grpc-gateway使用教程

grpc-gateway是go语言的开源项目，涉及到grpc是什么?以及如何在windows使用golang安装grpc可以看下之前写的两篇文章。

[gRPC详细入门介绍]  https://www.cnblogs.com/cxt618/p/15487359.html gRPC详细入门介绍

[windows上使用golang安装grpc]  https://www.cnblogs.com/cxt618/p/15467428.html windows上使用golang安装grpc

1.1 protoc 和 protobuf 参数讲解

按照上面的两篇文章，应该是能安装好protoc和protobuf，由于接下来会使用到protoc，先举例讲解一下：

#!/usr/bin/env bash

protoDir="../proto"
outDir="../proto"

# 编译google.api
protoc -I ${protoDir}/ ${protoDir}/google/api/*.proto \
--go_out ${outDir} \
--go_opt paths=source_relative

# 编译自定义的proto
protoc -I ${protoDir}/ ${protoDir}/*.proto \
--go_out ${outDir}/pb \
--go_opt paths=source_relative \
--go-grpc_out ${outDir}/pb \
--go-grpc_opt paths=source_relative \
--go-grpc_opt require_unimplemented_servers=false \
--grpc-gateway_out ${outDir}/pb \
--grpc-gateway_opt logtostderr=true \
--grpc-gateway_opt paths=source_relative \
--grpc-gateway_opt generate_unbound_methods=true \
--openapiv2_out ${outDir}/pb \
--openapiv2_opt logtostderr=true

参数讲解：

• -I 或者 --proto_path：用于指定所编译的源码，就是我们所导入的proto文件，支持多次指定，按照顺序搜索，如果未指定，则使用当前工作目录。

• --go_out：同样的也有其他语言的，例如--java_out、--csharp_out,用来指定语言的生成位置，用于生成*.pb.go 文件

  • --go_opt：paths=source_relative 指定--go_out生成文件是基于相对路径的

• --go-grpc_out：用于生成 *_grpc.pb.go 文件

• --go-grpc_opt：

  • paths=source_relative 指定--go_grpc_out生成文件是基于相对路径的

  • require_unimplemented_servers=false 默认是true，会在server类多生成一个接口

• --grpc-gateway_out：是使用到了 protoc-gen-grpc-gateway.exe 插件，用于生成pb.gw.go文件

• --grpc-gateway_opt：

  • logtostderr=true 记录log

  • paths=source_relative 指定--grpc-gateway_out生成文件是基于相对路径的

  • generate_unbound_methods=true 如果proto文件没有写api接口信息，也会默认生成

• --openapiv2_out：使用到了protoc-gen-openapiv2.exe 插件，用于生成swagger.json 文件

当然，还有其他很多命令参数，可以使用protoc -help 查看，也提供了很详细的英文提示。

1.2 openssl证书

grpc是使用HTTPS/2协议的，为了方便使用（当然，不用证书也是可以的），我们自制一个CA证书。

1.2.1 生成CA根证书

• 新建ca.conf文件

表示证书配置信息，内容如下：

[ req ]
default_bits       = 4096
distinguished_name = req_distinguished_name
 
[ req_distinguished_name ]
countryName                 = Country Name (2 letter code)
countryName_default         = CN
stateOrProvinceName         = State or Province Name (full name)
stateOrProvinceName_default = GuangDong
localityName                = Locality Name (eg, city)
localityName_default        = ShenZhen
organizationName            = Organization Name (eg, company)
organizationName_default    = Sheld
commonName                  = Common Name (e.g. server FQDN or YOUR name)
commonName_max              = 64
commonName_default          = grpc.demo

• 生成密钥，得到ca.key

openssl genrsa -out ca.key 4096

参数说明：

openssl genrsa：生成RSA私钥，名称为ca.key，4096表示指定生成密钥的位数

• 签发请求，得到ca.csr

openssl req -new -sha256 -out ca.csr -key ca.key -config ca.conf

参数说明：

openssl req：生成签名证书，-new表示生成证书请求，-sha256表示使用sha256加密，-out指定输出证书的名称，-key指定私钥文件，-config指定证书配置的信息

