是否可以创建从Pub / Sub读取数据并写入数据存储区的管道？在我的代码中，我将PubsubIO指定为输入，并应用窗口来获取有界PCollection，但似乎无法使用带有options.setStreaming的DatastoreIO.writeTo为true，而这是必需的以便使用PubsubIO作为输入。有没有解决的办法？或者是不可能从pubsub读取并写入数据存储区？
这是我的代码：
DataflowPipelineOptions options = PipelineOptionsFactory.create()
.as(DataflowPipelineOptions.class);
options.setRunner(DataflowPipelineRunner.class);
options.setProject(projectName);
options.setStagingLocation("gs://my-staging-bucket/staging");
options.setStreaming(true);
Pipeline p = Pipeline.create(options);
PCollection<String> input = p.apply(PubsubIO.Read.topic("projects/"+projectName+"/topics/event-streaming"));
PCollection<String> inputWindow = input.apply(Window.<String>into(FixedWindows.of(Duration.standardSeconds(5))).triggering(AfterPane.elementCountAtLeast(1)).discardingFiredPanes().withAllowedLateness(Duration.standardHours(1)));
PCollection<String> inputDecode = inputWindow.apply(ParDo.of(new DoFn<String, String>() {
private static final long serialVersionUID = 1L;
public void processElement(ProcessContext c) {
String msg = c.element();
byte[] decoded = Base64.decodeBase64(msg.getBytes());
String outmsg = new String(decoded);
c.output(outmsg);
}
}));
PCollection<DatastoreV1.Entity> inputEntity = inputDecode.apply(ParDo.of(new CreateEntityFn("stream", "events")));
inputEntity.apply(DatastoreIO.writeTo(datasetid));
p.run();
这是我得到的例外：
Exception in thread "main" java.lang.UnsupportedOperationException: The Write transform is not supported by the Dataflow streaming runner.
at com.google.cloud.dataflow.sdk.runners.DataflowPipelineRunner$StreamingWrite.apply(DataflowPipelineRunner.java:488)
at com.google.cloud.dataflow.sdk.runners.DataflowPipelineRunner$StreamingWrite.apply(DataflowPipelineRunner.java:480)
at com.google.cloud.dataflow.sdk.runners.PipelineRunner.apply(PipelineRunner.java:74)
at com.google.cloud.dataflow.sdk.runners.DataflowPipelineRunner.apply(DataflowPipelineRunner.java:314)
at com.google.cloud.dataflow.sdk.Pipeline.applyInternal(Pipeline.java:358)
at com.google.cloud.dataflow.sdk.Pipeline.applyTransform(Pipeline.java:267)
at com.google.cloud.dataflow.sdk.runners.DataflowPipelineRunner.apply(DataflowPipelineRunner.java:312)
at com.google.cloud.dataflow.sdk.Pipeline.applyInternal(Pipeline.java:358)
at com.google.cloud.dataflow.sdk.Pipeline.applyTransform(Pipeline.java:267)
at com.google.cloud.dataflow.sdk.values.PCollection.apply(PCollection.java:159)
at my.own.project.google.dataflow.EventStreamingDataflow.main(EventStreamingDataflow.java:104)
答案 0 :(得分：5)
流媒体运行时当前不支持DatastoreIO接收器。要从流管道写入数据存储区，您可以从DoFn直接调用数据存储区API。
答案 1 :(得分：5)
好吧，经过大量撞击墙壁后，我终于开始工作了。像danielm建议的那样，我从ParDo DoFn调用Datastore API。一个问题是，我没有意识到有一个单独的API可以在AppEngine之外使用Cloud Datastore。 （com.google.api.services.datastore ...与com.google.appengine.api.datastore ...）。另一个问题是，最新版本的Cloud Datastore API显然存在某种错误（google-api-services-datastore-protobuf v1beta2-rev1-4.0.0，我收到了IllegalAccessError），我通过使用旧版本（v1beta2-rev1-2.1.2）。
所以，这是我的工作代码：
import com.google.cloud.dataflow.sdk.Pipeline;
import com.google.cloud.dataflow.sdk.io.PubsubIO;
import com.google.cloud.dataflow.sdk.options.DataflowPipelineOptions;
import com.google.cloud.dataflow.sdk.options.PipelineOptionsFactory;
import com.google.cloud.dataflow.sdk.runners.DataflowPipelineRunner;
import com.google.cloud.dataflow.sdk.transforms.DoFn;
import com.google.cloud.dataflow.sdk.transforms.ParDo;
import com.google.cloud.dataflow.sdk.values.PCollection;
import com.google.api.services.datastore.DatastoreV1.*;
import com.google.api.services.datastore.client.Datastore;
import com.google.api.services.datastore.client.DatastoreException;
import com.google.api.services.datastore.client.DatastoreFactory;
import static com.google.api.services.datastore.client.DatastoreHelper.*;
import java.security.GeneralSecurityException;
import java.io.IOException;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import org.json.simple.parser.ParseException;
//--------------------
public static void main(String[] args) {
DataflowPipelineOptions options = PipelineOptionsFactory.create()
.as(DataflowPipelineOptions.class);
options.setRunner(DataflowPipelineRunner.class);
options.setProject(projectName);
options.setStagingLocation("gs://my-staging-bucket/staging");
options.setStreaming(true);
Pipeline p = Pipeline.create(options);
PCollection<String> input = p.apply(PubsubIO.Read.topic("projects/"+projectName+"/topics/my-topic-name"));
input.apply(ParDo.of(new DoFn<String, String>() {
private static final long serialVersionUID = 1L;
public void processElement(ProcessContext c) throws ParseException, DatastoreException {
JSONObject json = (JSONObject)new JSONParser().parse(c.element());
Datastore datastore = null;
try {
datastore = DatastoreFactory.get().create(getOptionsFromEnv()
.dataset(datasetid).build());
} catch (GeneralSecurityException exception) {
System.err.println("Security error connecting to the datastore: " + exception.getMessage());
} catch (IOException exception) {
System.err.println("I/O error connecting to the datastore: " + exception.getMessage());
}
Key.Builder keyBuilder = makeKey("my-kind");
keyBuilder.getPartitionIdBuilder().setNamespace("my-namespace");
Entity.Builder event = Entity.newBuilder()
.setKey(keyBuilder);
event.addProperty(makeProperty("my-prop",makeValue((String)json.get("my-prop"))));
CommitRequest commitRequest = CommitRequest.newBuilder()
.setMode(CommitRequest.Mode.NON_TRANSACTIONAL)
.setMutation(Mutation.newBuilder().addInsertAutoId(event))
.build();
if(datastore!=null){
datastore.commit(commitRequest);
}
}
}));
p.run();
}
pom.xml中的依赖项：
<dependency>
<groupId>com.google.cloud.dataflow</groupId>
<artifactId>google-cloud-dataflow-java-sdk-all</artifactId>
<version>[1.0.0,2.0.0)</version>
</dependency>
<dependency>
<groupId>com.google.apis</groupId>
<artifactId>google-api-services-datastore-protobuf</artifactId>
<version>v1beta2-rev1-2.1.2</version>
</dependency>
<dependency>
<groupId>com.google.http-client</groupId>
<artifactId>google-http-client</artifactId>
<version>1.17.0-rc</version>
</dependency>
<!-- Some more.. like JUnit etc.. -->