How to use Spring Boot+gRPC to build and deploy microservices

1. Why use Istio?

Currently, for the Java technology stack, the best choice for building microservices is Spring Boot, and Spring Boot is generally used with the microservice framework Spring Cloud, which has many implementation cases.

Spring Cloud seems perfect, but after actual development, it is easy to find that Spring Cloud has the following serious problems:

• Service governance related Logic exists in SDKs such as Spring Cloud Netflix and is tightly coupled with business code.

• The SDK is too intrusive to the business code. When the SDK is upgraded and cannot be backward compatible, the business code must be changed to adapt to the SDK upgrade - even if the business logic does not Nothing has changed.

• The various components are dazzling, the quality is also uneven, the learning cost is too high, and it is difficult to completely reuse the code between components. It is also difficult to learn the SDK just to implement governance logic. Not a very good choice.

• is bound to the Java technology stack. Although other languages ​​​​can be connected, the logic related to service governance must be manually implemented, which does not comply with the principle of microservices "can be developed in multiple languages" .

• Spring Cloud is just a development framework and does not implement the service scheduling, resource allocation and other functions necessary for microservices. These requirements must be completed with the help of platforms such as Kubernetes. Spring Cloud and Kubernetes have overlapping functionality, and conflicting features create difficulties in smooth collaboration between the two..

Are there any alternatives to Spring Cloud? have! It is Istio.

Istio completely separates the governance logic from the business code and implements an independent process (Sidecar). During deployment, Sidecar and business code coexist in the same Pod, but the business code is completely unaware of the existence of Sidecar. This achieves zero intrusion of governance logic into business code - in fact, not only is the code not intrusive, there is no coupling between the two at runtime. This allows different microservices to be developed using different languages ​​and technology stacks without having to worry about service governance issues. It can be said that this is a very elegant solution.

So, the question of "Why use Istio" is easily solved - because Istio solves the pain points of traditional microservices such as the coupling of business logic and service governance logic, and the inability to achieve cross-language well. And very easy to use. Learning how to use Istio is not difficult once you master Kubernetes.

1.1. Why use gRPC as a communication framework?

In the microservice architecture, communication between services is a relatively big problem, and is generally implemented using RPC or RESTful API.

Spring Boot can use RestTemplate to call remote services, but this method is not intuitive and the code is complicated. Cross-language communication is also a big problem; gRPC is more convenient than common Java RPC frameworks such as Dubbo. It is lightweight, easy to use, has high code readability, and can be well integrated with Istio and Kubernetes. With the support of Protobuf and HTTP2, its performance is also pretty good, so this time gRPC was chosen to solve the Spring Boot microprocessor problem. Inter-service communication issues. Moreover, although gRPC does not have service discovery, load balancing and other capabilities, Istio is very powerful in this regard, and the two form a perfect complementary relationship.

Considering that various grpc-spring-boot-starters may have unknown side effects on the integration of Spring Boot and Istio, I did not use any grpc-spring-boot-starter this time. The integration of gRPC and Spring Boot was directly handwritten. If you don't want to use a third-party framework to integrate gRPC and Spring Boot, you can refer to my simple implementation method.

1.2. Write business code

First use Spring Initializr to establish the parent project spring-boot-istio and introduce gRPC dependencies. The pom file is as follows:

<?xml version="1.0" encoding="UTF-8"?>
    <project xmlns="http://maven.apache.org/POM/4.0.0" 
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <modules>
        <module>spring-boot-istio-api</module>
        <module>spring-boot-istio-server</module>
        <module>spring-boot-istio-client</module>
    </modules>
    <parent>
        <groupId>org.springframework.boot</groupId> 
       <artifactId>spring-boot-starter-parent</artifactId> 
       <version>2.2.6.RELEASE</version>
       <relativePath/>
     </parent>
    <groupId>site.wendev</groupId>
    <artifactId>spring-boot-istio</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>spring-boot-istio</name>
    <description>Demo project for Spring Boot With Istio.</description>
    <packaging>pom</packaging>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>io.grpc</groupId>
                <artifactId>grpc-all</artifactId>
                <version>1.28.1</version>
            </dependency>
        </dependencies>
    </dependencyManagement>
</project>