# 输入命令后生成结果如下，因为在ca.conf里面配置了，可以一路next
$ openssl req -new -sha256 -out ca.csr -key ca.key -config ca.conf
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [CN]:
State or Province Name (full name) [GuangDong]:
Locality Name (eg, city) [ShenZhen]:
Organization Name (eg, company) [Sheld]:
Common Name (e.g. server FQDN or YOUR name) [grpc.demo]:

• 生成CA根证书，得到ca.crt

openssl x509 -req -days 3650 -in ca.csr -signkey ca.key -out ca.crt

参数说明：

x509指输出证书，-days 3650为有效期，表示10年

1.2.2 生成终端用户证书

• 新建server.conf

表示证书配置信息，内容如下：

[ req ]
default_bits       = 2048
distinguished_name = req_distinguished_name
req_extensions     = req_ext
 
[ req_distinguished_name ]
countryName                 = Country Name (2 letter code)
countryName_default         = CN
stateOrProvinceName         = State or Province Name (full name)
stateOrProvinceName_default = GuangDong
localityName                = Locality Name (eg, city)
localityName_default        = ShenZhen
organizationName            = Organization Name (eg, company)
organizationName_default    = Sheld
commonName                  = Common Name (e.g. server FQDN or YOUR name)
commonName_max              = 64
commonName_default          = grpc.demo
 
[ req_ext ]
subjectAltName = @alt_names
 
[alt_names]
DNS.1   = grpc.demo
IP      = 127.0.0.1

• 生成密钥，得到server.key

openssl genrsa -out server.key 2048

• 生成证书，签发请求，得到server.csr

openssl req -new -sha256 -out server.csr -key server.key -config server.conf

• 用CA证书生成终端用户证书，得到server.crt

openssl x509 \
  -req \
  -days 3650 \
  -CA ca.crt \
  -CAkey ca.key \
  -CAcreateserial \
  -in server.csr \
  -out server.pem\
  -extensions req_ext \
  -extfile server.conf

二、grpc-gateway的简单使用

本教程示例代码放在这里了：https://gitee.com/pearl-zz/grpc-gateway-demo.git 

2.1 简介及安装使用

简介

grpc-gateway是Google协议缓冲区编译器协议(protoc)的一个插件。它读取protobuf服务定义并生成一个反向代理服务器，该服务器将RESTful HTTP API转换为gRPC。此服务器是根据服务定义中的google.api.http annotations生成的。grpc-gateway能同时提供gRPC和RETSful风格的API。

The gRPC-Gateway is a plugin of the Google protocol buffers compiler protoc. It reads protobuf service definitions and generates a reverse-proxy server which translates a RESTful HTTP API into gRPC. This server is generated according to the google.api.http annotations in your service definitions.

grpc-gateway开源项目地址：https://github.com/grpc-ecosystem/grpc-gateway

grpc-gateway官网文档地址：https://grpc-ecosystem.github.io/grpc-gateway/

grpc-gateway官方示例教程地址：https://grpc-ecosystem.github.io/grpc-gateway/docs/tutorials/

grpc-gateway演示demo地址：https://github.com/iamrajiv/helloworld-grpc-gateway

官方在github上提供了一个helloworld-grpc-gateway demo，非常的简单，大家可以先去看看，就几行代码。

 

上面这张图片，来自官网提供的，简单明了，定义proto文件，然后根据这个proto文件，grpc-gateway帮我们做一层反向代理，整个项目的核心部分——Reverse Proxy。旨在为整个grpc服务提供HTTP+JSON接口，在代码层面生成反向代理只需在服务中进行少量配置以附加HTTP语义。

