Learning Apache Flink(API)

本文是参考Apache Flink v1.3官方文档，本文所使用的是scala版本的API，基础架构参见《Learning Apache Flink(BASIC)》

业务场景

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Flink接kafka的数据，然后通过初步的过滤得到一个结果集，再进行“打标签”，最后对“打标签”的结果进行过滤，最终输出到kafka中。例如，在topic foo中的数据表示"imsi,lac,cell"，先通过imsi字段筛选出所有以460开头的字段，再通过lac和cell字段判断是否在指定的区域，增加一个字段isSpecifiedLocation，值为true或者false。最终输出到kafka中的字段为"imsi,lac,cell,isSpecifiedLocation,timestamp"，且isSpecifiedLocation为true。

Flink读kafka数据

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注：本文中所使用的kafka的版本为0.10.0
官方文档中Provided TableSources针对kafka指提供了json和avro格式的接入，所以如果是在topic中的数据是csv格式的，可以模仿Kafka010JsonTableSource和JsonRowDeserializationSchema自定义KafkaCsvTableSource和CsvRowDeserializationSchema解析csv格式数据(具体实现参见完整代码章节)，然后就可以通过下面的方法注册一个TableSource

//Register a TableSource
val kafkaTableSource = new KafkaCsvTableSource(
      "foo",
      properties,
      new CsvRowDeserializationSchema(typeInfo),
      typeInfo)

tableEnv.registerTableSource("KafkaCsvTable", kafkaTableSource)
val kafkaCsvTable = tableEnv.scan("KafkaCsvTable")

得到一个Table之后，就可以使用Table API，进行数据的过滤

val filterResult = kafkaCsvTable.where('imsi like "460%").select("imsi,lac,cell")

DataStream动态增加字段

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1. 将Table转换为DataStream

val dsRow: DataStream[Row] = tableEnv.toAppendStream(filterResult)

2. 增加字段

val newDsRows = dsRow.map(row => {
  val ret = new Row(row.getArity() + 2)

  for(i <- 0 to row.getArity()-1) {
    ret.setField(i, row.getField(i))
  }

  val isSpecifiedLocation = if(ret.getField(1).equals(ret.getField(2))) true else false
  ret.setField(row.getArity(), isSpecifiedLocation)

  ret.setField(row.getArity()+1, System.currentTimeMillis())

  ret
})

3. 再将新生成的DataStream注册为Table，进行最终的过滤

 tableEnv.registerDataStream("newTable", newDsRows)
 val newKafkaCsvTable = tableEnv.scan("newTable")
 val newResult = newKafkaCsvTable.filter('isSpecifiedLocation === true).select("imsi,lac,cell,isSpecifiedLocation,timestamp")

Flink向kafka写数据

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本文使用的是Flink提供的Kafka09JsonTableSink类直接将结果输出为json格式

 val sink = new Kafka09JsonTableSink("bar", properties, new FlinkFixedPartitioner[Row])
 newResult.writeToSink(sink)

测试用例

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1. 执行./bin/flink run -c com.woople.streaming.scala.examples.kafka.FlinkKafkaDemo /opt/flink-tutorials-1.0-bundle.jar

2. 向topic foo中写入4601234,1,1数据，在topic bar中可以得到{"imsi":"4601234","lac":"1","cell":"1","isSpecifiedLocation":true,"timestamp":1511222771896}结果，如果输入的是4601234,2,1则不符合条件不会输出。

Troubleshooting

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在代码调试过程中遇到一个错误

org.apache.flink.table.api.TableException: An input of GenericTypeInfo<Row> cannot be converted to Table. Please specify the type of the input with a RowTypeInfo.

在网上找到FLINK-6500，参考里面的方法，在代码中添加了这行代码之后，问题解决了

implicit val tpe: TypeInformation[Row] = new RowTypeInfo(types, names)

完整代码

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pom.xml

<?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">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.woople</groupId>
    <artifactId>flink-tutorials</artifactId>
    <version>1.0</version>

    <dependencies>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-streaming-scala_2.11</artifactId>
            <version>1.3.2</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-connector-kafka-0.10_2.11</artifactId>
            <version>1.3.2</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-table_2.10</artifactId>
            <version>1.3.2</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-scala_2.10</artifactId>
            <version>1.3.2</version>
        </dependency>
    </dependencies>
    