Then create the public dependency module spring-boot-istio-api. The pom file is as follows, mainly some dependencies of gRPC:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>spring-boot-istio</artifactId>
        <groupId>site.wendev</groupId>
        <version>0.0.1-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>
    <artifactId>spring-boot-istio-api</artifactId>
    <dependencies>
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-all</artifactId>
        </dependency>
        <dependency>
            <groupId>javax.annotation</groupId>
            <artifactId>javax.annotation-api</artifactId>
            <version>1.3.2</version> 
       </dependency>
    </dependencies> 
   <build>
        <extensions>
            <extension>
                <groupId>kr.motd.maven</groupId>
                <artifactId>os-maven-plugin</artifactId>
                <version>1.6.2</version>
            </extension>
        </extensions>
        <plugins>
            <plugin> 
               <groupId>org.xolstice.maven.plugins</groupId>
                <artifactId>protobuf-maven-plugin</artifactId>
                <version>0.6.1</version>
                <configuration>
                    <protocArtifact>com.google.protobuf:protoc:3.11.3:exe:${os.detected.classifier}</protocArtifact>
                    <pluginId>grpc-java</pluginId>
                    <pluginArtifact>io.grpc:protoc-gen-grpc-java:1.28.1:exe:${os.detected.classifier}</pluginArtifact>
                    <protocExecutable>/Users/jiangwen/tools/protoc-3.11.3/bin/protoc</protocExecutable>
                </configuration>
                <executions>
                    <execution>
                        <goals>
                            <goal>compile</goal>
                            <goal>compile-custom</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

Create the src/main/proto folder , create hello.proto in this folder, and define the interface between services as follows:

syntax = "proto3";
option java_package = "site.wendev.spring.boot.istio.api";
option java_outer_classname = "HelloWorldService";
package helloworld;

service HelloWorld {
    rpc SayHello (HelloRequest)
 returns (HelloResponse) {}
}

message HelloRequest {
    string name = 1;
}
message HelloResponse {
    string message = 1;
}

It is very simple, just send a name and return a message with name.

Then generate the server and client codes and put them in the java folder. For this part, you can refer to the official documentation of gRPC.

Once the API module is available, service providers (servers) and service consumers (clients) can be developed. Here we focus on how to integrate gRPC and Spring Boot.

1) The server side

The business code is very simple:

/**
 * 服务端业务逻辑实现
 * 
 * @author 江文
 * @date 2020/4/12 2:49 下午
 */
@Slf4j
@Component
public class HelloServiceImpl extends HelloWorldGrpc.HelloWorldImplBase {
    @Override
    public void sayHello(HelloWorldService.HelloRequest request,
                         StreamObserver<HelloWorldService.HelloResponse> responseObserver) {
        // 根据请求对象建立响应对象，返回响应信息
        HelloWorldService.HelloResponse response = HelloWorldService.HelloResponse
                .newBuilder()
                .setMessage(String.format("Hello, %s. This message comes from gRPC.", request.getName()))
                .build();
        responseObserver.onNext(response);
        responseObserver.onCompleted();
        log.info("Client Message Received：[{}]", request.getName());
    }
}

In addition to the business code, we also need to start gRPC at the same time when the application starts Server. First, write the startup, shutdown and other logic on the server side:

/**
 * gRPC Server的配置——启动、关闭等
 * 需要使用<code>@Component</code>注解注册为一个Spring Bean
 * 
 * @author 江文
 * @date 2020/4/12 2:56 下午
 */
@Slf4j
@Componentpublic class GrpcServerConfiguration {
    @Autowired
    HelloServiceImpl service;
    /** 注入配置文件中的端口信息 */ 
   @Value("${grpc.server-port}")
    private int port;
    private Server server;
    public void start() throws IOException {
        // 构建服务端
        log.info("Starting gRPC on port {}.", port);
        server = ServerBuilder.forPort(port).addService(service).build().start();
        log.info("gRPC server started, listening on {}.", port);
        // 添加服务端关闭的逻辑
        Runtime.getRuntime().addShutdownHook(new Thread(() -> {
            log.info("Shutting down gRPC server.");
            GrpcServerConfiguration.this.stop();
            log.info("gRPC server shut down successfully.");
        }));
    }
    private void stop() {
        if (server != null) {
            // 关闭服务端
            server.shutdown();
        }
    }
    public void block() throws InterruptedException {
        if (server != null) {
            // 服务端启动后直到应用关闭都处于阻塞状态，方便接收请求 
           server.awaitTermination();
        }
    }
}