安装使用

这里使用grpc-gateway的master版本，也就是v2，以前博客的教程可能是v1的，略有不同。

go get -u google.golang.org/grpc/cmd/protoc-gen-go-grpc
go get -u google.golang.org/protobuf/cmd/protoc-gen-go
go get -u github.com/grpc-ecosystem/grpc-gateway
cd $GOPATH/src
go install github.com/grpc-ecosystem/grpc-gateway/protoc-gen-grpc-gateway
go install github.com/grpc-ecosystem/grpc-gateway/protoc-gen-openapiv2

这样，在$GOPATH/bin 目录下就会生成：

protoc-gen-go.exe、protoc-gen-go-grpc.exe、

protoc-gen-grpc-gateway.exe、protoc-gen-openapiv2.exe

注意：grpc-gateway存在两个版本，现在默认的master版本也就是v2

同时，也可以看看github项目上的readme.md文档，里面解释很详细，包含安装步骤和使用指南

 

接下来我们的使用步骤，也基本上是基于官网给出的指导：

  

 

2.2 使用proto定义grpc服务

Define your gRPC service using protocol buffers

与我们之前编写的proto文件略有不同，本次我们需要用到 google/api/annotations.proto 文件。因此，我们可以把annotations.proto文件先下载下来，可以在googleapi项目中下载，路径为：https://github.com/googleapis/googleapis/tree/master/google/api 。本次我们需要使用到 annotations.proto文件，由于annotations.proto又引用到了google/api/http.proto，google/protobuf/descriptor.proto，因此我们把这3个文件一并下载来，并按照目录结构存放。so，先看看本次演示项目的目录结构吧。

如上图所示：项目名为grpc-gateway-demo，在proto文件夹下，HelloWorld.proto 文件是我本次要演示的，同事也建了google文件夹和pb文件夹，其中google文件夹存放了annotations.proto、http.proto以及descriptor.proto文件，pb文件夹是存放我们接下来要生成的pb.go文件。

1. google的proto文件

proto目录中有google/api目录，它用到了google官方提供的两个api描述文件，主要是针对grpc-gateway的http转换提供支持，定义了Protocol Buffer所扩展的HTTP Option.

annotations.proto 文件：

// Copyright (c) 2015, Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

syntax = "proto3";

package google.api;

import "google/api/http.proto";
import "google/protobuf/descriptor.proto";

option go_package = "google.golang.org/genproto/googleapis/api/annotations;annotations";
option java_multiple_files = true;
option java_outer_classname = "AnnotationsProto";
option java_package = "com.google.api";
option objc_class_prefix = "GAPI";

extend google.protobuf.MethodOptions {
// See `HttpRule`.
HttpRule http = 72295728;
}

http.proto文件：

// Copyright 2015 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

syntax = "proto3";

package google.api;

option cc_enable_arenas = true;
option go_package = "google.golang.org/genproto/googleapis/api/annotations;annotations";
option java_multiple_files = true;
option java_outer_classname = "HttpProto";
option java_package = "com.google.api";
option objc_class_prefix = "GAPI";

// Defines the HTTP configuration for an API service. It contains a list of
// [HttpRule][google.api.HttpRule], each specifying the mapping of an RPC method
// to one or more HTTP REST API methods.
message Http {
  // A list of HTTP configuration rules that apply to individual API methods.
  //
  // **NOTE:** All service configuration rules follow "last one wins" order.
  repeated HttpRule rules = 1;

  // When set to true, URL path parameters will be fully URI-decoded except in
  // cases of single segment matches in reserved expansion, where "%2F" will be
  // left encoded.
  //
  // The default behavior is to not decode RFC 6570 reserved characters in multi
  // segment matches.
  bool fully_decode_reserved_expansion = 2;
}