    <build>
        <defaultGoal>package</defaultGoal>

        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-resources-plugin</artifactId>
                <configuration>
                    <encoding>UTF-8</encoding>
                </configuration>
                <executions>
                    <execution>
                        <goals>
                            <goal>copy-resources</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>net.alchim31.maven</groupId>
                <artifactId>scala-maven-plugin</artifactId>
                <version>3.2.2</version>
                <executions>
                    <execution>
                        <id>eclipse-add-source</id>
                        <goals>
                            <goal>add-source</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>scala-compile-first</id>
                        <phase>process-resources</phase>
                        <goals>
                            <goal>compile</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>scala-test-compile-first</id>
                        <phase>process-test-resources</phase>
                        <goals>
                            <goal>testCompile</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>attach-scaladocs</id>
                        <phase>verify</phase>
                        <goals>
                            <goal>doc-jar</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <scalaVersion>2.11.8</scalaVersion>
                    <recompileMode>incremental</recompileMode>
                    <useZincServer>true</useZincServer>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.5.1</version>
                <executions>
                    <execution>
                        <phase>compile</phase>
                        <goals>
                            <goal>compile</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <source>1.6</source>
                    <target>1.6</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>2.4.1</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <shadedArtifactAttached>false</shadedArtifactAttached>
                    <filters>
                        <filter>
                            <artifact>*:*</artifact>
                            <excludes>
                                <exclude>META-INF/*.SF</exclude>
                                <exclude>META-INF/*.DSA</exclude>
                                <exclude>META-INF/*.RSA</exclude>
                            </excludes>
                        </filter>
                    </filters>
                    <finalName>${project.artifactId}-${project.version}-bundle</finalName>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

KafkaCsvTableSource.java

package com.woople.flink.streaming.connectors.kafka;
import org.apache.flink.api.common.typeinfo.TypeInformation;
import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumer010;
import org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumerBase;
import org.apache.flink.streaming.util.serialization.DeserializationSchema;
import org.apache.flink.table.sources.StreamTableSource;
import org.apache.flink.types.Row;
import org.apache.flink.util.Preconditions;
import java.util.Properties;

public class KafkaCsvTableSource implements StreamTableSource<Row> {
    /** The Kafka topic to consume. */
    private final String topic;

    /** Properties for the Kafka consumer. */
    private final Properties properties;

    /** Deserialization schema to use for Kafka records. */
    private final DeserializationSchema<Row> deserializationSchema;

    /** Type information describing the result type. */
    private final TypeInformation<Row> typeInfo;

    /**
     * Creates a generic Kafka {@link StreamTableSource}.
     *
     * @param topic                 Kafka topic to consume.
     * @param properties            Properties for the Kafka consumer.
     * @param deserializationSchema Deserialization schema to use for Kafka records.
     * @param typeInfo              Type information describing the result type.
     */
    public KafkaCsvTableSource(
            String topic,
            Properties properties,
            DeserializationSchema<Row> deserializationSchema,
            TypeInformation<Row> typeInfo) {

        this.topic = Preconditions.checkNotNull(topic, "Topic");
        this.properties = Preconditions.checkNotNull(properties, "Properties");
        this.deserializationSchema = Preconditions.checkNotNull(deserializationSchema, "Deserialization schema");
        this.typeInfo = Preconditions.checkNotNull(typeInfo, "Type information");
    }

    /**
     * NOTE: This method is for internal use only for defining a TableSource.
     *       Do not use it in Table API programs.
     */
    @Override
    public DataStream<Row> getDataStream(StreamExecutionEnvironment env) {
        // Version-specific Kafka consumer
        FlinkKafkaConsumerBase<Row> kafkaConsumer = getKafkaConsumer(topic, properties, deserializationSchema);
        return env.addSource(kafkaConsumer);
    }

    @Override
    public TypeInformation<Row> getReturnType() {
        return typeInfo;
    }

    /**
     * Returns the version-specific Kafka consumer.
     *
     * @param topic                 Kafka topic to consume.
     * @param properties            Properties for the Kafka consumer.
     * @param deserializationSchema Deserialization schema to use for Kafka records.
     * @return The version-specific Kafka consumer
     */
    private FlinkKafkaConsumerBase<Row> getKafkaConsumer(String topic, Properties properties, DeserializationSchema<Row> deserializationSchema) {
        return new FlinkKafkaConsumer010<Row>(topic, deserializationSchema, properties);
    }
    /**
     * Returns the deserialization schema.
     *
     * @return The deserialization schema
     */
    protected DeserializationSchema<Row> getDeserializationSchema() {
        return deserializationSchema;
    }

    @Override
    public String explainSource() {
        return "";
    }
}

CsvRowDeserializationSchema.java

package com.woople.flink.streaming.connectors.kafka;
import org.apache.flink.api.common.typeinfo.TypeInformation;
import org.apache.flink.api.java.typeutils.RowTypeInfo;
import org.apache.flink.streaming.util.serialization.DeserializationSchema;
import org.apache.flink.types.Row;
import org.apache.flink.util.Preconditions;

import java.io.IOException;

public class CsvRowDeserializationSchema implements DeserializationSchema<Row> {
    /** Type information describing the result type. */
    private final TypeInformation<Row> typeInfo;

    /** Field names to parse. Indices match fieldTypes indices. */
    private final String[] fieldNames;

    /** Types to parse fields as. Indices match fieldNames indices. */
    private final TypeInformation<?>[] fieldTypes;

