        alter.config.policy.class.name = null
        authorizer.class.name =
        auto.create.topics.enable = true
        auto.leader.rebalance.enable = true
        background.threads =
        broker.id =
        broker.id.generation.enable = true
        broker.rack = null
        compression.type = producer
        connections.max.idle.ms =
        controlled.shutdown.enable = true
        controlled.shutdown.max.retries =
        controlled.shutdown.retry.backoff.ms =
        controller.socket.timeout.ms =
        create.topic.policy.class.name = null
        default.replication.factor =
        delete.records.purgatory.purge.interval.requests =
        delete.topic.enable = false
        fetch.purgatory.purge.interval.requests =
        group.initial.rebalance.delay.ms =
        group.max.session.timeout.ms =
        group.min.session.timeout.ms =
        host.name =
        inter.broker.listener.name = null
        inter.broker.protocol.version = 0.11.-IV2
        leader.imbalance.check.interval.seconds =
        leader.imbalance.per.broker.percentage =
        listener.security.protocol.map = SSL:SSL,SASL_PLAINTEXT:SASL_PLAINTEXT,TRACE:TRACE,SASL_SSL:SASL_SSL,PLAINTEXT:PLAINTEXT
        listeners = null
        log.cleaner.backoff.ms =
        log.cleaner.dedupe.buffer.size =
        log.cleaner.delete.retention.ms =
        log.cleaner.enable = true
        log.cleaner.io.buffer.load.factor = 0.9
        log.cleaner.io.buffer.size =
        log.cleaner.io.max.bytes.per.second = 1.7976931348623157E308
        log.cleaner.min.cleanable.ratio = 0.5
        log.cleaner.min.compaction.lag.ms =
        log.cleaner.threads =
        log.cleanup.policy = [delete]
        log.dir = /tmp/kafka-logs
        log.dirs = D:/Apache/apache-kafka/kafka_2.-0.11.0.1/data
        log.flush.interval.messages =
        log.flush.interval.ms = null
        log.flush.offset.checkpoint.interval.ms =
        log.flush.scheduler.interval.ms =
        log.flush.start.offset.checkpoint.interval.ms =
        log.index.interval.bytes =
        log.index.size.max.bytes =
        log.message.format.version = 0.11.-IV2
        log.message.timestamp.difference.max.ms =
        log.message.timestamp.type = CreateTime
        log.preallocate = false
        log.retention.bytes = -
        log.retention.check.interval.ms =
        log.retention.hours =
        log.retention.minutes = null
        log.retention.ms = null
        log.roll.hours =
        log.roll.jitter.hours =
        log.roll.jitter.ms = null
        log.roll.ms = null
        log.segment.bytes =
        log.segment.delete.delay.ms =
        max.connections.per.ip =
        max.connections.per.ip.overrides =
        message.max.bytes =
        metric.reporters = []
        metrics.num.samples =
        metrics.recording.level = INFO
        metrics.sample.window.ms =
        min.insync.replicas =
        num.io.threads =
        num.network.threads =
        num.partitions =
        num.recovery.threads.per.data.dir =
        num.replica.fetchers =
        offset.metadata.max.bytes =
        offsets.commit.required.acks = -
        offsets.commit.timeout.ms =
        offsets.load.buffer.size =
        offsets.retention.check.interval.ms =
        offsets.retention.minutes =
        offsets.topic.compression.codec =
        offsets.topic.num.partitions =
        offsets.topic.replication.factor =
        offsets.topic.segment.bytes =
        port =
        principal.builder.class = class org.apache.kafka.common.security.auth.DefaultPrincipalBuilder
        producer.purgatory.purge.interval.requests =
        queued.max.requests =
        quota.consumer.default =
        quota.producer.default =
        quota.window.num =
        quota.window.size.seconds =
        replica.fetch.backoff.ms =
        replica.fetch.max.bytes =
        replica.fetch.min.bytes =
        replica.fetch.response.max.bytes =
        replica.fetch.wait.max.ms =
        replica.high.watermark.checkpoint.interval.ms =
        replica.lag.time.max.ms =
        replica.socket.receive.buffer.bytes =
        replica.socket.timeout.ms =
        replication.quota.window.num =
        replication.quota.window.size.seconds =
        request.timeout.ms =
        reserved.broker.max.id =
        sasl.enabled.mechanisms = [GSSAPI]
        sasl.kerberos.kinit.cmd = /usr/bin/kinit
        sasl.kerberos.min.time.before.relogin =
        sasl.kerberos.principal.to.local.rules = [DEFAULT]
        sasl.kerberos.service.name = null
        sasl.kerberos.ticket.renew.jitter = 0.05
        sasl.kerberos.ticket.renew.window.factor = 0.8
        sasl.mechanism.inter.broker.protocol = GSSAPI
        security.inter.broker.protocol = PLAINTEXT
        socket.receive.buffer.bytes =
        socket.request.max.bytes =
        socket.send.buffer.bytes =
        ssl.cipher.suites = null
        ssl.client.auth = none
        ssl.enabled.protocols = [TLSv1., TLSv1., TLSv1]
        ssl.endpoint.identification.algorithm = null
        ssl.key.password = null
        ssl.keymanager.algorithm = SunX509
        ssl.keystore.location = null
        ssl.keystore.password = null
        ssl.keystore.type = JKS
        ssl.protocol = TLS
        ssl.provider = null
        ssl.secure.random.implementation = null
        ssl.trustmanager.algorithm = PKIX
        ssl.truststore.location = null
        ssl.truststore.password = null
        ssl.truststore.type = JKS
        transaction.abort.timed.out.transaction.cleanup.interval.ms =
        transaction.max.timeout.ms =
        transaction.remove.expired.transaction.cleanup.interval.ms =
        transaction.state.log.load.buffer.size =
        transaction.state.log.min.isr =
        transaction.state.log.num.partitions =
        transaction.state.log.replication.factor =
        transaction.state.log.segment.bytes =
        transactional.id.expiration.ms =
        unclean.leader.election.enable = false
        zookeeper.connect = localhost:
        zookeeper.connection.timeout.ms =
        zookeeper.session.timeout.ms =
        zookeeper.set.acl = false
        zookeeper.sync.time.ms =
 (kafka.server.KafkaConfig)
[-- ::,] INFO starting (kafka.server.KafkaServer)
[-- ::,] INFO Connecting to zookeeper on localhost: (kafka.server.KafkaServer)
[-- ::,] INFO Starting ZkClient event thread. (org.I0Itec.zkclient.ZkEventThread)
.......