After defining the startup, stop and other logic of gRPC, you can use CommandLineRunner to add it to the startup of Spring Boot:

/** 
 * 加入gRPC Server的启动、停止等逻辑到Spring Boot的生命周期中
 *
 * @author 江文
 * @date 2020/4/12 3:10 下午
 */
@Component
public class GrpcCommandLineRunner implements CommandLineRunner {
    @Autowired
    GrpcServerConfiguration configuration;

    @Override
    public void run(String... args) throws Exception {
        configuration.start();
        configuration.block();
    }
}

We register gRPC logic as Spring Bean because we need to obtain its instance and perform corresponding operations.

In this way, when starting Spring Boot, due to the existence of CommandLineRunner, the gRPC server can be started at the same time.

2) The client

business code is also very simple:

/**
 * 客户端业务逻辑实现
 *
 * @author 江文
 * @date 2020/4/12 3:26 下午
 */
@RestController
@Slf4j
public class HelloController {
    @Autowired
    GrpcClientConfiguration configuration;
    @GetMapping("/hello")
    public String hello(@RequestParam(name = "name", defaultValue = "JiangWen", required = false) String name) {
        // 构建一个请求        HelloWorldService.HelloRequest request = HelloWorldService.HelloRequest
                .newBuilder()
                .setName(name)
                .build();        // 使用stub发送请求至服务端
        HelloWorldService.HelloResponse response = configuration.getStub().sayHello(request);
        log.info("Server response received: [{}]", response.getMessage());
        return response.getMessage();
    }
}

在启动客户端时，我们需要打开gRPC的客户端，并获取到channel和stub以进行RPC通信，来看看gRPC客户端的实现逻辑：

/**
 * gRPC Client的配置——启动、建立channel、获取stub、关闭等
 * 需要注册为Spring Bean
 *
 * @author 江文
 * @date 2020/4/12 3:27 下午
 */
@Slf4j
@Component
public class GrpcClientConfiguration {
    /** gRPC Server的地址 */
    @Value("${server-host}")
    private String host;
    /** gRPC Server的端口 */
    @Value("${server-port}")
    private int port;
    private ManagedChannel channel;
    private HelloWorldGrpc.HelloWorldBlockingStub stub;
    public void start() {
        // 开启channel
        channel = ManagedChannelBuilder.forAddress(host, port).usePlaintext().build();
        // 通过channel获取到服务端的stub
        stub = HelloWorldGrpc.newBlockingStub(channel);
        log.info("gRPC client started, server address: {}:{}", host, port);
    }
    public void shutdown() throws InterruptedException {
        // 调用shutdown方法后等待1秒关闭channel
        channel.shutdown().awaitTermination(1, TimeUnit.SECONDS);
        log.info("gRPC client shut down successfully.");
    }
    public HelloWorldGrpc.HelloWorldBlockingStub getStub() {
        return this.stub;
    }
}

比服务端要简单一些。

最后，仍然需要一个CommandLineRunner把这些启动逻辑加入到Spring Boot的启动过程中：

/**
 * 加入gRPC Client的启动、停止等逻辑到Spring Boot生命周期中
 *
 * @author 江文
 * @date 2020/4/12 3:36 下午
 */
@Component
@Slf4j
public class GrpcClientCommandLineRunner implements CommandLineRunner {
    @Autowired
    GrpcClientConfiguration configuration;

    @Override
    public void run(String... args) {
        // 开启gRPC客户端
        configuration.start();
                // 添加客户端关闭的逻辑
        Runtime.getRuntime().addShutdownHook(new Thread(() -> {
            try {
                configuration.shutdown();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }));
    }
}

1.3､ 编写Dockerfile

业务代码跑通之后，就可以制作Docker镜像，准备部署到Istio中去了。

在开始编写Dockerfile之前，先改动一下客户端的配置文件：

server:
  port: 19090
spring:
  application:
      name: spring-boot-istio-clientserver-host: ${server-host}server-port: ${server-port}

