Flink读取数据的5种方式（文件，Socket，Kafka，MySQL，自定义数据源）

从文件中读取数据

这是最简单的数据读取方式。当需要进行功能测试时，可以将数据保存在文件中，读取后验证流处理的逻辑是否符合预期。

程序代码：

package cn.jihui.flink

import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment

object readFile {
  def main(args: Array[String]): Unit = {
    val env = StreamExecutionEnvironment.getExecutionEnvironment

    val file_name = "C:\\Users\\32985\\IdeaProjects\\flink_demo1\\resources\\wc.txt"

    val streamData = env.readTextFile(file_name)

    streamData.print

    env.execute("read data from file")
  }
}

输出结果

"C:\Program Files\Java\jdk-11\bin\java.exe" "-javaagent:D:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2019.3.3\lib\idea_rt.jar=61478:D:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2019.3.3\bin" -Dfile.encoding=UTF-8 -classpath C:\Users\32985\IdeaProjects\flink_demo1\out\production\flink_demo1;D:\Bigdata\scala-2.12.18\lib\scala-library.jar;D:\Bigdata\scala-2.12.18\lib\scala-parser-combinators_2.12-1.0.7.jar;D:\Bigdata\scala-2.12.18\lib\scala-reflect.jar;D:\Bigdata\scala-2.12.18\lib\scala-swing_2.12-2.0.3.jar;D:\Bigdata\scala-2.12.18\lib\scala-xml_2.12-2.1.0.jar;D:\Bigdata\flink-1.10.1\lib\log4j-1.2.17.jar;D:\Bigdata\flink-1.10.1\lib\slf4j-log4j12-1.7.15.jar;D:\Bigdata\flink-1.10.1\lib\flink-dist_2.12-1.10.1.jar;D:\Bigdata\flink-1.10.1\lib\flink-table_2.12-1.10.1.jar;D:\Bigdata\flink-1.10.1\lib\flink-table-blink_2.12-1.10.1.jar cn.jihui.flink.readFile
log4j:WARN No appenders could be found for logger (org.apache.flink.api.java.typeutils.TypeExtractor).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.apache.flink.api.java.ClosureCleaner (file:/D:/Bigdata/flink-1.10.1/lib/flink-dist_2.12-1.10.1.jar) to field java.lang.String.value
WARNING: Please consider reporting this to the maintainers of org.apache.flink.api.java.ClosureCleaner
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
2> hello world
3> how are you
5> I am fine
7> how old are you

Process finished with exit code 0

从Socket中读取数据

用于验证一些通过Socket传输数据的场景非常方便。

程序代码：

package cn.jihui.flink

import org.apache.flink.streaming.api.scala.StreamExecutionEnvironment

object readSocket {
  def main(args: Array[String]): Unit = {
    val env = StreamExecutionEnvironment.getExecutionEnvironment

    val ip = "172.16.3.6"
    val port = 9999

    val streamData = env.socketTextStream(ip, port)

