Kafka学习（一）-------- Quickstart

参考官网：http://kafka.apache.org/quickstart

一、下载Kafka

官网下载地址 http://kafka.apache.org/downloads

截至2019年7月8日 最新版本为 2.3.0 2.12为编译的scala版本 2.3.0为kafka版本

• Scala 2.12  - kafka_2.12-2.3.0.tgz (asc, sha512)

  解压
  > tar -xzf kafka_2.12-2.3.0.tgz
  > cd kafka_2.12-2.3.0
  

二、启动服务

要先启动zookeeper kafka内置了一个 也可以不用

> bin/zookeeper-server-start.sh config/zookeeper.properties
[2013-04-22 15:01:37,495] INFO Reading configuration from: config/zookeeper.properties (org.apache.zookeeper.server.quorum.QuorumPeerConfig)
...

> bin/kafka-server-start.sh config/server.properties
[2013-04-22 15:01:47,028] INFO Verifying properties (kafka.utils.VerifiableProperties)
[2013-04-22 15:01:47,051] INFO Property socket.send.buffer.bytes is overridden to 1048576 (kafka.utils.VerifiableProperties)
...

三、创建topic

replication-factor为1   partitions为1
> bin/kafka-topics.sh --create --bootstrap-server localhost:9092 --replication-factor 1 --partitions 1 --topic test
查看topic
> bin/kafka-topics.sh --list --bootstrap-server localhost:9092
test

也可以不创建topic 设置自动创建 当publish的时候

四、发送消息

用command line client 进行测试 一行就是一条消息

> bin/kafka-console-producer.sh --broker-list localhost:9092 --topic test
This is a message
This is another message

五、消费者

command line consumer 可以接收消息

> bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic test --from-beginning
This is a message
This is another message

六、设置多broker集群

单broker没有意思 我们可以设置三个broker

首先为每个broker 复制配置文件

> cp config/server.properties config/server-1.properties
> cp config/server.properties config/server-2.properties

然后编辑

config/server-1.properties:
    broker.id=1
    listeners=PLAINTEXT://:9093
    log.dirs=/tmp/kafka-logs-1
 
config/server-2.properties:
    broker.id=2
    listeners=PLAINTEXT://:9094
    log.dirs=/tmp/kafka-logs-2

broker.id是唯一的 cluster中每一个node的名字 我们在same machine上 所有要设置listeners和log.dirs 以防冲突

建一个topic 一个partitions 三个replication-factor

> bin/kafka-topics.sh --create --bootstrap-server localhost:9092 --replication-factor 3 --partitions 1 --topic my-replicated-topic

用describe看看都是什么情况
> bin/kafka-topics.sh --describe --bootstrap-server localhost:9092 --topic my-replicated-topic
Topic:my-replicated-topic   PartitionCount:1    ReplicationFactor:3 Configs:
    Topic: my-replicated-topic  Partition: 0    Leader: 1   Replicas: 1,2,0 Isr: 1,2,0

• 有几个概念 ：

• "leader" is the node responsible for all reads and writes for the given partition. Each node will be the leader for a randomly selected portion of the partitions.

• "replicas" is the list of nodes that replicate the log for this partition regardless of whether they are the leader or even if they are currently alive.

• "isr" is the set of "in-sync" replicas. This is the subset of the replicas list that is currently alive and caught-up to the leader.

  ​

刚才那个topic
> bin/kafka-topics.sh --describe --bootstrap-server localhost:9092 --topic test
Topic:test  PartitionCount:1    ReplicationFactor:1 Configs:
    Topic: test Partition: 0    Leader: 0   Replicas: 0 Isr: 0

发送 接收

> bin/kafka-console-producer.sh --broker-list localhost:9092 --topic my-replicated-topic
...
my test message 1
my test message 2
^C


> bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --from-beginning --topic my-replicated-topic
...
my test message 1
my test message 2
^C

试一下容错 fault-tolerance

> ps aux | grep server-1.properties
7564 ttys002    0:15.91 /System/Library/Frameworks/JavaVM.framework/Versions/1.8/Home/bin/java...
> kill -9 7564

看一下变化：Leader换了一个  因为1被干掉了
> bin/kafka-topics.sh --describe --bootstrap-server localhost:9092 --topic my-replicated-topic
Topic:my-replicated-topic   PartitionCount:1    ReplicationFactor:3 Configs:
    Topic: my-replicated-topic  Partition: 0    Leader: 2   Replicas: 1,2,0 Isr: 2,0

还是收到了消息
> bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --from-beginning --topic my-replicated-topic
...
my test message 1
my test message 2
^C

七、使用kafka import/export data

刚才都是console 的数据，其他的sources other systems呢 用Kafka Connect

弄一个数据
> echo -e "foo
bar" > test.txt

启动  指定配置文件
> bin/connect-standalone.sh config/connect-standalone.properties config/connect-file-source.properties config/connect-file-sink.properties

验证一下
> more test.sink.txt
foo
bar

消费者端
> bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic connect-test --from-beginning
{"schema":{"type":"string","optional":false},"payload":"foo"}
{"schema":{"type":"string","optional":false},"payload":"bar"}
...

可以继续写入
> echo Another line>> test.txt

八、使用Kafka Streams

http://kafka.apache.org/22/documentation/streams/quickstart

WordCountDemo

https://github.com/apache/kafka/blob/2.2/streams/examples/src/main/java/org/apache/kafka/streams/examples/wordcount/WordCountDemo.java

代码片段

// Serializers/deserializers (serde) for String and Long types
final Serde<String> stringSerde = Serdes.String();
final Serde<Long> longSerde = Serdes.Long();
 
// Construct a `KStream` from the input topic "streams-plaintext-input", where message values
// represent lines of text (for the sake of this example, we ignore whatever may be stored
// in the message keys).
KStream<String, String> textLines = builder.stream("streams-plaintext-input",
    Consumed.with(stringSerde, stringSerde);
 
KTable<String, Long> wordCounts = textLines
    // Split each text line, by whitespace, into words.
    .flatMapValues(value -> Arrays.asList(value.toLowerCase().split("\W+")))
 
    // Group the text words as message keys
    .groupBy((key, value) -> value)
 
    // Count the occurrences of each word (message key).
    .count()
 
// Store the running counts as a changelog stream to the output topic.
wordCounts.toStream().to("streams-wordcount-output", Produced.with(Serdes.String(), Serdes.Long()));

建一个 Kafka producer 指定input topic output topic

> bin/kafka-topics.sh --create 
    --bootstrap-server localhost:9092 
    --replication-factor 1 
    --partitions 1 
    --topic streams-wordcount-output 
    --config cleanup.policy=compact
Created topic "streams-wordcount-output".

启动WordCount demo application

bin/kafka-run-class.sh org.apache.kafka.streams.examples.wordcount.WordCountDemo

启动一个生产者写数据

> bin/kafka-console-producer.sh --broker-list localhost:9092 --topic streams-plaintext-input
all streams lead to kafka
hello kafka streams

启动一个消费者接数据

> bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 
    --topic streams-wordcount-output 
    --from-beginning 
    --formatter kafka.tools.DefaultMessageFormatter 
    --property print.key=true 
    --property print.value=true 
    --property key.deserializer=org.apache.kafka.common.serialization.StringDeserializer 
    --property value.deserializer=org.apache.kafka.common.serialization.LongDeserializer
    
all     1
streams 1
lead    1
to      1
kafka   1
hello   1
kafka   2
streams 2
kafka   1