// # gRPC Transcoding
//
// gRPC Transcoding is a feature for mapping between a gRPC method and one or
// more HTTP REST endpoints. It allows developers to build a single API service
// that supports both gRPC APIs and REST APIs. Many systems, including [Google
// APIs](https://github.com/googleapis/googleapis),
// [Cloud Endpoints](https://cloud.google.com/endpoints), [gRPC
// Gateway](https://github.com/grpc-ecosystem/grpc-gateway),
// and [Envoy](https://github.com/envoyproxy/envoy) proxy support this feature
// and use it for large scale production services.
//
// `HttpRule` defines the schema of the gRPC/REST mapping. The mapping specifies
// how different portions of the gRPC request message are mapped to the URL
// path, URL query parameters, and HTTP request body. It also controls how the
// gRPC response message is mapped to the HTTP response body. `HttpRule` is
// typically specified as an `google.api.http` annotation on the gRPC method.
//
// Each mapping specifies a URL path template and an HTTP method. The path
// template may refer to one or more fields in the gRPC request message, as long
// as each field is a non-repeated field with a primitive (non-message) type.
// The path template controls how fields of the request message are mapped to
// the URL path.
//
// Example:
//
//     service Messaging {
//       rpc GetMessage(GetMessageRequest) returns (Message) {
//         option (google.api.http) = {
//             get: "/v1/{name=messages/*}"
//         };
//       }
//     }
//     message GetMessageRequest {
//       string name = 1; // Mapped to URL path.
//     }
//     message Message {
//       string text = 1; // The resource content.
//     }
//
// This enables an HTTP REST to gRPC mapping as below:
//
// HTTP | gRPC
// -----|-----
// `GET /v1/messages/123456`  | `GetMessage(name: "messages/123456")`
//
// Any fields in the request message which are not bound by the path template
// automatically become HTTP query parameters if there is no HTTP request body.
// For example:
//
//     service Messaging {
//       rpc GetMessage(GetMessageRequest) returns (Message) {
//         option (google.api.http) = {
//             get:"/v1/messages/{message_id}"
//         };
//       }
//     }
//     message GetMessageRequest {
//       message SubMessage {
//         string subfield = 1;
//       }
//       string message_id = 1; // Mapped to URL path.
//       int64 revision = 2;    // Mapped to URL query parameter `revision`.
//       SubMessage sub = 3;    // Mapped to URL query parameter `sub.subfield`.
//     }
//
// This enables a HTTP JSON to RPC mapping as below:
//
// HTTP | gRPC
// -----|-----
// `GET /v1/messages/123456?revision=2&sub.subfield=foo` |
// `GetMessage(message_id: "123456" revision: 2 sub: SubMessage(subfield:
// "foo"))`
//
// Note that fields which are mapped to URL query parameters must have a
// primitive type or a repeated primitive type or a non-repeated message type.
// In the case of a repeated type, the parameter can be repeated in the URL
// as `...?param=A&param=B`. In the case of a message type, each field of the
// message is mapped to a separate parameter, such as
// `...?foo.a=A&foo.b=B&foo.c=C`.
//
// For HTTP methods that allow a request body, the `body` field
// specifies the mapping. Consider a REST update method on the
// message resource collection:
//
//     service Messaging {
//       rpc UpdateMessage(UpdateMessageRequest) returns (Message) {
//         option (google.api.http) = {
//           patch: "/v1/messages/{message_id}"
//           body: "message"
//         };
//       }
//     }
//     message UpdateMessageRequest {
//       string message_id = 1; // mapped to the URL
//       Message message = 2;   // mapped to the body
//     }
//
// The following HTTP JSON to RPC mapping is enabled, where the
// representation of the JSON in the request body is determined by
// protos JSON encoding:
//
// HTTP | gRPC
// -----|-----
// `PATCH /v1/messages/123456 { "text": "Hi!" }` | `UpdateMessage(message_id:
// "123456" message { text: "Hi!" })`
//
// The special name `*` can be used in the body mapping to define that
// every field not bound by the path template should be mapped to the
// request body.  This enables the following alternative definition of
// the update method:
//
//     service Messaging {
//       rpc UpdateMessage(Message) returns (Message) {
//         option (google.api.http) = {
//           patch: "/v1/messages/{message_id}"
//           body: "*"
//         };
//       }
//     }
//     message Message {
//       string message_id = 1;
//       string text = 2;
//     }
//
//
// The following HTTP JSON to RPC mapping is enabled:
//
// HTTP | gRPC
// -----|-----
// `PATCH /v1/messages/123456 { "text": "Hi!" }` | `UpdateMessage(message_id:
// "123456" text: "Hi!")`
//
// Note that when using `*` in the body mapping, it is not possible to
// have HTTP parameters, as all fields not bound by the path end in
// the body. This makes this option more rarely used in practice when
// defining REST APIs. The common usage of `*` is in custom methods
// which don't use the URL at all for transferring data.
//
// It is possible to define multiple HTTP methods for one RPC by using
// the `additional_bindings` option. Example:
//
//     service Messaging {
//       rpc GetMessage(GetMessageRequest) returns (Message) {
//         option (google.api.http) = {
//           get: "/v1/messages/{message_id}"
//           additional_bindings {
//             get: "/v1/users/{user_id}/messages/{message_id}"
//           }
//         };
//       }
//     }
//     message GetMessageRequest {
//       string message_id = 1;