    streamData.print

    env.execute("read data from socket")
  }
}

测试时，需要先在172.16.3.6的服务器上启动nc，然后再启动Flink读取数据。如

[bigdata@vm6 ~]$ nc -lk 9999
hello world
how are you  
happy new year

在nc每输入一行数据，在Flink上均可接收到该行数据。

Flink输出内容如下：

"C:\Program Files\Java\jdk-11\bin\java.exe" "-javaagent:D:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2019.3.3\lib\idea_rt.jar=61731:D:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2019.3.3\bin" -Dfile.encoding=UTF-8 -classpath C:\Users\32985\IdeaProjects\flink_demo1\out\production\flink_demo1;D:\Bigdata\scala-2.12.18\lib\scala-library.jar;D:\Bigdata\scala-2.12.18\lib\scala-parser-combinators_2.12-1.0.7.jar;D:\Bigdata\scala-2.12.18\lib\scala-reflect.jar;D:\Bigdata\scala-2.12.18\lib\scala-swing_2.12-2.0.3.jar;D:\Bigdata\scala-2.12.18\lib\scala-xml_2.12-2.1.0.jar;D:\Bigdata\flink-1.10.1\lib\log4j-1.2.17.jar;D:\Bigdata\flink-1.10.1\lib\slf4j-log4j12-1.7.15.jar;D:\Bigdata\flink-1.10.1\lib\flink-dist_2.12-1.10.1.jar;D:\Bigdata\flink-1.10.1\lib\flink-table_2.12-1.10.1.jar;D:\Bigdata\flink-1.10.1\lib\flink-table-blink_2.12-1.10.1.jar cn.jihui.flink.readSocket
log4j:WARN No appenders could be found for logger (org.apache.flink.api.java.ClosureCleaner).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.apache.flink.api.java.ClosureCleaner (file:/D:/Bigdata/flink-1.10.1/lib/flink-dist_2.12-1.10.1.jar) to field java.lang.String.value
WARNING: Please consider reporting this to the maintainers of org.apache.flink.api.java.ClosureCleaner
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
3> hello world
4> how are you
5> happy new year

从Kafka中读取数据

从Kafka中读取数据，可能是Flink应用最广泛的一种方式。目前我的客户也使用这种方式进行流数据的处理。

从Kafka中读取数据，可以使用flink-connector-kafka。

创建一个Maven工程，加入下面的依赖：

    org.apache.flink
    flink-connector-kafka-0.11_2.12
    1.10.2

程序代码：

package cn.jihui.flink

import java.util.Properties

import org.apache.flink.api.common.serialization.SimpleStringSchema
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment
import org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumer011

object readKafka {
  def main(args: Array[String]): Unit = {
    val env = StreamExecutionEnvironment.getExecutionEnvironment

    val properties = new Properties()
    properties.setProperty("bootstrap.servers", "172.16.3.6:9092")
    properties.setProperty("group.id", "data-group")

    val streamData = env.addSource(new FlinkKafkaConsumer011[String]("sensor", new SimpleStringSchema, properties))

    streamData.print()
    env.execute()
  }
}

启动Kafka

[bigdata@vm6 kafka-2.6.0]$ ./bin/kafka-server-start.sh -daemon config/server.properties

查看是否成功

[bigdata@vm6 ~]$ jps
8690 QuorumPeerMain
21068 Jps
10366 Kafka
[bigdata@vm6 ~]$

启动Kafka的测试脚本

[bigdata@vm6 bin]$ ./kafka-console-producer.sh --broker-list 172.16.3.6:9092 --topic sensor
>hello world
>happy new year
>what are you doing here?   
>

当在Kafka的测试脚本中输入文本时，启动Flink程序可以接收到数据，并进行输出。

输出结果

"C:\Program Files\Java\jdk-11\bin\java.exe" "-javaagent:D:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2019.3.3\lib\idea_rt.jar=60325:D:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2019.3.3\bin" -Dfile.encoding=UTF-8 -classpath C:\Users\32985\IdeaProjects\flink_demo\target\classes;C:\Users\32985\.m2\repository\org\apache\flink\flink-scala_2.12\1.10.1\flink-scala_2.12-1.10.1.jar;C:\Users\32985\.m2\repository\org\apache\flink\flink-core\1.10.1\flink-core-1.10.1.jar;C:\Users\32985\.m2\repository\org\apache\flink\flink-annotations\1.10.1\flink-annotations-1.10.1.jar;C:
......
:\Users\32985\.m2\repository\net\jpountz\lz4\lz4\1.3.0\lz4-1.3.0.jar;C:\Users\32985\.m2\repository\org\xerial\snappy\snappy-java\1.1.2.6\snappy-java-1.1.2.6.jar;C:\Users\32985\.m2\repository\mysql\mysql-connector-java\5.1.46\mysql-connector-java-5.1.46.jar;D:\Bigdata\scala-2.12.18\lib\scala-library.jar;D:\Bigdata\scala-2.12.18\lib\scala-parser-combinators_2.12-1.0.7.jar;D:\Bigdata\scala-2.12.18\lib\scala-reflect.jar;D:\Bigdata\scala-2.12.18\lib\scala-swing_2.12-2.0.3.jar;D:\Bigdata\scala-2.12.18\lib\scala-xml_2.12-2.1.0.jar cn.jihui.flink.readKafka
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.apache.flink.api.java.ClosureCleaner (file:/C:/Users/32985/.m2/repository/org/apache/flink/flink-core/1.10.1/flink-core-1.10.1.jar) to field java.lang.String.value
WARNING: Please consider reporting this to the maintainers of org.apache.flink.api.java.ClosureCleaner
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
7> hello world
7> happy new year
7> what are you doing here?

