Grpc系列一第一個hello world 例子

WindySky 2017-08-01

展開全文

1. 概念

gRPC的定義：

一個高性能、通用的開源RPC框架
主要面向移動應用開發： gRPC提供了一種簡單的方法來精確地定義服務和為iOS、Android和后臺支持服務自動生成可靠性很強的客戶端功能庫。
基于HTTP/2協議標準而設計，基于ProtoBuf(Protocol Buffers)序列化協議開發
支持眾多開發語言

2. Hello world Demo

主要流程：
1. 通過.proto文件定義服務
2. 通過protocol buffer compiler插件生成客戶端和服務端
3. 通過grpc API生成客戶端和服務端代碼

2.1 定義RPC服務 proto

// 如果使用此注釋，則使用proto3; 否則使用proto2
syntax = "proto3";
// 生成類的包名
option java_package = "com.hry.spring.grpc.simple";
//生成的數據訪問類的類名，如果沒有指定此值，則生成的類名為proto文件名的駝峰命名方法
option java_outer_classname = "GreeterEntity";
option java_multiple_files = true;

service Greeter {
  rpc SayHello (HelloRequest) returns (HelloReply) {}
}

message HelloRequest {
  string name = 1;
}

message HelloReply {
  string message = 1;
}
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2.2 生成基礎類

通過proto里的方法生成基礎類
通過Protobuf3 的第一個Java demo的步驟生成protobuf3相關代碼，如HelloReply,HelloReplyOrBuilder,HelloRequest,HelloRequestOrBuilder，詳細見github代碼
生成GreeterGrpc

a. 配置pom.xml，指定proto文件

<!-- grpc 依賴jar -->
<dependency>
    <groupId>io.grpc</groupId>
    <artifactId>grpc-netty</artifactId>
    <version>1.3.0</version>
</dependency>
<dependency>
    <groupId>io.grpc</groupId>
    <artifactId>grpc-protobuf</artifactId>
    <version>1.3.0</version>
</dependency>
<dependency>
    <groupId>io.grpc</groupId>
    <artifactId>grpc-stub</artifactId>
    <version>1.3.0</version>
</dependency>

<build>
    <extensions>
        <extension>
            <groupId>kr.motd.maven</groupId>
            <artifactId>os-maven-plugin</artifactId>
            <version>1.4.1.Final</version>
        </extension>
    </extensions>

    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>

        <!-- 根據proto文件生成java -->
        <plugin>
            <groupId>org.xolstice.maven.plugins</groupId>
            <artifactId>protobuf-maven-plugin</artifactId>
            <version>0.5.0</version>
            <configuration>
                <protocArtifact>com.google.protobuf:protoc:3.2.0:exe:${os.detected.classifier}</protocArtifact>
                <pluginId>grpc-java</pluginId>
                <pluginArtifact>io.grpc:protoc-gen-grpc-java:1.3.0:exe:${os.detected.classifier}</pluginArtifact>
                <protoSourceRoot>src/main/resources/com/hry/spring/grpc/simple/</protoSourceRoot>
            </configuration>
            <executions>
                <execution>
                    <goals>
                        <goal>compile</goal>
                        <goal>compile-custom</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>
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b. 執行pom.xml，在target/generated-sources/protobuf/grpc-Java/com/hry/spring/grpc/simple/ 目錄GreeterGrpc.java
GreeterGrpc封裝基本的GRPC功能，后續的客戶端和服務端都從這個類引申出來。GreeterGrpc類見gibhub

2.3 服務端

服務端代碼

public class HelloWorldServer {
    private static final Logger logger = LoggerFactory.getLogger(HelloWorldServer.class);

    private Server server;

    private void start() throws IOException {
        /* The port on which the server should run */
        int port = 50051;
        server = ServerBuilder.forPort(port).addService(new GreeterImpl()).build().start();
        logger.info("Server started, listening on " + port);
        Runtime.getRuntime().addShutdownHook(new Thread() {
            @Override
            public void run() {
                // Use stderr here since the logger may have been reset by its
                // JVM shutdown hook.
                System.err.println("*** shutting down gRPC server since JVM is shutting down");
                HelloWorldServer.this.stop();
                System.err.println("*** server shut down");
            }
        });
    }

    private void stop() {
        if (server != null) {
            server.shutdown();
        }
    }

    /**
     * Await termination on the main thread since the grpc library uses daemon
     * threads.
     */
    private void blockUntilShutdown() throws InterruptedException {
        if (server != null) {
            server.awaitTermination();
        }
    }

    /**
     * Main launches the server from the command line.
     */
    public static void main(String[] args) throws IOException, InterruptedException {
        final HelloWorldServer server = new HelloWorldServer();
        server.start();
        server.blockUntilShutdown();
    }

    static class GreeterImpl extends GreeterGrpc.GreeterImplBase {

        @Override
        public void sayHello(HelloRequest req, StreamObserver<HelloReply> responseObserver) {
            HelloReply reply = HelloReply.newBuilder().setMessage("Hello " + req.getName()).build();
            responseObserver.onNext(reply);
            responseObserver.onCompleted();
        }
    }
}1
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2.4 客戶端

客戶端主代碼

public class HelloWorldClient {
    private static final Logger logger =  LoggerFactory.getLogger(HelloWorldClient.class);
    private final ManagedChannel channel;
    private final GreeterGrpc.GreeterBlockingStub blockingStub;

    /**
     * Construct client connecting to HelloWorld server at {@code host:port}.
     */
    public HelloWorldClient(String host, int port) {
        this(ManagedChannelBuilder.forAddress(host, port)
                // Channels are secure by default (via SSL/TLS). For the example
                // we disable TLS to avoid
                // needing certificates.
                .usePlaintext(true));
    }

    /**
     * Construct client for accessing RouteGuide server using the existing
     * channel.
     */
    HelloWorldClient(ManagedChannelBuilder<?> channelBuilder) {
        channel = channelBuilder.build();
        blockingStub = GreeterGrpc.newBlockingStub(channel);
    }

    public void shutdown() throws InterruptedException {
        channel.shutdown().awaitTermination(5, TimeUnit.SECONDS);
    }

    /** Say hello to server. */
    public void greet(String name) {
        logger.info("Will try to greet " + name + " ...");
        HelloRequest request = HelloRequest.newBuilder().setName(name).build();
        HelloReply response;
        try {
            response = blockingStub.sayHello(request);
        } catch (StatusRuntimeException e) {
            logger.error("RPC failed: {0}", e.getStatus());
            return;
        }
        logger.info("Greeting: " + response.getMessage());
    }

    public static void main(String[] args) throws Exception {
        HelloWorldClient client = new HelloWorldClient("localhost", 50051);
        try {
            String user = "world";
            if (args.length > 0) {
                user = args[0]; 
            }
            client.greet(user);
        } finally {
            client.shutdown();
        }
    }
}1
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2.4 運行

先運行服務端，再運行客戶端，關鍵日志打印如下：

21:35:35.208 [main] INFO com.hry.spring.grpc.simple.HelloWorldClient - Will try to greet world ...

21:35:35.847 [main] INFO com.hry.spring.grpc.simple.HelloWorldClient - Greeting: Hello world1
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