Pub / Sub本地模拟器

发布/订阅是GCP提供的不错的工具。它非常方便，可以帮助您解决应用程序可能面临的消息传递难题。实际上，如果您使用GCP，则可以使用托管消息解决方案。

如预期的那样，使用实际的发布/订阅解决方案需要一定的配额，因此对于

开发中，必须使用不会花钱的东西。

在这些情况下，您可以使用Pub / Sub 仿真器。要开始使用模拟器，您需要先安装它

 gcloud components install pubsub-emulator

确实很方便，但是具有docker映像，因为它更便于携带。不幸的是，没有来自Google Cloud的官方图片，但是您可以使用Docker Hub上可用的解决方案之一。

现在运行它

 gcloud beta emulators pubsub start --project= test -project

之后，您的应用程序可以连接到发布/订阅模拟器。默认端口为8085

我将以Java单元测试为例。

 package org.gkatzioura.pubsub;  import java.io.IOException;  import java.nio.charset.Charset;  import org.junit.After;  import org.junit.Assert;  import org.junit.Before;  import org.junit.Test;  import com.google.api.gax.core.CredentialsProvider;  import com.google.api.gax.core.NoCredentialsProvider;  import com.google.api.gax.grpc.GrpcTransportChannel;  import com.google.api.gax.rpc.FixedTransportChannelProvider;  import com.google.api.gax.rpc.TransportChannelProvider;  import com.google.cloud.pubsub.v1.Publisher;  import com.google.cloud.pubsub.v1.SubscriptionAdminClient;  import com.google.cloud.pubsub.v1.SubscriptionAdminSettings;  import com.google.cloud.pubsub.v1.TopicAdminClient;  import com.google.cloud.pubsub.v1.TopicAdminSettings;  import com.google.cloud.pubsub.v1.stub.GrpcSubscriberStub;  import com.google.cloud.pubsub.v1.stub.SubscriberStub;  import com.google.cloud.pubsub.v1.stub.SubscriberStubSettings;  import com.google.protobuf.ByteString;  import com.google.pubsub.v1.ProjectSubscriptionName;  import com.google.pubsub.v1.ProjectTopicName;  import com.google.pubsub.v1.PubsubMessage;  import com.google.pubsub.v1.PullRequest;  import com.google.pubsub.v1.PullResponse;  import com.google.pubsub.v1.PushConfig;  import com.google.pubsub.v1.Subscription;  import io.grpc.ManagedChannel;  import io.grpc.ManagedChannelBuilder;  public class LocalPubSubTest { private static final String PROJECT = "test-project" ; private static final String SUBSCRIPTION_NAME = "SUBSCRIBER" ; private static final String TOPIC_NAME = "test-topic-id" ; private static final String hostPort = "127.0.0.1:8085" ; private ManagedChannel channel; private TransportChannelProvider channelProvider; private TopicAdminClient topicAdmin; private Publisher publisher; private SubscriberStub subscriberStub; private SubscriptionAdminClient subscriptionAdminClient; private ProjectTopicName topicName = ProjectTopicName.of(PROJECT, TOPIC_NAME); private ProjectSubscriptionName subscriptionName = ProjectSubscriptionName.of(PROJECT, SUBSCRIPTION_NAME); private Subscription subscription; @Before public void setUp() throws Exception { channel = ManagedChannelBuilder.forTarget(hostPort).usePlaintext().build(); channelProvider = FixedTransportChannelProvider.create(GrpcTransportChannel.create(channel)); CredentialsProvider credentialsProvider = NoCredentialsProvider.create(); topicAdmin = createTopicAdmin(credentialsProvider); topicAdmin.createTopic(topicName); publisher = createPublisher(credentialsProvider); subscriberStub = createSubscriberStub(credentialsProvider); subscriptionAdminClient = createSubscriptionAdmin(credentialsProvider); subscription = subscriptionAdminClient.createSubscription(subscriptionName, topicName, PushConfig.getDefaultInstance(), 0); } @After public void tearDown() throws Exception { topicAdmin.deleteTopic(topicName); subscriptionAdminClient.deleteSubscription(subscription.getName()); channel.shutdownNow(); } @Test public void testLocalPubSub() throws Exception { final String messageText = "text" ; PubsubMessage pubsubMessage = PubsubMessage.newBuilder() .setData(ByteString.copyFrom(messageText, Charset.defaultCharset())) .build(); publisher.publish(pubsubMessage).get(); PullRequest pullRequest = PullRequest.newBuilder() .setMaxMessages(1) .setReturnImmediately( true ) // if messages are not available immediately return .setSubscription(subscription.getName()) .build(); PullResponse pullResponse = subscriberStub.pullCallable().call(pullRequest); String receiveMessageText = pullResponse.getReceivedMessages(0).getMessage().getData().toStringUtf8(); Assert.assertEquals(messageText, receiveMessageText); } private TopicAdminClient createTopicAdmin(CredentialsProvider credentialsProvider) throws IOException { return TopicAdminClient.create( TopicAdminSettings.newBuilder() .setTransportChannelProvider(channelProvider) .setCredentialsProvider(credentialsProvider) .build() ); } private SubscriptionAdminClient createSubscriptionAdmin(CredentialsProvider credentialsProvider) throws IOException { SubscriptionAdminSettings subscriptionAdminSettings = SubscriptionAdminSettings.newBuilder() .setCredentialsProvider(credentialsProvider) .setTransportChannelProvider(channelProvider) .build(); return SubscriptionAdminClient.create(subscriptionAdminSettings); } private Publisher createPublisher(CredentialsProvider credentialsProvider) throws IOException { return Publisher.newBuilder(topicName) .setChannelProvider(channelProvider) .setCredentialsProvider(credentialsProvider) .build(); } private SubscriberStub createSubscriberStub(CredentialsProvider credentialsProvider) throws IOException { SubscriberStubSettings subscriberStubSettings = SubscriberStubSettings.newBuilder() .setTransportChannelProvider(channelProvider) .setCredentialsProvider(credentialsProvider) .build(); return GrpcSubscriberStub.create(subscriberStubSettings); }  }

而已。现在您可以进行一些具有成本效益的单元测试！