版本：1.x

Plugin development

Introduction to plugin system

The seatunnel plugin is divided into three parts, Input, Filter and Output

Input

Input is responsible for converting the data of the external data source into DStream[(String, String)]

Filter

Filter is a transform operation, responsible for operating on the data structure of Dataset[Row]

Output

Output is the action operation, which is responsible for outputting the Dataset[Row] to an external data source or printing it to terminal

Ready to work

seatunnel supports Java/Scala as a development language for plug-ins, among which Scala is recommended for the Input plug-in, and both Java and Scala are available for other types of plug-ins.

Create a new Java/Scala project, or you can directly pull seatunnel-filter-example, and then make modifications on this project

1. Create a new pom.xml

Reference file pom.xml

Add the interface provided by seatunnel to the project's dependencies

<dependency>
    <groupId>io.github.interestinglab.seatunnel</groupId>
    <artifactId>seatunnel-apis_2.11</artifactId>
    <version>1.1.0</version>
</dependency>

2. Implement your own method

Input (live stream)

Create a new class and inherit the parent class BaseInput provided by seatunnel-apis

class ScalaHdfs extends BaseStreamingInput {

  var config: Config = ConfigFactory.empty()

  /**
    * SetConfig.
    **/
  override def setConfig(config: Config): Unit = {
    this.config = config
  }

  /**
    * GetConfig.
    **/
  override def getConfig(): Config = {
    this.config
  }

Override the checkConfig, prepare and getDstream methods defined by the parent class

override def checkConfig(): (Boolean, String) = {}
override def prepare(spark: SparkSession): Unit = {}
override def getDStream(ssc: StreamingContext): DStream[(String, String)] = {}

When the Input plugin is called, it will first execute the checkConfig method to check whether the parameters passed in when calling the plugin are correct, then call the prepare method to configure the default values of the parameters and initialize the member variables of the class, and finally call the getStream method converts external data source to DStream[(String, String)]
Scala version Input plugin implementation refer to [ScalaHdfs](https://github.com/InterestingLab/seatunnel-filter-example/blob/master/src/main/scala/org/interestinglab/seatunnel/input/ScalaHdfs .scala)

Filter

Create a new class and inherit the parent class BaseFilter provided by seatunnel-apis

class ScalaSubstring extends BaseFilter {

  var config: Config = ConfigFactory.empty()

  /**
    * SetConfig.
    **/
  override def setConfig(config: Config): Unit = {
    this.config = config
  }

  /**
    * GetConfig.
    **/
  override def getConfig(): Config = {
    this.config
  }
}

public class JavaSubstring extends BaseFilter {

    private Config config;

    @Override
    public Config getConfig() {
        return config;
    }

    @Override
    public void setConfig(Config config) {
        this.config = config;
    }
}

Override the checkConfig, prepare and process methods defined by the parent class
```
override def checkConfig(): (Boolean, String) = {}
override def prepare(spark: SparkSession): Unit = {}
override def process(spark: SparkSession, ds: Dataset[Row]): Dataset[Row] = {}
```
```
@Override
public Tuple2<Object, String> checkConfig() {}
@Override
public void prepare(SparkSession spark, StreamingContext ssc) {}
@Override
public Dataset<Row> process(SparkSession spark, Dataset<Row> df) {}
```
- When the Filter plugin is called, it will first execute the checkConfig method to check whether the parameters passed in when calling the plugin are correct, then call the prepare method to configure the default values of the parameters and initialize the member variables of the class, and finally call the The process method processes data in Dataset[Row] format.
- For the implementation of the Filter plugin in the Java version, refer to [JavaSubstring](https://github.com/InterestingLab/seatunnel-filter-example/blob/master/src/main/java/org/interestinglab/seatunnel/filter/ JavaSubstring.java), the implementation of the Scala version Filter plugin refers to [ScalaSubstring](https://github.com/InterestingLab/seatunnel-filter-example/blob/master/src/main/scala/org/interestinglab/ seatunnel/filter/ScalaSubstring.scala)

Output

Create a new class and inherit the parent class BaseOutput provided by seatunnel-apis

class ScalaStdout extends BaseOutput {


  var config: Config = ConfigFactory.empty()

  /**
    * SetConfig.
    **/
  override def setConfig(config: Config): Unit = {
    this.config = config
  }

  /**
    * GetConfig.
    **/
  override def getConfig(): Config = {
    this.config
  }
}

public class JavaStdout extends BaseOutput {

    private Config config;

    @Override
    public Config getConfig() {
        return config;
    }

    @Override
    public void setConfig(Config config) {
        this.config = config;
    }
}

Override the checkConfig, prepare and process methods defined by the parent class

override def checkConfig(): (Boolean, String) = {}
override def prepare(spark: SparkSession): Unit = {}
override def process(spark: SparkSession, ds: Dataset[Row]): Dataset[Row] = {}

