java本地Pubsub仿真器无法与数据流一起工作

Question

我正在用Java开发数据流，输入来自Pubsub。后来，我看到了一个关于如何使用本地Pubsub仿真器的指南here，这样我就不需要为了测试而部署到GCP

以下是我的简单代码：

private interface Options extends PipelineOptions, PubsubOptions, StreamingOptions {

    @Description("Pub/Sub topic to read messages from")
    String getTopic();
    void setTopic(String topic);

    @Description("Pub/Sub subscription to read messages from")
    String getSubscription();
    void setSubscription(String subscription);

    @Description("Local file output")
    String getOutput();
    void setOutput(String output);
}

public static void main(String[] args) {

    Options options = PipelineOptionsFactory
            .fromArgs(args)
            .withValidation()
            .as(Options.class);
    options.setStreaming(true);
    options.setPubsubRootUrl("localhost:8085");

    Pipeline pipeline = Pipeline.create(options);
    pipeline
        .apply("IngestFromPubsub", PubsubIO.readStrings().fromTopic(options.getTopic()))
        // other .apply's

    pipeline.run();

}

我能够遵循指南，包括我需要使用示例Python代码创建主题、订阅、发布者甚至发布消息的部分。当我使用Python代码与Pubsub仿真器交互时，我注意到运行仿真器的命令行中的消息Detected HTTP/2 connection：

Executing: cmd /c C:\...\google-cloud-sdk\platform\pubsub-emulator\bin\cloud-pubsub-emulator.bat --host=localhost --port=8085
[pubsub] This is the Google Pub/Sub fake.
[pubsub] Implementation may be incomplete or differ from the real system.
[pubsub] Apr 10, 2020 3:33:26 PM com.google.cloud.pubsub.testing.v1.Main main
[pubsub] INFO: IAM integration is disabled. IAM policy methods and ACL checks are not supported
[pubsub] Apr 10, 2020 3:33:26 PM io.gapi.emulators.netty.NettyUtil applyJava7LongHostnameWorkaround
[pubsub] INFO: Unable to apply Java 7 long hostname workaround.
[pubsub] Apr 10, 2020 3:33:27 PM com.google.cloud.pubsub.testing.v1.Main main
[pubsub] INFO: Server started, listening on 8085
[pubsub] Apr 10, 2020 3:34:38 PM io.gapi.emulators.grpc.GrpcServer$3 operationComplete
[pubsub] INFO: Adding handler(s) to newly registered Channel.
[pubsub] Apr 10, 2020 3:34:38 PM io.gapi.emulators.netty.HttpVersionRoutingHandler channelRead
[pubsub] INFO: Detected HTTP/2 connection.
[pubsub] Apr 10, 2020 3:34:52 PM io.gapi.emulators.grpc.GrpcServer$3 operationComplete
[pubsub] INFO: Adding handler(s) to newly registered Channel.
[pubsub] Apr 10, 2020 3:34:52 PM io.gapi.emulators.netty.HttpVersionRoutingHandler channelRead
[pubsub] INFO: Detected HTTP/2 connection.

我使用Dataflow Pipeline run配置在Eclipse中编译/运行代码，但遇到了一个问题

Exception in thread "main" org.apache.beam.sdk.Pipeline$PipelineExecutionException: java.lang.RuntimeException: Failed to create subscription: 
...
Caused by: java.lang.RuntimeException: Failed to create subscription: 
    at org.apache.beam.sdk.io.gcp.pubsub.PubsubUnboundedSource.createRandomSubscription(PubsubUnboundedSource.java:1427)
...
Caused by: java.lang.IllegalArgumentException: java.net.MalformedURLException: unknown protocol: localhost
...
Caused by: java.net.MalformedURLException: unknown protocol: localhost

当我尝试在options.setPubsubRootUrl("localhost:8085")行中添加http时，我得到一个无限重复的异常：

com.google.api.client.http.HttpRequest execute
WARNING: exception thrown while executing request
java.net.ConnectException: Connection refused: connect
    at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method)
    at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
    at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
    at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
    at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
    at java.net.PlainSocketImpl.connect(Unknown Source)
    at java.net.SocksSocketImpl.connect(Unknown Source)

它似乎到达了Pubsub仿真器，但无法连接，因为我运行仿真器的命令行会无限地生成以下内容：

[pubsub] Apr 10, 2020 3:49:30 PM io.gapi.emulators.grpc.GrpcServer$3 operationComplete
[pubsub] INFO: Adding handler(s) to newly registered Channel.
[pubsub] Apr 10, 2020 3:49:30 PM io.gapi.emulators.netty.HttpVersionRoutingHandler channelRead
[pubsub] INFO: Detected non-HTTP/2 connection.

如何使用Pubsub模拟器使数据流工作

Answer 1

您正试图使用Beam 2.5 SDK的数据流分支，从Beam Direct Runner连接到Pubsub仿真器。截至2019年6月6日，Dataflow 2.5 SDK和Eclipse插件已被弃用。然而，这应该是可行的

正如您所发现的，您需要在Beam中为PubSubroToUrl加上“http://”前缀。您看到的第二个问题表明localhost:8085上没有任何内容在监听。这可能是因为实际上有两个本地主机：IPv4和IPv6。Pubsub Emulator只监听IPv4，Windows会先尝试IPv6。尝试用127.0.0.1替换localhost以强制IPv4。你应该以这样的方式结束：

options.setPubsubRootUrl("http://127.0.0.1:8085")