    /** Flag indicating whether to fail on a missing field. */
    private boolean failOnMissingField;

    /**
     * Creates a JSON deserialization schema for the given fields and types.
     *
     * @param typeInfo   Type information describing the result type. The field names are used
     *                   to parse the JSON file and so are the types.
     */
    public CsvRowDeserializationSchema(TypeInformation<Row> typeInfo) {
        Preconditions.checkNotNull(typeInfo, "Type information");
        this.typeInfo = typeInfo;

        this.fieldNames = ((RowTypeInfo) typeInfo).getFieldNames();
        this.fieldTypes = ((RowTypeInfo) typeInfo).getFieldTypes();
    }

    @Override
    public Row deserialize(byte[] message) throws IOException {
        try {
            String messages = new String(message);
            String[] messagesArray = messages.split(",");

            Row row = new Row(fieldNames.length);
            for (int i = 0; i < fieldNames.length; i++) {
                row.setField(i, messagesArray[i]);
            }

            return row;
        } catch (Throwable t) {
            throw new IOException("Failed to deserialize JSON object.", t);
        }
    }

    @Override
    public boolean isEndOfStream(Row nextElement) {
        return false;
    }

    @Override
    public TypeInformation<Row> getProducedType() {
        return typeInfo;
    }

    /**
     * Configures the failure behaviour if a JSON field is missing.
     *
     * <p>By default, a missing field is ignored and the field is set to null.
     *
     * @param failOnMissingField Flag indicating whether to fail or not on a missing field.
     */
    public void setFailOnMissingField(boolean failOnMissingField) {
        this.failOnMissingField = failOnMissingField;
    }
}

FlinkKafkaDemo.scala

package com.woople.streaming.scala.examples.kafka
import java.util.Properties
import com.woople.flink.streaming.connectors.kafka.{CsvRowDeserializationSchema, KafkaCsvTableSource}
import org.apache.flink.api.common.typeinfo.{TypeInformation, Types}
import org.apache.flink.api.java.typeutils.RowTypeInfo
import org.apache.flink.api.scala._
import org.apache.flink.streaming.api.scala.{DataStream, StreamExecutionEnvironment}
import org.apache.flink.streaming.connectors.kafka.Kafka09JsonTableSink
import org.apache.flink.streaming.connectors.kafka.partitioner.FlinkFixedPartitioner
import org.apache.flink.table.api.TableEnvironment
import org.apache.flink.table.api.scala._
import org.apache.flink.types.Row

object FlinkKafkaDemo {

  def main(args: Array[String]) {
    val env = StreamExecutionEnvironment.getExecutionEnvironment
    val tableEnv = TableEnvironment.getTableEnvironment(env)
    val typeInfo = Types.ROW_NAMED(Array("imsi","lac","cell"), Types.STRING, Types.STRING, Types.STRING)

    val properties = new Properties()
    properties.setProperty("bootstrap.servers", "10.1.236.66:6667")
    properties.setProperty("group.id", "test")

    //Register a TableSource
    val kafkaTableSource = new KafkaCsvTableSource(
      "foo",
      properties,
      new CsvRowDeserializationSchema(typeInfo),
      typeInfo)

    tableEnv.registerTableSource("KafkaCsvTable", kafkaTableSource)
    val kafkaCsvTable = tableEnv.scan("KafkaCsvTable")
    val filterResult = kafkaCsvTable.where('imsi like "460%").select("imsi,lac,cell")
    val dsRow: DataStream[Row] = tableEnv.toAppendStream(filterResult)

    {
      val types = Array[TypeInformation[_]](
        Types.STRING,
        Types.STRING,
        Types.STRING,
        Types.BOOLEAN,
        Types.LONG)
      val names =  Array("imsi","lac","cell","isSpecifiedLocation","timestamp")

      implicit val tpe: TypeInformation[Row] = new RowTypeInfo(types, names)

      val newDsRows = dsRow.map(row => {
        val ret = new Row(row.getArity() + 2)

        for(i <- 0 to row.getArity()-1) {
          ret.setField(i, row.getField(i))
        }

        val isSpecifiedLocation = if(ret.getField(1).equals(ret.getField(2))) true else false
        ret.setField(row.getArity(), isSpecifiedLocation)

        ret.setField(row.getArity()+1, System.currentTimeMillis())

        ret
      })

      tableEnv.registerDataStream("newTable", newDsRows)
      val newKafkaCsvTable = tableEnv.scan("newTable")
      val newResult = newKafkaCsvTable.filter('isSpecifiedLocation === true).select("imsi,lac,cell,isSpecifiedLocation,timestamp")

      val sink = new Kafka09JsonTableSink("bar", properties, new FlinkFixedPartitioner[Row])
      newResult.writeToSink(sink)
      env.execute("Flink kafka demo")
    }
  }
}

总结

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本文只是一个简单的样例，代码中并没有考虑性能等因素。后续会对相关内容进行深入的研究。