@Override
public Tuple2<Object, String> checkConfig() {}
@Override
public void prepare(SparkSession spark) {}
@Override
public Dataset<Row> process(SparkSsession spark, Dataset<Row> ds) {}

Output plugin call structure is similar to Filter plugin. When calling, it will first execute the checkConfig method to check whether the parameters passed in when calling the plugin are correct, then call the prepare method to configure the default values of the parameters and initialize the member variables of the class, and finally call the process method to set the Dataset [Row] format data output to an external data source.
For the implementation of the Output plugin in the Java version, refer to [JavaStdout](https://github.com/InterestingLab/seatunnel-filter-example/blob/master/src/main/java/org/interestinglab/seatunnel/output/ JavaStdout.java), the implementation of the Scala version Output plugin refers to [ScalaStdout](https://github.com/InterestingLab/seatunnel-filter-example/blob/master/src/main/scala/org/interestinglab/ seatunnel/output/ScalaStdout.scala)

UDFs

Create a new class and inherit the parent class BaseFilter provided by seatunnel-apis

class ScalaSubstring extends BaseFilter {

  var config: Config = ConfigFactory.empty()

  /**
    * SetConfig.
    **/
  override def setConfig(config: Config): Unit = {
    this.config = config
  }

  /**
    * GetConfig.
    **/
  override def getConfig(): Config = {
    this.config
  }
}

Override the checkConfig, prepare, getUdfList and process methods defined by the parent class. Only the getUdfList and process methods are introduced here

override def getUdfList(): List[(String, UserDefinedFunction)] = {
  val func = udf((s: String, pos: Int, len: Int) => s. substring(pos, pos+len))
  List(("my_sub", func))
}
override def process(spark: SparkSession, ds: Dataset[Row]): Dataset[Row] = {
  val srcField = config.getString("source_field")
  val targetField = config.getString("target_field")
  val pos = config.getInt("pos")
  val len = config.getInt("len")
  val func = getUdfList().get(0)._2
  df.withColumn(targetField, func(col(srcField), lit(pos), lit(len)))
}

For a complete case of UDF plug-in development, refer to [ScalaSubstring](https://github.com/InterestingLab/seatunnel-example/blob/rickyhuo.fea.udf/src/main/scala/org/interestinglab/seatunnel/filter/ScalaSubstring.scala #L15)

New META-INF/services
Seatunnel will use the Service loader mechanism to register the method that implements io.github.interestinglab.seatunnel.apis.BaseFilter as UDF according to the method returned by getUdfList. If the interface implementation class is not specified in services, it will not be used. will be registered as a UDF.
[META-INF] in the case (https://github.com/InterestingLab/seatunnel-example/blob/master/src/main/resources/META-INF/services/io.github.interestinglab.seatunnel.apis.BaseFilter )

3. Package and use

Packaging
mvn package
Put the packaged Jar package in the seatunnel plugins directory
```
cd seatunnel-1.1.0
mkdir -p plugins/my_plugins/lib
cd plugins/my_plugins/lib
```
Seatunnel needs to put the third-party Jar package, and must create a new lib folder
plugins/your_plugin_name/lib/your_jar_name
other files in
plugins/your_plugin_name/files/your_file_name

Use plugins in configuration files

Here is a complete example using a third-party plugin and putting it in config/application.conf

The test data is generated by the Fake plugin, split with Split, then the third-party plugin ScalaSubstring is used to intercept the string, and finally the third-party plugin JavaStdout is used to print to the terminal.

spark {
    spark.streaming.batchDuration = 5
    spark.app.name = "seatunnel-sample"
    spark.ui.port = 13000
    spark.executor.instances = 2
    spark.executor.cores = 1
    spark.executor.memory = "1g"
}

input {
    fakeStream {
        content = ["INFO : gary is 28 years old", "WARN : suwey is 16 years old"]
        rate = 5
    }
}

filter {
    split {
        fields = ["log_level", "message"]
        delimiter = ":"
    }
    sql = {
        table_name = "tmp"
        # use UDF
        sql = "select log_level, my_sub(message, 1, 3) from tmp"
    }
}

output {
    org.interestinglab.seatunnel.output.JavaStdout {
        limit = 2
    }
}

Start seatunnel

./bin/start-seatunnel.sh --config config/application.conf --deploy-mode client --master local[2]

View the results

+---------+--------------------------------+
|log_level|UDF(message, 1, 3)|
+---------+--------------------------------+
|INFO |ary |
|INFO |ary |
+---------+--------------------------------+
only showing top 2 rows

Plugin development

Introduction to plugin system​

Input​

Filter​

Output​

Ready to work​

1. Create a new pom.xml​

2. Implement your own method​

Input (live stream)​

Filter​

Output​

UDFs​

3. Package and use​

Introduction to plugin system

Input

Filter

Output

Ready to work

1. Create a new pom.xml

2. Implement your own method

Input (live stream)

Filter

Output

UDFs

3. Package and use