GRPC
什么是GRPC?
随着微服务的流行，GRPC的发展势头也越来越盛。我们的后端项目，可能有很多微服务，而这些服务也许是有很多语言写的。比如身份验证的服务是Java,而消息通知的服务是Python，其他业务使用C等等。既然是微服务，我们这些服务之间获取还需要互相调用来协作完成业务，那么不同语言之间如何调用呢？GRPC就是这样的一种通信工具帮助你，让不同语言的程序可以互相交流。不需要你去处理语言之间的障碍，让你看起来就像调用自己写的函数一样简单。
GRPC顾名思义就是远程调用，为什么呢？来自官方文档的一句话：gRPC Remote Procedure Calls。
GRPC与REST的区别
- REST是基于http/1.1,而GRPC是基于http/2。GRPC相对于REST要快很多。
- 消息传输上，REST是JSON/XML，而GRPC是Protobuf,以二进制的形式传输，所以相对于JSON/XML要小很多。
- GRPC API接口是非常严格的，必须明确的在proto文件中定义，REST则无需这样做。
- GRPC代码的生成可以使用协议缓冲区编译器自动生成在GRPC项目内部，而REST需要借助三方工具（Swagger、OpenAPI）
- GRPC可以通信流是双向的，而REST是单向的。
- REST支持浏览器，而GRPC不支持，所以目前RPC 最常用的场景是 IOT 等硬件领域。
使用GRPC的前提
你必须知道以下几个概念
- Protocol Buffers
- 简单流(Unary RPC)
- 客户端流(Server streaming RPC)
- 服务端流(Client streaming RPC)
- 双向流(Bidirectional streaming RPC)
GRPC in Python
下面以简单流为例，其他流可参考官方代码，各种语言的都能在这个仓库找到，routeguide这个示例包含了所有类型的grpc服务。使用注意：使用python开发前你必须安装grpcio-tools、grpcio。
python -m pip install grpcio
python -m pip install grpcio-tools1、编写proto文件
首先根据Protocol Buffers文件，来定义约束我们的服务。我们还是以我们最常见的helloworld为例。在项目根目录下创建文件夹protos，并在该文件夹下创建helloworld.proto文件，内容如下。
syntax = "proto3";
// To be compatible with Java configuration, it does not work in Python
// If false, only a single .java file will be generated for this .proto file.
// If true, separate .java files will be generated for each of the Java classes/enums/etc.
option java_multiple_files = true;
// The package you want to use for your generated Java/Kotlin classes.
option java_package = "com.wangscaler.examples.helloworld";
// The class name (and hence the file name) for the wrapper Java class you want to generate.
option java_outer_classname = "HelloWorldProto";
package helloworld;
// The greeting service definition.
service Greeter {
// Sends a greeting
rpc SayHello (HelloRequest) returns (HelloReply) {}
// Sends another greeting
rpc SayAuthor (AuthorRequest) returns (AuthorReply) {}
}
// The request message containing the user's name.
message HelloRequest {
string name = 1;
}
// The request message containing the user's name.