Process finished with exit code -1

从MySQL中读取数据

当需要从关系数据库中读取数据时，可以简单的JDBC方式进行读取。

程序代码：

package cn.jihui.flink

import java.sql.{DriverManager, ResultSet}

import org.apache.flink.streaming.api.functions.source.{RichSourceFunction, SourceFunction}
import org.apache.flink.streaming.api.scala.StreamExecutionEnvironment
import org.apache.flink.streaming.api.scala._

//case class SensorReading(id: String, timestamp: Long, temperature: Double)

object readMySQL {
  def main(args: Array[String]): Unit = {
    val env = StreamExecutionEnvironment.getExecutionEnvironment
    val streamData = env.addSource(new MySQLSource)
    streamData.print()
    env.execute("read data from mysql")
  }
}

class MySQLSource extends SourceFunction[SensorReading] {
  var running: Boolean = true;

  override def run(sourceContext: SourceFunction.SourceContext[SensorReading]): Unit = {
    val strConn = "jdbc:mysql://172.16.3.6:3306/flink"
    val conn = DriverManager.getConnection(strConn, "jihui", "111111")
    val selectStmt = conn.prepareStatement("select * from t_sensor;")

    val resultRs: ResultSet = selectStmt.executeQuery()

    while (resultRs.next()) {
      if (running) {
        val id = resultRs.getString(1)
        val timestamp = resultRs.getLong(2)
        val temperature = resultRs.getDouble(3)

