Flink 流转表，表转流，watermark设置

qzWsong2024-08-20 9:40

首先创建一个流

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@Data
@AllArgsConstructor
@NoArgsConstructor
public static class Nan {
    private String xing;
    private String name;
    private Long ts;
}


StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
env.setParallelism(1);
StreamTableEnvironment tenv = StreamTableEnvironment.create(env);

DataStreamSource<String> sourceNan = env.socketTextStream("hdp01", 1111);
DataStreamSource<String> sourceNv = env.socketTextStream("hdp01", 2222);

System.setProperty("java.net.preferIPv4Stack", "true");

SingleOutputStreamOperator<Nan> beanNan = sourceNan.map(new MapFunction<String, Nan>() {
    @Override
    public Nan map(String s) throws Exception {
        try {
            String[] split = s.split(",");
            return new Nan(split[0].substring(0, 1), split[1], Long.parseLong(split[2]));
        } catch (Exception e) {
            return null;
        }
    }
}).filter(Objects::nonNull).assignTimestampsAndWatermarks(
        WatermarkStrategy.<Nan>forMonotonousTimestamps().withTimestampAssigner(new SerializableTimestampAssigner<Nan>() {
    @Override
    public long extractTimestamp(Nan nan, long l) {
        return nan.getTs();
    }
})).returns(TypeInformation.of(Nan.class));

流转表

流转表的时候有一个点要注意，watermark必须要重新指定，否则会丢失，常用的方式如下

1、沿用流上的watermark

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tenv.createTemporaryView("nan", beanNan, Schema.newBuilder()
        .column("xing", DataTypes.STRING())
        .column("name", DataTypes.STRING())
        .column("ts", DataTypes.TIMESTAMP_LTZ(3))
        .watermark("rt","source_watermark()")
        .build() );

2、重新创建watermark

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tenv.createTemporaryView("nan", beanNan, Schema.newBuilder()
        .column("xing", DataTypes.STRING())
        .column("name", DataTypes.STRING())
        .column("rt", DataTypes.BIGINT())
        .watermark("rt","rt - interval '1' second")
        .build() );

3、根据内置属性rowtime创建watermark

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tenv.createTemporaryView("nan1", beanNan, Schema.newBuilder()
        .column("xing", DataTypes.STRING())
        .column("name", DataTypes.STRING())
        .column("ts", DataTypes.BIGINT())
        .columnByMetadata("rt", DataTypes.TIMESTAMP_LTZ(3),"rowtime")
        .watermark("rt","rt - interval '1' second")
        .build() );

使用表

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TableResult tableResult = tenv.executeSql("select *,current_watermark(rt) from nan");
tableResult.print();