新建窗口，切换目录： cd  D:\Apache\apache-kafka\kafka_2.11-0.11.0.1\bin\windows。

运行kafka-topics.bat --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic test创建topc，名称为test。

Created topic "test".

二、编写我们的java代码

我们使用的maven依赖如下：

<dependency>
    <groupId>org.apache.kafka</groupId>
    <artifactId>kafka-clients</artifactId>
    <version>0.11.0.1</version>
</dependency>

• 消息的发布者：发布10次消息，从0到9。

package com.linux.huhx.firstdemo;

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

import java.util.Properties;

/**
 * @Author: huhx
 * @Date: 2017-11-03 下午 4:41
 */
public class HelloProducer {

    public static void main(String[] args) {
        String topicName = "test";
        Properties props = new Properties();
        //Assign localhost id
        props.put("bootstrap.servers", "localhost:9092");
        //Set acknowledgements for producer requests.
        props.put("acks", "all");
        //If the request fails, the producer can automatically retry,
        props.put("retries", 0);
        //Specify buffer size in config
        props.put("batch.size", 16384);
        //Reduce the no of requests less than 0
        props.put("linger.ms", 1);
        //The buffer.memory controls the total amount of memory available to the producer for buffering.
        props.put("buffer.memory", 33554432);
        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<>(props);

        for (int i = 0; i < 10; i++) {
            producer.send(new ProducerRecord<>(topicName, Integer.toString(i), Integer.toString(i)));
        }
        System.out.println("Message sent successfully");
        producer.close();
    }
}

• 消息的消费者

package com.linux.huhx.firstdemo;

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

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

/**
 * @Author: huhx
 * @Date: 2017-11-03 下午 5:52
 */
public class HelloConsumer {

    public static void main(String[] args) {
        String topicName = "test";
        Properties props = new Properties();

        props.put("bootstrap.servers", "localhost:9092");
        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");
        KafkaConsumer<String, String> consumer = new KafkaConsumer<>(props);

        consumer.subscribe(Arrays.asList(topicName));
        System.out.println("Subscribed to topic " + topicName);
        int i = 0;
        while (true) {
            ConsumerRecords<String, String> records = consumer.poll(100);
            for (ConsumerRecord<String, String> record : records)
                System.out.printf("offset = %d, key = %s, value = %s\n", record.offset(), record.key(), record.value());
        }
    }
}

运行main函数：(HelloProducer --> HelloConsumer --> HelloProducer)。整个过程HelloProducer发布了20条消息，HelloConsumer只接受到后来的10条消息。HelloConsumer的打印日志如下：

offset = , key = , value =
offset = , key = , value =
offset = , key = , value =
offset = , key = , value =
offset = , key = , value =
offset = , key = , value =
offset = , key = , value =
offset = , key = , value =
offset = , key = , value =
offset = , key = , value = 

原因是topic是基于订阅发布的，不是基于队列的。

三、解决远程java生产者向kafka发送消息

修改kakfa/config下面的server.properties文件，添加以下内容：

# ip是运行kafka的主机
advertised.host.name=192.168.1.101 

重新启动zookeeper和kafka，就可以在kafka接受远程producer的消息。

友情链接

• 对于kafka的快速入门，官方文档比较详细：http://kafka.apache.org/quickstart