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Java Client

apache kafka-client

官方文档：https://kafka.apache.org/11/documentation.html#producerapi

官方java doc: https://kafka.apache.org/11/javadoc/overview-summary.html

Kafka Tutorial: Writing a Kafka Producer in Java

Kafka Producer配置解读

Example: Simple Producer Demo

pom.xml

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<!-- https://mvnrepository.com/artifact/org.apache.kafka/kafka-clients -->
<dependency>
    <groupId>org.apache.kafka</groupId>
    <artifactId>kafka-clients</artifactId>
    <version>2.1.1</version>
</dependency>
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public class KafkaProducerExample {
    // ...
    private static Producer<Long, String> createProducer() {
        Properties props = new Properties();
        // ProducerConfig: https://kafka.apache.org/11/javadoc/index.html?org/apache/kafka/clients/producer/ProducerConfig.html
        props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG,
                                            BOOTSTRAP_SERVERS);
        props.put(ProducerConfig.CLIENT_ID_CONFIG, "KafkaExampleProducer");
        props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG,
                                        LongSerializer.class.getName());
        props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG,
                                    StringSerializer.class.getName());
        
        // KafkaProducer： https://kafka.apache.org/11/javadoc/org/apache/kafka/clients/producer/KafkaProducer.html
        return new KafkaProducer<>(props);
    }

   static void runProducer(final int sendMessageCount) throws Exception {
      final Producer<Long, String> producer = createProducer();
      long time = System.currentTimeMillis();

      try {
          for (long index = time; index < time + sendMessageCount; index++) {
              final ProducerRecord<Long, String> record =
                      new ProducerRecord<>(TOPIC, index,
                                  "Hello Mom " + index);

              RecordMetadata metadata = producer.send(record).get();

              long elapsedTime = System.currentTimeMillis() - time;
              System.out.printf("sent record(key=%s value=%s) " +
                              "meta(partition=%d, offset=%d) time=%d\n",
                      record.key(), record.value(), metadata.partition(),
                      metadata.offset(), elapsedTime);

          }
      } finally {
          producer.flush();
          producer.close();
      }
  }

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Shell

Logic

for

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for file in ./*
do
    if test -f $file
    then
        echo $file is file
    fi
    if test -d $file
    then
        echo $file is dictionary
    fi
done

Network

DNS

DNS刷新缓存

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service nscd restart
service dnsmasq restart
rndc restart

查看某个record 何时才能失效,假设你的默认dns server 不是authoritative server

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dig +nocmd +noall +answer www.google.com

查看某个record 从authoritative server 请求一个record 时被设置的ttl

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dig @ns1.google.com +nocmd www.google.com +noall +answer

Proxy

/etc/profile

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export http_proxy=xxx
export https_proxy=xxx

tc

See linux 下使用 tc 模拟网络延迟和丢包

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# 将 eth0 网卡的传输设置为延迟 100 毫秒发送
tc qdisc add dev eth0 root netem delay 100ms
# 删除上面配置
tc qdisc del dev eth0 root netem delay 100ms

Common

Date & Time

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# date +%Y%m%d
20190613

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Introduction

The new major version of the programmer-friendly testing framework for Java

官网：https://junit.org/junit5/

User Guide: https://junit.org/junit5/docs/current/user-guide/#overview

Getting Started

https://github.com/junit-team/junit5-samples/tree/r5.4.2/junit5-jupiter-starter-maven

pom.xml

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<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    
    <!-- omit -->

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter</artifactId>
            <version>5.4.2</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <pluginManagement>
            <plugins>
                <plugin>
                    <artifactId>maven-surefire-plugin</artifactId>
                    <version>2.22.1</version>
                </plugin>
            </plugins>
        </pluginManagement>
    </build>
</project>

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Cluster

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kubectl cluster-info
kubectl get nodes