message AuthorRequest {
string name = 1;
int32 age = 2;
}
// The response message containing the greetings
message HelloReply {
string message = 1;
}
// The response message containing the greetings
message AuthorReply {
string message = 1;
int32 code = 2;
}我们定义了一个Greeter服务，并且这个服务提供了两个接口SayHello和SayAuthor。分别给这两个接口的请求参数和响应参数做了限制。
不同的是SayHello的入参是一个字符串类型的，响应参数也是一个字符串类型的；而AuthorReply入参多了一个int类型的age，而响应参数也多了个int类型的code。
2、自动生成代码
在项目根目录下执行
python -m grpc_tools.protoc -I./protos --python_out=. --grpc_python_out=. ./protos/helloworld.proto执行完之后，会在项目根路径下生成helloworld_pb2.py、helloworld_pb2_grpc.py两个python文件。
3、开发服务端
定义Greeter去继承helloworld_pb2_grpc.GreeterServicer，重写父类的SayHello、SayAuthor来实现我们的业务。
from concurrent import futures
import logging
import grpc
import helloworld_pb2
import helloworld_pb2_grpc
class Greeter(helloworld_pb2_grpc.GreeterServicer):
def SayHello(self, request, context):
print("Get a message from %s client" % request.name)
return helloworld_pb2.HelloReply(message='Hello world, %s client !' % request.name)
def SayAuthor(self, request, context):
print("Hi author(%(name)s), your age is %(age)d" % {"name": request.name, "age": request.age})
return helloworld_pb2.AuthorReply(
message='Hello, %s ! ' % request.name, code=0)
def serve():
server = grpc.server(futures.ThreadPoolExecutor(max_workers=10))
helloworld_pb2_grpc.add_GreeterServicer_to_server(Greeter(), server)
server.add_insecure_port('[::]:50051')
server.start()
server.wait_for_termination()
if __name__ == '__main__':
logging.basicConfig()
serve()
4、开发客户端(python)
import logging
import grpc
import helloworld_pb2
import helloworld_pb2_grpc
def run():
# NOTE(gRPC Python Team): .close() is possible on a channel and should be
# used in circumstances in which the with statement does not fit the needs
# of the code.
with grpc.insecure_channel('localhost:50051') as channel:
stub = helloworld_pb2_grpc.GreeterStub(channel)
hello_response = stub.SayHello(helloworld_pb2.HelloRequest(name='python'))
author_response = stub.SayAuthor(helloworld_pb2.AuthorRequest(name='scaler', age=18))
print("Greeter client received: " + hello_response.message)
print("Greeter client received message: %(message)s and received code: %(code)d !" % {
"message": author_response.message,
"code": author_response.code})
if __name__ == '__main__':
logging.basicConfig()
run()
执行之后控制台打印的消息如下:
Greeter client received: Hello world, python client !
Greeter client received message: Hello, scaler ! and received code: 0 !而我们服务器端的打印消息如下:
Get a message from python client
Hi author(scaler), your age is 18GRPC Java client
一开始我们就说了，GRPC可以兼容多语言的调用，所以我们的java客户端也是可以调用的上面的python的服务器端的SayHello和SayAuthor接口。
1、创建Maven项目
自行使用IDEA创建，不过多介绍。
2、复制上述的proto文件
在maven项目的src/main文件夹下创建proto文件夹，并将上述python中创建的proro文件，复制到这个文件夹下。
3、自动生成代码
使用mvn compile命令，将在target/generated-sources/protobuf/grpc-java和target/generated-sources/protobuf/java生成我们需要的文件。
文件的包名就是我们proto文件中指定的java_package。
4、开发客户端（java）
在src/main/java下创建包和java_package一致，即和生成的代码的包名保持一致。
package com.wangscaler.examples;
import io.grpc.Channel;
import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;
import io.grpc.StatusRuntimeException;
import java.text.MessageFormat;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* @author WangScaler
* @date 2021/7/22 16:36
*/
public class Client {
private static final Logger logger = Logger.getLogger(Client.class.getName());
private final GreeterGrpc.GreeterBlockingStub blockingStub;
public Client(Channel channel) {
blockingStub = GreeterGrpc.newBlockingStub(channel);
}
public void greet(String name) {
logger.info("Will try to greet " + name + " ...");
HelloRequest helloRequest = HelloRequest.newBuilder().setName(name).build();
AuthorRequest authorRequest = AuthorRequest.newBuilder().setName("wangscaler").setAge(18).build();
HelloReply helloResponse;
AuthorReply authorResponse;
try {
helloResponse = blockingStub.sayHello(helloRequest);
authorResponse = blockingStub.sayAuthor(authorRequest);
} catch (StatusRuntimeException e) {
logger.log(Level.WARNING, "RPC failed: {0}", e.getStatus());
return;
}
logger.info("Greeter client received: " + helloResponse.getMessage());
logger.info(MessageFormat.format("Greeter client received message: {0} and received code: {1} ! ", authorResponse.getMessage(), authorResponse.getCode()));
}
public static void main(String[] args) throws Exception {
String user = "java";
String target = "localhost:50010";
if (args.length > 0) {
if ("--help".equals(args[0])) {
System.err.println("Usage: [name [target]]");
System.err.println("");
System.err.println(" name The name you wish to be greeted by. Defaults to " + user);
System.err.println(" target The server to connect to. Defaults to " + target);
System.exit(1);
}
user = args[0];
}
if (args.length > 1) {
target = args[1];
}
ManagedChannel channel = ManagedChannelBuilder.forTarget(target)
.usePlaintext()
.build();
try {
Client client = new Client(channel);
client.greet(user);
} finally {
channel.shutdownNow().awaitTermination(5, TimeUnit.SECONDS);
}
}
}
执行之后控制台打印的消息如下:
信息: Will try to greet java ...
