gRPC SkyLB

gRPC 作为一款高性能、通用的 RPC 框架，相比传统的RPC框架有着自己天然的优势：

protobuf二进制消息，性能好/效率高（空间和时间效率都很不错）；
proto文件生成目标代码，简单易用；
序列化反序列化直接对应程序中的数据类，不需要解析后在进行映射(XML,JSON都是这种方式)；
支持向前兼容（新加字段采用默认值）和向后兼容（忽略新加字段），简化升级；
支持多种语言（可以把proto文件看做IDL文件）；
Netty等一些框架集成；

服务注册/发现是RPC框架的核心组件，但是gRPC 作为企业级框架，他的开源组件官方并未直接提供服务注册与发现的功能实现。而是在设计文档(load-balancing.md)中提供了实现的思路，并在不同语言的gRPC代码API中提供了命名解析和负载均衡接口供扩展。

关于gRPC 服务发现&负载均衡的介绍，可以参见我之前写的一篇文章 gRPC服务发现&负载均衡

Overview

gRPC SkyLB 采用独立LB进程（External Load Balancing Service）负载均衡方式，支持轮询、一致性哈希两种负载均衡策略，并支持服务端权重。采用etcd作为注册中心。

项目地址：

https://github.com/binchencoder/grpc-skylb

Architecture of SkyLB

服务提供者起来后向注册中心(SkyLB) 注册自己的信息，ip、端口、权重等，并保持心跳。客户端监听注册中心，获取服务器列表，一旦服务器发生变化，客户端马上更新本地的服务器列表。客户端每个请求都通过负载均衡策略选择一个合适的服务器去访问。

Usage

Dependency

Install skylb-client local repository

1	chenbindeMacBook-Pro:grpc-skylb chenbin$ mvn clean install

<dependency>
	<groupId>com.binchencoder.skylb</groupId>
	<artifactId>skylb-client</artifactId>
	<version>1.0-SNAPSHOT</version>
</dependency>

Implements gRPC API

public class DemoGrpcImpl extends DemoGrpc.DemoImplBase {
  private final Logger LOGGER = LoggerFactory.getLogger(DemoGrpcImpl.class);

  private Random rand = new Random(System.currentTimeMillis());
  private int port;
  public DemoGrpcImpl(int port_) {
    this.port = port_;
  }

  @Override
  public void greeting(GreetingProtos.GreetingRequest request,
      StreamObserver<GreetingProtos.GreetingResponse> responseObserver) {
    LOGGER.info("Got req: {}", request);

    // 随机耗时350~550毫秒.
    int elapse = 350 + rand.nextInt(200);
    try {
      TimeUnit.MILLISECONDS.sleep(elapse);
    } catch (InterruptedException ie) {
      LOGGER.warn("sleep interrupted");
    }

    GreetingResponse reply = GreetingResponse.newBuilder().setGreeting(
        "Hello " + request.getName() + ", from :" + port + ", elapse " + elapse + "ms").build();
    responseObserver.onNext(reply);
    responseObserver.onCompleted();
  }

  @Override
  public void greetingForEver(GreetingProtos.GreetingRequest request,
      StreamObserver<GreetingProtos.GreetingResponse> responseObserver) {
    super.greetingForEver(request, responseObserver);
  }
}

Server server = ServerTemplate.create(
			{port} 9090, 
			{bindableService} new DemoGrpcImpl(), 
			{serviceName} "shared-test-client-service")
  .build()
  .start();

SkyLBServiceReporter reporter = ServerTemplate.reportLoad(
			{skylbUri} "skylb://127.0.0.1:1900/",
			{serviceName} ServiceNameUtil.toString(ServiceId.CUSTOM_EASE_GATEWAY_TEST),
			{portName} "grpc",
			{port} 9090);

