Kratos Proto API

<objective> Create protobuf service definitions that generate both gRPC and HTTP/​JSON APIs with validation rules and OpenAPI specs for go-kratos microservices. </​objective>

<quick_start> Create proto file in api/​{service}/​v1/​{entity}.proto:

syntax = "proto3";

package {service}.v1;

import "google/​api/​annotations.proto";
import "validate/​validate.proto";

service {Entity}Service {
  rpc Create{Entity}(Create{Entity}Request) returns (Create{Entity}Response) {
    option (google.api.http) = {
      post: "/​v1/​{entities}"
      body: "*"
    };
  }
}

message Create{Entity}Request {
  string name = 1 [(validate.rules).string = {min_len: 1, max_len: 255}];
}

message Create{Entity}Response {
  {Entity} {entity} = 1;
}

message {Entity} {
  uint64 id = 1;
  string name = 2;
}

</​quick_start>

<service_patterns>

Service Definition

service {Entity}Service {
  // Create
  rpc Create{Entity}(Create{Entity}Request) returns (Create{Entity}Response) {
    option (google.api.http) = {
      post: "/​v1/​{entities}"
      body: "*"
    };
  }

  // Get
  rpc Get{Entity}(Get{Entity}Request) returns (Get{Entity}Response) {
    option (google.api.http) = {
      get: "/​v1/​{entities}/​{id}"
    };
  }

  // Update
  rpc Update{Entity}(Update{Entity}Request) returns (Update{Entity}Response) {
    option (google.api.http) = {
      put: "/​v1/​{entities}/​{id}"
      body: "*"
    };
  }

  // Delete
  rpc Delete{Entity}(Delete{Entity}Request) returns (Delete{Entity}Response) {
    option (google.api.http) = {
      delete: "/​v1/​{entities}/​{id}"
    };
  }

  // List
  rpc List{Entities}(List{Entities}Request) returns (List{Entities}Response) {
    option (google.api.http) = {
      get: "/​v1/​{entities}"
    };
  }
}

</​service_patterns>

<message_patterns>

Message Patterns

Create Request:

message Create{Entity}Request {
  string name = 1 [(validate.rules).string = {min_len: 1, max_len: 255}];
  uint64 project_id = 2 [(validate.rules).uint64 = {gt: 0}];
}

Update Request:

message Update{Entity}Request {
  uint64 id = 1 [(validate.rules).uint64 = {gt: 0}];
  string name = 2 [(validate.rules).string = {min_len: 1, max_len: 255}];
}

Get Request:

message Get{Entity}Request {
  uint64 id = 1 [(validate.rules).uint64 = {gt: 0}];
}

List Request:

message List{Entities}Request {
  uint64 offset = 1;
  uint64 limit = 2 [(validate.rules).uint64 = {gte: 1, lte: 100}];
}

List Response with Pagination:

message List{Entities}Response {
  repeated {Entity} {entities} = 1;
  PaginationMeta meta = 2;
}

message PaginationMeta {
  uint64 total = 1;
  uint64 offset = 2;
  uint64 limit = 3;
}

</​message_patterns>

<validation_rules>

Validation Rules

Strings:

string name = 1 [(validate.rules).string = {min_len: 1, max_len: 255}];
string email = 2 [(validate.rules).string = {email: true}];
string uuid = 3 [(validate.rules).string = {uuid: true}];
string status = 4 [(validate.rules).string = {in: ["active", "inactive"]}];

Numbers:

uint64 id = 1 [(validate.rules).uint64 = {gt: 0}];
uint32 count = 2 [(validate.rules).uint32 = {gte: 0, lte: 1000}];

Optional Fields: Omit validation or use ignore_empty: true </​validation_rules>

<http_annotations>

HTTP Mapping

REST patterns:

• POST /​v1/​{entities} - Create
• GET /​v1/​{entities}/​{id} - Get
• PUT /​v1/​{entities}/​{id} - Update
• DELETE /​v1/​{entities}/​{id} - Delete
• GET /​v1/​{entities} - List

Path variables:

rpc Get{Entity}(Get{Entity}Request) returns (Get{Entity}Response) {
  option (google.api.http) = {
    get: "/​v1/​{entities}/​{id}"  // {id} matches field in request
  };
}

message Get{Entity}Request {
  uint64 id = 1;  // Extracted from URL path
}

Query parameters (for GET/​DELETE): All request fields not in path become query params

Request body (for POST/​PUT): Use body: "*" to send entire request as JSON body </​http_annotations>

<file_structure>

Proto File Organization

api/​{service}/​v1/
├── {entity}.proto         # Main entity definitions
├── common.proto          # Shared messages (PaginationMeta, etc.)
└── errors.proto          # Error definitions (optional)

Required imports:

import "google/​api/​annotations.proto";
import "validate/​validate.proto";
import "google/​protobuf/​timestamp.proto";  // If using timestamps

</​file_structure>

<generation_commands>

After Creating Proto

1. Format proto files:

   make contracts-format
   

2. Lint proto files:

   make contracts-lint
   

3. Generate code:

   make contracts-generate
   

4. Check for breaking changes:

   make contracts-breaking
   

</​generation_commands>

<success_criteria> Proto definitions are correct when:

• Service name matches entity ({{Entity}Service)
• HTTP annotations follow REST conventions
• Validation rules on all required fields
• Message names follow {Operation}{Entity}{Request|Response}
• Path variables match request fields
• Repeated fields use plural names
• Imports include google/​api/​annotations and validate
• File compiles with make contracts-generate
• No breaking changes in make contracts-breaking </​success_criteria>