Custom Source Stream

Compile code to obtain data from the desired cloud ecosystem or open-source ecosystem as the input data of Flink jobs.

Syntax

    
         CREATE SOURCE STREAM stream_id (attr_name attr_type (',' attr_name attr_type)* )
  WITH (
    type = "user_defined",
    type_class_name = "",
    type_class_parameter = ""
  )
  (TIMESTAMP BY timeindicator (',' timeindicator)?);timeindicator:PROCTIME '.' PROCTIME| ID '.' ROWTIME

Keyword

**Table 1** Keyword description
Parameter	Mandatory	Description
type	Yes	Data source type. The value user_defined indicates that the data source is a user-defined data source.
type_class_name	Yes	Name of the source class for obtaining source data. The value must contain the complete package path.
type_class_parameter	Yes	Input parameter of the user-defined source class. Only one parameter of the string type is supported.

Precautions

The user-defined source class needs to inherit the RichParallelSourceFunction class and specify the data type as Row. For example, define MySource class: public class MySource extends RichParallelSourceFunction<Row>{}. It aims to implement the open, run, and close functions.

Dependency pom:

<dependency>
	<groupId>org.apache.flink</groupId>
	<artifactId>flink-streaming-java_2.11</artifactId>
	<version>${flink.version}</version>
	<scope>provided</scope>
</dependency>
<dependency>
	<groupId>org.apache.flink</groupId>
	<artifactId>flink-core</artifactId>
	<version>${flink.version}</version>
	<scope>provided</scope>
</dependency>

Example

A data record is generated in each period. The data record contains only one field of the INT type. The initial value is 1 and the period is 60 seconds. The period is specified by an input parameter.

   
        CREATE SOURCE STREAM user_in_data (
	count INT
     )
  WITH (  
	type = "user_defined", 
	type_class_name = "mySourceSink.MySource", 
	type_class_parameter = "60"
      )
      TIMESTAMP BY car_timestamp.rowtime;