Call gRPC Server

Create gRPC Stub

ManagedChannel channel = ClientTemplate.createChannel(
			{skylbAddr} "skylb://127.0.0.1:1900/",
			{calleeServiceName} ServiceNameUtil.toString(ServiceId.CUSTOM_EASE_GATEWAY_TEST),
			{calleePortName} "grpc", 
			{calleeNamespace} null,                                   
			{callerServiceName} ServiceNameUtil.toString(ServiceId.SERVICE_NONE)).getOriginChannel();

DemoGrpc.DemoBlockingStub blockingStub = DemoGrpc.newBlockingStub(channel);

GreetingRequest request = GreetingRequest.newBuilder()
  .setName("GC " + Calendar.getInstance().get(Calendar.SECOND))
  .build();
GreetingResponse response = blockingStub
  .withDeadlineAfter(2000, TimeUnit.MILLISECONDS)
  .greeting(request);

Run Demo

Build SkyLB Server

1 2	chenbindeMacBook-Pro:grpc-skylb chenbin$ cd skylb-server chenbindeMacBook-Pro:skylb-server chenbin$ mvn clean package

最终skylb.jar 打包到 skylb-server/target 目录下

Start SkyLB Server

Start ETCD3

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yum install etcd -y

systemctl enable etcd && systemctl start etcd

NOTE

部署ETCD遇到问题可参考 https://www.cnblogs.com/shawhe/p/10640820.html

chenbindeMacBook-Pro:skylb-server chenbin$ cd target/skylblib

chenbindeMacBook-Pro:skylblib chenbin$ java -jar skylb.jar -h
	Usage: java -jar skylb.jar [options] [command] [command options]
  Options:
    --auto-disconn-timeout, -auto-disconn-timeout
      The timeout to automatically disconnect the resolve RPC. e.g. 10s(10 
      Seconds), 10m(10 Minutes)
      Default: PT5M
  Commands:
    etcd      Help for etcd options
      Usage: etcd [options]
        Options:
          --etcd-endpoints, -etcd-endpoints
            The comma separated ETCD endpoints. e.g., 
            http://etcd1:2379,http://etcd2:2379 
            Default: [http://127.0.0.1:2379]
          --etcd-key-ttl, -etcd-key-ttl
            The etcd key time-to-live. e.g. 10s(10 Seconds), 10m(10 Minutes)
            Default: PT10S

chenbindeMacBook-Pro:skylblib chenbin$ java -jar skylb.jar -etcd-endpoints=http://127.0.0.1:2379

Start gRPC Server

https://github.com/binchencoder/grpc-skylb/blob/master/examples/demo/src/main/java/com/binchencoder/skylb/demo/grpc/server/GreetingServer.java

Run com/binchencoder/skylb/demo/grpc/server/GreetingServer#main
Start gRPC Client

https://github.com/binchencoder/grpc-skylb/blob/master/examples/demo/src/main/java/com/binchencoder/skylb/demo/grpc/client/GreetingClient.java

Run com/binchencoder/skylb/demo/grpc/client/GreetingClient#main

More Examples

grpc-skylb/examples/echo

该示例采用SpringBoot脚手架，在spring-boot-grpc-common.jar中封装好了注册服务的逻辑，启动方式比较简单

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@GrpcService(applyGlobalInterceptors = true) // Default use Global Interceptor
public class EchoGrpcService extends EchoServiceGrpc.EchoServiceImplBase {
}

使用@GrpcService 注解方式标示gRPC Service
在 spring-boot-grpc-common.jar 中默认配置两个Global Interceptor(ExceptionInterceptor, AuthenticationInterceptor)

使用者可通过注解不使用Global Interceptor，实现自己的Interceptor

1	@GrpcService(applyGlobalInterceptors = false, interceptors = ExceptionInterceptor.class)

Features

@GrpcService Annotation
支持配置全局拦截器
将来计划支持skylb-client Golang版本

小时候，哭是我们解决问题的绝招。长大后，笑是我们面对现实的武器。

gRPC SkyLB (an gRPC load balancer based on External Load Balancing Service)