//       string user_id = 2;
//     }
//
// This enables the following two alternative HTTP JSON to RPC mappings:
//
// HTTP | gRPC
// -----|-----
// `GET /v1/messages/123456` | `GetMessage(message_id: "123456")`
// `GET /v1/users/me/messages/123456` | `GetMessage(user_id: "me" message_id:
// "123456")`
//
// ## Rules for HTTP mapping
//
// 1. Leaf request fields (recursive expansion nested messages in the request
//    message) are classified into three categories:
//    - Fields referred by the path template. They are passed via the URL path.
//    - Fields referred by the [HttpRule.body][google.api.HttpRule.body]. They are passed via the HTTP
//      request body.
//    - All other fields are passed via the URL query parameters, and the
//      parameter name is the field path in the request message. A repeated
//      field can be represented as multiple query parameters under the same
//      name.
//  2. If [HttpRule.body][google.api.HttpRule.body] is "*", there is no URL query parameter, all fields
//     are passed via URL path and HTTP request body.
//  3. If [HttpRule.body][google.api.HttpRule.body] is omitted, there is no HTTP request body, all
//     fields are passed via URL path and URL query parameters.
//
// ### Path template syntax
//
//     Template = "/" Segments [ Verb ] ;
//     Segments = Segment { "/" Segment } ;
//     Segment  = "*" | "**" | LITERAL | Variable ;
//     Variable = "{" FieldPath [ "=" Segments ] "}" ;
//     FieldPath = IDENT { "." IDENT } ;
//     Verb     = ":" LITERAL ;
//
// The syntax `*` matches a single URL path segment. The syntax `**` matches
// zero or more URL path segments, which must be the last part of the URL path
// except the `Verb`.
//
// The syntax `Variable` matches part of the URL path as specified by its
// template. A variable template must not contain other variables. If a variable
// matches a single path segment, its template may be omitted, e.g. `{var}`
// is equivalent to `{var=*}`.
//
// The syntax `LITERAL` matches literal text in the URL path. If the `LITERAL`
// contains any reserved character, such characters should be percent-encoded
// before the matching.
//
// If a variable contains exactly one path segment, such as `"{var}"` or
// `"{var=*}"`, when such a variable is expanded into a URL path on the client
// side, all characters except `[-_.~0-9a-zA-Z]` are percent-encoded. The
// server side does the reverse decoding. Such variables show up in the
// [Discovery
// Document](https://developers.google.com/discovery/v1/reference/apis) as
// `{var}`.
//
// If a variable contains multiple path segments, such as `"{var=foo/*}"`
// or `"{var=**}"`, when such a variable is expanded into a URL path on the
// client side, all characters except `[-_.~/0-9a-zA-Z]` are percent-encoded.
// The server side does the reverse decoding, except "%2F" and "%2f" are left
// unchanged. Such variables show up in the
// [Discovery
// Document](https://developers.google.com/discovery/v1/reference/apis) as
// `{+var}`.
//
// ## Using gRPC API Service Configuration
//
// gRPC API Service Configuration (service config) is a configuration language
// for configuring a gRPC service to become a user-facing product. The
// service config is simply the YAML representation of the `google.api.Service`
// proto message.
//
// As an alternative to annotating your proto file, you can configure gRPC
// transcoding in your service config YAML files. You do this by specifying a
// `HttpRule` that maps the gRPC method to a REST endpoint, achieving the same
// effect as the proto annotation. This can be particularly useful if you
// have a proto that is reused in multiple services. Note that any transcoding
// specified in the service config will override any matching transcoding
// configuration in the proto.
//
// Example:
//
//     http:
//       rules:
//         # Selects a gRPC method and applies HttpRule to it.
//         - selector: example.v1.Messaging.GetMessage
//           get: /v1/messages/{message_id}/{sub.subfield}
//
// ## Special notes
//
// When gRPC Transcoding is used to map a gRPC to JSON REST endpoints, the
// proto to JSON conversion must follow the [proto3
// specification](https://developers.google.com/protocol-buffers/docs/proto3#json).
//
// While the single segment variable follows the semantics of
// [RFC 6570](https://tools.ietf.org/html/rfc6570) Section 3.2.2 Simple String
// Expansion, the multi segment variable **does not** follow RFC 6570 Section
// 3.2.3 Reserved Expansion. The reason is that the Reserved Expansion
// does not expand special characters like `?` and `#`, which would lead
// to invalid URLs. As the result, gRPC Transcoding uses a custom encoding
// for multi segment variables.
//
// The path variables **must not** refer to any repeated or mapped field,
// because client libraries are not capable of handling such variable expansion.
//
// The path variables **must not** capture the leading "/" character. The reason
// is that the most common use case "{var}" does not capture the leading "/"
// character. For consistency, all path variables must share the same behavior.
//
// Repeated message fields must not be mapped to URL query parameters, because
// no client library can support such complicated mapping.
//
// If an API needs to use a JSON array for request or response body, it can map
// the request or response body to a repeated field. However, some gRPC
// Transcoding implementations may not support this feature.
message HttpRule {
  // Selects a method to which this rule applies.
  //
  // Refer to [selector][google.api.DocumentationRule.selector] for syntax details.
  string selector = 1;