接下来编写Dockerfile：

1) 服务端：

FROM openjdk:8u121-jdk
RUN /bin/cp /usr/share/zoneinfo/Asia/Shanghai /etc/localtime \
  && echo 'Asia/Shanghai' >/etc/timezone
ADD /target/spring-boot-istio-server-0.0.1-SNAPSHOT.jar /ENV
 SERVER_PORT="18080" ENTRYPOINT java -jar /spring-boot-istio-server-0.0.1-SNAPSHOT.jar

主要是规定服务端应用的端口为18080，并且在容器启动时让服务端也一起启动。

2) 客户端：

FROM openjdk:8u121-jdk
RUN /bin/cp /usr/share/zoneinfo/Asia/Shanghai /etc/localtime \
  && echo 'Asia/Shanghai' >/etc/timezoneADD /target/spring-boot-istio-client-0.0.1-SNAPSHOT.jar /ENV GRPC_SERVER_HOST="spring-boot-istio-server"ENV GRPC_SERVER_PORT="18888"ENTRYPOINT java -jar /spring-boot-istio-client-0.0.1-SNAPSHOT.jar \ --server-host=$GRPC_SERVER_HOST \ --server-port=$GRPC_SERVER_PORT

可以看到这里添加了启动参数，配合前面的配置，当这个镜像部署到Kubernetes集群时，就可以在Kubernetes的配合之下通过服务名找到服务端了。

同时，服务端和客户端的pom文件中添加：

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <executable>true</executable>
                </configuration>
            </plugin>
            <plugin>
                <groupId>com.spotify</groupId> 
               <artifactId>dockerfile-maven-plugin</artifactId>
                <version>1.4.13</version>
                <dependencies>
                    <dependency>
                        <groupId>javax.activation</groupId>
                        <artifactId>activation</artifactId>
                        <version>1.1</version>
                    </dependency>
                </dependencies>
                <executions>
                    <execution>
                        <id>default</id> 
                       <goals>
                            <goal>build</goal>
                            <goal>push</goal>
                       </goals>
                    </execution>
                </executions>
                <configuration>
                    <repository>wendev-docker.pkg.coding.net/develop/docker/${project.artifactId}</repository>
                    <tag>${project.version}</tag>
                    <buildArgs>
                        <JAR_FILE>${project.build.finalName}.jar</JAR_FILE>
                    </buildArgs>
                </configuration>
            </plugin>
        </plugins>
    </build>

这样执行mvn clean package时就可以同时把docker镜像构建出来了。

2. 编写部署文件

有了镜像之后，就可以写部署文件了：

1) 服务端：

apiVersion: v1
kind:
 Servicemetadata:
  name: spring-boot-istio-server
spec:
  type: ClusterIP
  ports:
    - name: http 
      port: 18080
      targetPort: 18080
    - name: grpc
      port: 18888
      targetPort: 18888
  selector:
    app: spring-boot-istio-server

---apiVersion: apps/v1
kind:
 Deploymentmetadata:
  name: spring-boot-istio-server
spec:
  replicas: 1
  selector:
    matchLabels:
      app: spring-boot-istio-server
  template:
    metadata:
      labels:
        app: spring-boot-istio-server
    spec:
      containers:
        - name: spring-boot-istio-server
          image: wendev-docker.pkg.coding.net/develop/docker/spring-boot-istio-server:0.0.1-SNAPSHOT
          imagePullPolicy: Always
          tty: true
          ports:
            - name: http
              protocol: TCP
              containerPort: 18080 
            - name: grpc
              protocol: TCP
              containerPort: 18888

主要是暴露服务端的端口：18080和gRPC Server的端口18888，以便可以从Pod外部访问服务端。

2) 客户端：

apiVersion: v1
kind:
 Servicemetadata:
  name:
 spring-boot-istio-client
spec:
  type: ClusterIP
  ports:
    - name: http
      port: 19090
      targetPort: 19090
  selector:
    app: spring-boot-istio-client

