再探 gRPC 在 ASP.NET Core 7 的 JSON 轉碼功能

之前筆記 gRPC 在 ASP.NET Core 7 的 JSON 轉碼功能 紀錄到如何使用 ASP.NET Core 7 加入的 JSON 轉碼功能：可以讓 gRPC service 也可以透過 rest api 的方式來呼叫。

不過眼尖的人一定也發現了，呼叫 gRPC service 與呼叫 rest api 的內容有些不同，雖然 response 一致，但是 request 卻差了許多：

  1. service 的 endpoint

    除了 protocol 不同之外，rest api 還包含了 path 及 parameter

    • gRPC

      grpc://localhost:7156

    • rest api

      https://localhost:7156/v1/greeter/name

  2. request 的 parameter 傳遞方式

    • gRPC

      {
  "name": "gRPC"
}

    • rest api

      url parameter : https://localhost:7156/v1/greeter/{name}

今天打算來嘗試將 gRPC 與 rest api 的使用體驗調整的接近些，因為團隊主要的開發環境是 macOS 所以會基於 gRPC 在 ASP.NET Core 7 的 JSON 轉碼功能 (macOS) 來延伸設定，不過差異並不大 (只差在 appsettings.json 中 Kestrel 的 Endpoints 部份)

基本環境說明

  1. macOS Ventura 13.2
  2. .NET SDK 7.0.203

  3. JetBrains Rider 2023.1

    使用 gRPC service 預設專案範本

  4. NuGet packages

    • Microsoft.AspNetCore.Grpc.JsonTranscoding 7.0.5

設定方式

前三點皆與 gRPC 在 ASP.NET Core 7 的 JSON 轉碼功能 (macOS) 相同

  1. 將 NuGet package Microsoft.AspNetCore.Grpc.JsonTranscoding 加入 project

  2. 註冊轉碼功能：修改 Program.cs

    • 前

      builder.Services.AddGrpc();

    • 後

      builder.Services.AddGrpc().AddJsonTranscoding();

  3. 新增 google/api/http.proto 與 google/api/annotations.proto

    引用額外的資料結構，以預設專案的例子可以在 Protos 資料下新增 google/api 並放入以下兩個檔案 (檔案位置會影響實際引用的設定，另個做法是與 .proj 放在同一層，引用填 .proj 的相對位置即可)

    • http.proto

      展開摺疊區塊

      // Copyright 2019 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;
}

    • annotations.proto

      展開摺疊區塊

      // 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 "Protos/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;
}

  4. 透過 HTTP binding 與 route 來標注 gRPC service

    修改範例中的 greet.proto 檔案：將原本使用 get 方法並透過 url parameter 傳遞參數改為 post 與 json

    • 前

      syntax = "proto3";
//以實際放的位置為主
import "Protos/google/api/annotations.proto";
option csharp_namespace = "NET7GrpcService";
        
package greet;
        
// The greeting service definition.
service Greeter {
  // Sends a greeting
  rpc SayHello (HelloRequest) returns (HelloReply){
      option (google.api.http) = {
        get: "/v1/greeter/{name}"
      };   
  }
}
        
// The request message containing the user's name.
message HelloRequest {
  string name = 1;
}
        
// The response message containing the greetings.
message HelloReply {
  string message = 1;
}

    • 後

      syntax = "proto3";
//以實際放的位置為主
import "Protos/google/api/annotations.proto";
option csharp_namespace = "NET7GrpcService";
        
package greet;
        
// The greeting service definition.
service Greeter {
  // Sends a greeting
  rpc SayHello (HelloRequest) returns (HelloReply){
      option (google.api.http) = {
        post: "/Greeter/SayHello",
        body: "*"
      };   
  }
}
        
// The request message containing the user's name.
message HelloRequest {
  string name = 1;
}
        
// The response message containing the greetings.
message HelloReply {
  string message = 1;
}

  5. (非必要，可在 macOS 上的啟用 insecure grpc) 設定 gRPC 與 rest api 走不同 port

    修改 appsettings.json

    • 前

      {
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "AllowedHosts": "*",
  "Kestrel": {
    "EndpointDefaults": {
      "Protocols": "Http2"
    }
  }
}

    • 後

      {
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "AllowedHosts": "*",
  "Kestrel": {
    "Endpoints": {
      "Https": {
        "Url": "https://*:7019",
        "Protocols": "Http1"
      },
      "GrpcInsecure" : {
        "Url": "http://*:5187",
        "Protocols": "Http2"
      }
    }
  }
}

  6. 實際效果

    兩者 port 不同，是因為 macOS 的源故

    • gRPC

      1grpc

    • rest api

      2rest

心得

這個調整純屬個人的喜好問題： gRPC 的 request body，rest 透過 POST 使用 json 感覺使用體驗比較一致，不過單就以範例這樣簡單的情境功能是完全相同的，只是如果 request 內容是個大型複雜型別的物件時，我個人相信 POST 是比較常見的做法

完整程式碼：yowko/grpc-aspdotnetcore7-json-post

參考資訊

  1. .NET 7 的新功能
  2. ASP.NET Core 7.0 的新功能
  3. ASP.NET Core gRPC 應用程式中的 gRPC JSON 轉碼
  4. gRPC JSON 轉碼與 Swagger/OpenAPI
  5. Build High Performance Services using gRPC and .NET7
  6. 針對 .NET Core 上的 gRPC 進行疑難排解
  7. yowko/grpc-aspdotnetcore7-json-post
  8. ASP.NET Core gRPC 的 Secure 與 Insecure 不同做法
  9. gRPC 在 ASP.NET Core 7 的 JSON 轉碼功能
  10. gRPC 在 ASP.NET Core 7 的 JSON 轉碼功能 (macOS)