        sourceContext.collect(SensorReading(id, timestamp, temperature))
      }
    }

    resultRs.close()
    selectStmt.close()
    conn.close()
  }

  override def cancel(): Unit = {
    running = false
  }
}

输出内容：

"C:\Program Files\Java\jdk-11\bin\java.exe" "-javaagent:D:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2019.3.3\lib\idea_rt.jar=61886:D:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2019.3.3\bin" -Dfile.encoding=UTF-8 -classpath 
......
C:\Users\32985\.m2\repository\org\apache\kafka\kafka-clients\0.11.0.2\kafka-clients-0.11.0.2.jar;C:\Users\32985\.m2\repository\net\jpountz\lz4\lz4\1.3.0\lz4-1.3.0.jar;C:\Users\32985\.m2\repository\org\xerial\snappy\snappy-java\1.1.2.6\snappy-java-1.1.2.6.jar;C:\Users\32985\.m2\repository\mysql\mysql-connector-java\5.1.46\mysql-connector-java-5.1.46.jar;D:\Bigdata\scala-2.12.18\lib\scala-library.jar;D:\Bigdata\scala-2.12.18\lib\scala-parser-combinators_2.12-1.0.7.jar;D:\Bigdata\scala-2.12.18\lib\scala-reflect.jar;D:\Bigdata\scala-2.12.18\lib\scala-swing_2.12-2.0.3.jar;D:\Bigdata\scala-2.12.18\lib\scala-xml_2.12-2.1.0.jar cn.jihui.flink.readMySQL
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.apache.flink.api.java.ClosureCleaner (file:/C:/Users/32985/.m2/repository/org/apache/flink/flink-core/1.10.1/flink-core-1.10.1.jar) to field java.lang.String.value
WARNING: Please consider reporting this to the maintainers of org.apache.flink.api.java.ClosureCleaner
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
7> SensorReading(Sensor_4,1687944878278,42.6205)
1> SensorReading(Sensor_10,1687944879294,31.3545)
7> SensorReading(Sensor_7,1687944878278,16.3773)
1> SensorReading(Sensor_4,1687944879294,42.6205)
7> SensorReading(Sensor_8,1687944879294,7.3655)
7> SensorReading(Sensor_2,1687944878278,32.3747)
8> SensorReading(Sensor_1,1687944879294,20.0778)
8> SensorReading(Sensor_9,1687944878278,7.65736)
5> SensorReading(Sensor_3,1687944878278,32.9043)
6> SensorReading(Sensor_1,1687944880296,20.0778)
5> SensorReading(Sensor_10,1687944880296,31.3545)
2> SensorReading(Sensor_8,1687944880296,7.3655)
6> SensorReading(Sensor_6,1687944878278,4.37994)
2> SensorReading(Sensor_5,1687944880296,42.1028)
2> SensorReading(Sensor_2,1687944880296,32.3747)
4> SensorReading(Sensor_10,1687944878278,31.3545)
4> SensorReading(Sensor_9,1687944879294,7.65736)
4> SensorReading(Sensor_9,1687944880296,7.65736)
5> SensorReading(Sensor_2,1687944879294,32.3747)
5> SensorReading(Sensor_6,1687944879294,4.37994)
3> SensorReading(Sensor_5,1687944879294,42.1028)
4> SensorReading(Sensor_7,1687944879294,16.3773)
6> SensorReading(Sensor_5,1687944878278,42.1028)
8> SensorReading(Sensor_8,1687944878278,7.3655)
1> SensorReading(Sensor_4,1687944880296,42.6205)
6> SensorReading(Sensor_3,1687944879294,32.9043)
3> SensorReading(Sensor_7,1687944880296,16.3773)
8> SensorReading(Sensor_6,1687944880296,4.37994)
3> SensorReading(Sensor_3,1687944880296,32.9043)
3> SensorReading(Sensor_1,1687944878278,20.0778)

Process finished with exit code 0

从自定义数据源读取数据

当需要对Flink进行一些性能测试时，可以使用自定义数据源来简化测试过程。

Flink支持自定义数据源，可以使用循环生成所需要格式的测试数据，使用方式非常灵活。

程序代码：

package cn.jihui.flink

import java.util.Random

import org.apache.flink.streaming.api.functions.source.SourceFunction
import org.apache.flink.streaming.api.scala.StreamExecutionEnvironment
import org.apache.flink.streaming.api.scala._

case class SensorReading(id: String, timestamp: Long, temperature: Double)

object readCustom {
  def main(args: Array[String]): Unit = {
    val env = StreamExecutionEnvironment.getExecutionEnvironment

    val dataCustom = env.addSource(new MySensorSource())

    dataCustom.print()

    env.execute("custom data source")
  }
}

class MySensorSource extends SourceFunction[SensorReading] {
  var running: Boolean = true

  override def run(sourceContext: SourceFunction.SourceContext[SensorReading]): Unit = {
    val rand = new Random()

    var currTemp = 1.to(10).map(i => ("Sensor_" + i, rand.nextDouble() * 50))

    while(running) {
      val currTime = System.currentTimeMillis()

      currTemp.map(
        data => (data._1, data._2 + rand.nextGaussian())
      )

      currTemp.foreach(
        data => sourceContext.collect(SensorReading(data._1, currTime, data._2))
      )
    }
  }