七月 22, 2021 5:00:17 下午 com.wangscaler.examples.Client greet
信息: Greeter client received: Hello world, java client !
七月 22, 2021 5:00:17 下午 com.wangscaler.examples.Client greet
信息: Greeter client received message: Hello, wangscaler ! and received code: 0 ! 而我们python服务器端的打印消息如下:
Get a message from java client
Hi author(wangscaler), your age is 18Cool!我们的Java客户端像调用自己内部的函数一样，调用了远程的python服务器上的方法。这就是GRPC的强大之处。微服务之间的调用就像这一样轻松简单。
使用SSL身份验证
1、生成根证书和私钥
使用openssl生成ssl证书。
openssl req -newkey rsa:2048 -nodes -keyout server.key -x509 -days 365 -out server.crt注意：执行命令之后需要输入你的相关信息，如果你是在ssl本地测试，切记CN的值为localhost，此时你的客户端才可以通过localhost访问你的服务器。
2、修改服务器端
from concurrent import futures
import logging
import grpc
import helloworld_pb2
import helloworld_pb2_grpc
_ONE_DAY_IN_SECONDS = 60 * 60 * 24
class Greeter(helloworld_pb2_grpc.GreeterServicer):
def SayHello(self, request, context):
print("Get a message from %s client" % request.name)
return helloworld_pb2.HelloReply(message='Hello world, %s client !' % request.name)
def SayAuthor(self, request, context):
print("Hi author(%(name)s), your age is %(age)d" % {"name": request.name, "age": request.age})
return helloworld_pb2.AuthorReply(
message='Hello, %s ! ' % request.name, code=0)
def serve():
with open('server.key', 'rb') as f:
private_key = f.read()
with open('server.crt', 'rb') as f:
certificate_chain = f.read()
server_credentials = grpc.ssl_server_credentials(
((private_key, certificate_chain,),))
server = grpc.server(futures.ThreadPoolExecutor(max_workers=10))
helloworld_pb2_grpc.add_GreeterServicer_to_server(Greeter(), server)
server.add_secure_port('[::]:50051', server_credentials)
server.start()
server.wait_for_termination()
if __name__ == '__main__':
logging.basicConfig()
serve()
至此我们的GRPC，就加入了SSL身份验证。
3、修改客户端（python）
我们使用之前的客户端去连接，发现连接失败，如下图所示。
接下来，修改如下：
首先将openssl生成的server.key和server.crt复制到项目的根路径下。最后修改代码如下：
import logging
import grpc
import helloworld_pb2
import helloworld_pb2_grpc
def run():
with open('server.crt', 'rb') as f:
trusted_certs = f.read()
credentials = grpc.ssl_channel_credentials(root_certificates=trusted_certs)
with grpc.secure_channel('localhost:50051', credentials) as channel:
stub = helloworld_pb2_grpc.GreeterStub(channel)
hello_response = stub.SayHello(helloworld_pb2.HelloRequest(name='python'))
author_response = stub.SayAuthor(helloworld_pb2.AuthorRequest(name='scaler', age=18))
print("Greeter client received: " + hello_response.message)
print("Greeter client received message: %(message)s and received code: %(code)d !" % {
"message": author_response.message,
"code": author_response.code})
if __name__ == '__main__':
logging.basicConfig()
run()再次运行客户端，控制台正常打印
Greeter client received: Hello world, python client !