---apiVersion: apps/v1
kind:
 Deploymentmetadata:
  name: spring-boot-istio-client
spec:
  replicas: 1
  selector:
    matchLabels:
      app: spring-boot-istio-client
  template:
    metadata:
      labels:
        app: spring-boot-istio-client
    spec:
      containers:
        - name: spring-boot-istio-client
          image: wendev-docker.pkg.coding.net/develop/docker/spring-boot-istio-client:0.0.1-SNAPSHOT
          imagePullPolicy: Always
          tty: true
          ports:
            - name: http 
             protocol: TCP
              containerPort: 19090

主要是暴露客户端的端口19090，以便访问客户端并调用服务端。

如果想先试试把它们部署到k8s可不可以正常访问，可以这样配置Ingress：

apiVersion: networking.k8s.io/v1beta1
kind:
 Ingressmetadata:
  name: nginx-web
  annotations:
    kubernetes.io/ingress.class: "nginx"
    nginx.ingress.kubernetes.io/use-reges: "true"
    nginx.ingress.kubernetes.io/proxy-connect-timeout: "600"
    nginx.ingress.kubernetes.io/proxy-send-timeout: "600"
    nginx.ingress.kubernetes.io/proxy-read-timeout: "600"
    nginx.ingress.kubernetes.io/proxy-body-size: "10m"
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  rules:
    - host: dev.wendev.site
      http:
        paths:
          - path: /
            backend:
              serviceName: spring-boot-istio-client
              servicePort: 19090

Istio的网关配置文件与k8s不大一样：

apiVersion: networking.istio.io/v1alpha3
kind:
 Gatewaymetadata:
  name: spring-boot-istio-gateway
spec:
  selector:
    istio: ingressgateway
  servers:
    - port:
        number: 80
        name: http
        protocol: HTTP
      hosts:
        - "*"

---apiVersion: networking.istio.io/v1alpha3
kind: Virtual
Servicemetadata:
  name: spring-boot-istio
spec:
  hosts:
    - "*"
  gateways:
    - spring-boot-istio-gateway
  http:
    - match:
        - uri:
            exact: /hello
      route:
        - destination:
            host: spring-boot-istio-client
            port:
              number: 19090

主要就是暴露/hello这个路径，并且指定对应的服务和端口。

3. 部署应用到Istio

首先搭建k8s集群并且安装istio。我使用的k8s版本是1.16.0，Istio版本是最新的1.6.0-alpha.1，使用istioctl命令安装Istio。建议跑通官方的bookinfo示例之后再来部署本项目。

注：以下命令都是在开启了自动注入Sidecar的前提下运行的

我是在虚拟机中运行的k8s，所以istio-ingressgateway没有外部ip：

$ kubectl get svc istio-ingressgateway -n istio-system
NAME                   TYPE       CLUSTER-IP      EXTERNAL-IP   PORT(S) 
                                                                                                                                     
AGEistio-ingressgateway   NodePort   10.97.158.232   <none>        15020:30388/TCP,80:31690/TCP,443:31493/TCP,15029:32182/TCP,15030:31724/TCP,15031:30887/TCP,15032:30369/TCP,31400:31122/TCP,15443:31545/TCP   26h

所以，需要设置IP和端口，以NodePort的方式访问gateway：

export INGRESS_PORT=$(kubectl -n istio-system get service istio-ingressgateway -o jsonpath='{.spec.ports[?(@.name=="http2")].nodePort}')
export SECURE_INGRESS_PORT=$(kubectl -n istio-system get service istio-ingressgateway -o jsonpath='{.spec.ports[?(@.name=="https")].nodePort}')
export INGRESS_HOST=127.0.0.1export GATEWAY_URL=$INGRESS_HOST:$INGRESS_PORT

这样就可以了。

接下来部署服务：

$ kubectl apply -f spring-boot-istio-server.yml
$ kubectl apply -f spring-boot-istio-client.yml
$ kubectl apply -f istio-gateway.yml

必须要等到两个pod全部变为Running而且Ready变为2/2才算部署完成。

接下来就可以通过

curl -s http://${GATEWAY_URL}/hello

访问到服务了。如果成功返回了Hello, JiangWen. This message comes from gRPC.的结果，没有出错则说明部署完成。

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