  override def cancel(): Unit = running = false
}

运行程序后，会产生源源不断的数据。

输出内容：

"C:\Program Files\Java\jdk-11\bin\java.exe" "-javaagent:D:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2019.3.3\lib\idea_rt.jar=62739:D:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2019.3.3\bin" -Dfile.encoding=UTF-8 -classpath C:\Users\32985\IdeaProjects\flink_demo1\out\production\flink_demo1;D:\Bigdata\scala-2.12.18\lib\scala-library.jar;D:\Bigdata\scala-2.12.18\lib\scala-parser-combinators_2.12-1.0.7.jar;D:\Bigdata\scala-2.12.18\lib\scala-reflect.jar;D:\Bigdata\scala-2.12.18\lib\scala-swing_2.12-2.0.3.jar;D:\Bigdata\scala-2.12.18\lib\scala-xml_2.12-2.1.0.jar;D:\Bigdata\flink-1.10.1\lib\log4j-1.2.17.jar;D:\Bigdata\flink-1.10.1\lib\slf4j-log4j12-1.7.15.jar;D:\Bigdata\flink-1.10.1\lib\flink-dist_2.12-1.10.1.jar;D:\Bigdata\flink-1.10.1\lib\flink-table_2.12-1.10.1.jar;D:\Bigdata\flink-1.10.1\lib\flink-table-blink_2.12-1.10.1.jar cn.jihui.flink.readCustom
log4j:WARN No appenders could be found for logger (org.apache.flink.api.scala.ClosureCleaner$).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.apache.flink.api.java.ClosureCleaner (file:/D:/Bigdata/flink-1.10.1/lib/flink-dist_2.12-1.10.1.jar) to field java.lang.String.value
WARNING: Please consider reporting this to the maintainers of org.apache.flink.api.java.ClosureCleaner
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
7> SensorReading(Sensor_4,1687944878278,42.62052120270371)
1> SensorReading(Sensor_6,1687944878278,4.3799399141547735)
3> SensorReading(Sensor_8,1687944878278,7.365503979569099)
5> SensorReading(Sensor_2,1687944878278,32.374658798648426)
6> SensorReading(Sensor_3,1687944878278,32.9042516066123)
2> SensorReading(Sensor_7,1687944878278,16.37730093567341)
8> SensorReading(Sensor_5,1687944878278,42.1027668775983)
4> SensorReading(Sensor_1,1687944878278,20.077801500835886)
5> SensorReading(Sensor_10,1687944878278,31.35446091105863)
4> SensorReading(Sensor_9,1687944878278,7.657356771011931)
5> SensorReading(Sensor_8,1687944879294,7.365503979569099)
3> SensorReading(Sensor_6,1687944879294,4.3799399141547735)
6> SensorReading(Sensor_1,1687944879294,20.077801500835886)
1> SensorReading(Sensor_4,1687944879294,42.62052120270371)
4> SensorReading(Sensor_7,1687944879294,16.37730093567341)
2> SensorReading(Sensor_5,1687944879294,42.1027668775983)
6> SensorReading(Sensor_9,1687944879294,7.657356771011931)
7> SensorReading(Sensor_2,1687944879294,32.374658798648426)
8> SensorReading(Sensor_3,1687944879294,32.9042516066123)
7> SensorReading(Sensor_10,1687944879294,31.35446091105863)
4> SensorReading(Sensor_5,1687944880296,42.1027668775983)
1> SensorReading(Sensor_2,1687944880296,32.374658798648426)
5> SensorReading(Sensor_6,1687944880296,4.3799399141547735)
7> SensorReading(Sensor_8,1687944880296,7.365503979569099)
6> SensorReading(Sensor_7,1687944880296,16.37730093567341)
2> SensorReading(Sensor_3,1687944880296,32.9042516066123)
3> SensorReading(Sensor_4,1687944880296,42.62052120270371)
8> SensorReading(Sensor_1,1687944880296,20.077801500835886)
1> SensorReading(Sensor_10,1687944880296,31.35446091105863)
8> SensorReading(Sensor_9,1687944880296,7.657356771011931)

Process finished with exit code -1