Greeter client received message: Hello, scaler ! and received code: 0 !4、修改客户端（java）
修改之前测试连接。报错如下：
RPC failed: Status{code=UNAVAILABLE, description=Network closed for unknown reason, cause=null}修改如下，将openssl生成的server.crt复制到项目路径下，能找到就可以，不复制也行。
package com.wangscaler.examples;
import io.grpc.Channel;
import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;
import io.grpc.StatusRuntimeException;
import io.grpc.netty.shaded.io.grpc.netty.GrpcSslContexts;
import io.grpc.netty.shaded.io.grpc.netty.NegotiationType;
import io.grpc.netty.shaded.io.grpc.netty.NettyChannelBuilder;
import io.grpc.netty.shaded.io.netty.handler.ssl.SslContext;
import io.grpc.netty.shaded.io.netty.handler.ssl.SslContextBuilder;
import javax.net.ssl.SSLException;
import java.io.File;
import java.text.MessageFormat;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* @author WangScaler
* @date 2021/7/22 16:36
*/
public class Client {
private static final Logger logger = Logger.getLogger(Client.class.getName());
private final GreeterGrpc.GreeterBlockingStub blockingStub;
public Client(Channel channel) {
blockingStub = GreeterGrpc.newBlockingStub(channel);
}
public void greet(String name) {
logger.info("Will try to greet " + name + " ...");
HelloRequest helloRequest = HelloRequest.newBuilder().setName(name).build();
AuthorRequest authorRequest = AuthorRequest.newBuilder().setName("wangscaler").setAge(18).build();
HelloReply helloResponse;
AuthorReply authorResponse;
try {
helloResponse = blockingStub.sayHello(helloRequest);
authorResponse = blockingStub.sayAuthor(authorRequest);
} catch (StatusRuntimeException e) {
logger.log(Level.WARNING, "RPC failed: {0}", e.getStatus());
return;
}
logger.info("Greeter client received: " + helloResponse.getMessage());
logger.info(MessageFormat.format("Greeter client received message: {0} and received code: {1} ! ", authorResponse.getMessage(), authorResponse.getCode()));
}
private static SslContext buildSslContext(String trustCertCollectionFilePath) throws SSLException {
SslContextBuilder builder = GrpcSslContexts.forClient();
if (trustCertCollectionFilePath != null) {
builder.trustManager(new File(trustCertCollectionFilePath));
}
return builder.build();
}
public static void main(String[] args) throws Exception {
String user = "java";
String target = "localhost:50010";
if (args.length > 0) {
if ("--help".equals(args[0])) {
System.err.println("Usage: [name [target]]");
System.err.println("");
System.err.println(" name The name you wish to be greeted by. Defaults to " + user);
System.err.println(" target The server to connect to. Defaults to " + target);
System.exit(1);
}
user = args[0];
}
if (args.length > 1) {
target = args[1];
}
String[] targets = new String[2];
targets = target.split(":");
String host = targets[0];
int port = Integer.parseInt(targets[1]);
SslContext sslContext = Client.buildSslContext("D://springboot/test-grpc/src/main/java/com/wangscaler/examples/server.crt");
ManagedChannel channel = NettyChannelBuilder.forAddress(host, port)
.negotiationType(NegotiationType.TLS)
.sslContext(sslContext)
.build();
try {
Client client = new Client(channel);
client.greet(user);
} finally {
channel.shutdownNow().awaitTermination(5, TimeUnit.SECONDS);
}
}
}
再次连接。控制台正常的调用到服务器端的函数。
信息: Will try to greet java ...
七月 27, 2021 9:38:51 上午 com.wangscaler.examples.Client greet
信息: Greeter client received: Hello world, java client !
七月 27, 2021 9:38:51 上午 com.wangscaler.examples.Client greet
信息: Greeter client received message: Hello, wangscaler ! and received code: 0 ! 参考信息
- [1] grpc.io
- [2] grpc example
- [3] Using SSL with gRPC in Python
- [4] ssl_grpc_example
