Kafka学习

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\nbar" > 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 stringSerde = Serdes.String();
final Serde 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