Google DataFlow Apache Beam

Question

我试图使用Apache Beam创建一个Dataflow管道,我无法按照文档,找不到任何示例.

管道很简单.

1. 创建一个管道
2. 阅读pub/sub主题
3. 写入扳手.

目前,我陷入了第2步.我找不到任何关于如何从pub/sub读取并使用它的示例.

这是我到目前为止所希望的代码

class ExtractFlowInfoFn extends DoFn<PubsubMessage, KV<String, String>> {
    public void processElement(ProcessContext c) {
        KV.of("key", "value");
    }
}

public static void main(String[] args) {

    Pipeline p = Pipeline.create(
    PipelineOptionsFactory.fromArgs(args).withValidation().create());

    p.apply("ReadFromPubSub", PubsubIO.readMessages().fromSubscription("test"))
     .apply("ConvertToKeyValuePair", ParDo.of(new ExtractFlowInfoFn()))
     .apply("WriteToLog", ));
};

我通过以下几个例子来提出代码.说实话,我不知道我在这做什么.

请帮助我理解这一点或将我链接到正确的文档.

Answer 1

从Pub/Sub中提取消息并写入Cloud Spanner的示例:

import com.google.cloud.spanner.Mutation;
import org.apache.beam.sdk.io.gcp.spanner.SpannerIO;
import org.apache.beam.sdk.transforms.DoFn.ProcessElement;

class MessageToMutationDoFn extends DoFn<PubsubMessage, Mutation> {

    @ProcessElement
    public void processElement(ProcessContext c) {

        // TODO: create Mutation object from PubsubMessage

        Mutation mutation = Mutation.newInsertBuilder("users_backup2")
            .set("column_1").to("value_1")
            .set("column_2").to("value_2")
            .set("column_3").to("value_3")
            .build();

        c.output(mutation);
    }
}

public static void main(String[] args) {

    Pipeline p = Pipeline.create();

    p.apply("ReadFromPubSub", PubsubIO.readMessages().fromSubscription("test"))
     .apply("MessageToMutation", ParDo.of(new MessageToMutationDoFn()))
     .apply("WriteToSpanner", SpannerIO.write()
         .withProjectId("projectId")
         .withInstanceId("spannerInstanceId")
         .withDatabaseId("spannerDatabaseId"));

    p.run();
}

参考:Apache Beam SpannerIO,Apache Beam PubsubIO