  // Determines the URL pattern is matched by this rules. This pattern can be
  // used with any of the {get|put|post|delete|patch} methods. A custom method
  // can be defined using the 'custom' field.
  oneof pattern {
    // Maps to HTTP GET. Used for listing and getting information about
    // resources.
    string get = 2;

    // Maps to HTTP PUT. Used for replacing a resource.
    string put = 3;

    // Maps to HTTP POST. Used for creating a resource or performing an action.
    string post = 4;

    // Maps to HTTP DELETE. Used for deleting a resource.
    string delete = 5;

    // Maps to HTTP PATCH. Used for updating a resource.
    string patch = 6;

    // The custom pattern is used for specifying an HTTP method that is not
    // included in the `pattern` field, such as HEAD, or "*" to leave the
    // HTTP method unspecified for this rule. The wild-card rule is useful
    // for services that provide content to Web (HTML) clients.
    CustomHttpPattern custom = 8;
  }

  // The name of the request field whose value is mapped to the HTTP request
  // body, or `*` for mapping all request fields not captured by the path
  // pattern to the HTTP body, or omitted for not having any HTTP request body.
  //
  // NOTE: the referred field must be present at the top-level of the request
  // message type.
  string body = 7;

  // Optional. The name of the response field whose value is mapped to the HTTP
  // response body. When omitted, the entire response message will be used
  // as the HTTP response body.
  //
  // NOTE: The referred field must be present at the top-level of the response
  // message type.
  string response_body = 12;

  // Additional HTTP bindings for the selector. Nested bindings must
  // not contain an `additional_bindings` field themselves (that is,
  // the nesting may only be one level deep).
  repeated HttpRule additional_bindings = 11;
}

// A custom pattern is used for defining custom HTTP verb.
message CustomHttpPattern {
  // The name of this custom HTTP verb.
  string kind = 1;

  // The path matched by this custom verb.
  string path = 2;
}

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