API Design

tip

grpc 内部默认 4mb buffer

Google Cloud API 常见设计模式
- [start_xxx, end_xxx)
- map<string, string> labels
Microsoft/api-guidelines
https://cloud.google.com/apis/design/
https://opensource.zalando.com/restful-api-guidelines/
- zalando/zally
  - API linter
https://apistylebook.com/
- http://apistylebook.com/design/guidelines/
restcookbook/restcookbook
Atlassian REST API design guidelines version 1
- 集合名字 singular
adidas/api-guidelines
- https://adidas.gitbook.io/api-guidelines/
interagent/http-api-design
WhiteHouse/api-standards
https://postgrest.org/en/stable/api.html

设计场景

本地/内存
- 能够在内部持有引用，无需一次性加载或读写所有数据，支持逐步处理。
- 接口友好，直观简洁，方便开发者直接操作。
- 常见形式：handle, pointer, reference, object, entity
远程/网络
- 服务以 Request/Response 模式提供，保持 API 的简单性和可扩展性。
- 请求响应应保持单层关系：Service.Method(Request) -> Response。
- 尽量保持单个输入输出对象，避免多层嵌套。
- 信息设计相对浓缩：
  - 例如，使用字符串 "A > 1" 表示条件，而非复杂对象 {op: '>', field: 'A', value: 1}。
- 单个接口应功能丰富，覆盖特定用例。
- 需要考虑：序列化、包大小、状态、会话、幂等性、性能、错误处理、安全性。
- 常见形式：message, payload, data, object
封装
- 将复杂的远程或底层接口封装为类似本地接口，隐藏内部实现细节。
- 提供开发者友好的接口，便于快速上手。
- 提供便携的使用方式，降低集成成本。
- 常见形式：object, resource
系统/集成
- 尽量保持系统原貌，避免过度抽象导致系统功能受限。
- 不隐藏系统内部机制，便于开发者理解和排查问题。
- 按照系统本身的逻辑建模，提升兼容性和可维护性。
- 常见形式：syscall

分页和排序

Offset/Limit
- offset+limit
Cursor/Limit
- cursor+limit
- 时间: until, since
Zalando
- sort - +id,-name,-id
  - + asc, - desc
Google API
- order_by - field [asc|desc],...
MS API
- orderBy=name desc,hireDate

Meta GQL.json
{
  "data": [],
  "paging": {
    "cursors": {
      "after": "XYZ=",
      "before": "XYZ="
    },
    "previous": "https://?limit=25&before=XYZ=",
    "next": "https://?limit=25&after=XYZ="
  }
}

Twitter.json
{
  "ids": [123],
  "next_cursor": 123,
  "next_cursor_str": "123",
  "previous_cursor": -123,
  "previous_cursor_str": "-123"
}

{
  "items": [],
  "self": "http://?cursor=",
  "first": "",
  "prev": "",
  "next": "",
  "last": "",
  "query": {}
}

参考
- https://developers.facebook.com/docs/graph-api/results

过滤

tip

减少接口数量 - 提升开发效率
增加业务灵活性 - 业务变化接口不变

Filter

选择返回

tip

部分返回 - 性能
关联查询 - 客户端的开发体验
增加业务灵活性 - 业务变化接口不变
支持多端开发场景
GraphQL的出现解决了该问题

Google API
- fields=name,generation,size
- fields=items(id,metadata/key1)
Zalando
- fields - (name,friends(name))
  - 获取部分字段
  - 包含 name 和 friends 数组对象的 name
- embed - (items)
  - 包含关联属性
  - 包含额外内容
PostgREST
- GET /people?select=first_name,age HTTP/1.1
- GET /people?select=id,json_data->>blood_type,json_data->phones HTTP/1.1
  - JSON 数据选择
- GET /people?select=*,full_name HTTP/1.1
  - 额外字段

Zalando

查询参数
- q - 默认查询
- sort - 逗号分隔
  - +id,-name,-id
  - + asc, - desc
- fields - (name,friends(name))
  - 获取部分字段
- embed - (items)
  - 包含关联属性
- offset
- cursor
- limit

fields

<fields>            ::= [ <negation> ] <fields_struct>
<fields_struct>     ::= "(" <field_items> ")"
<field_items>       ::= <field> [ "," <field_items> ]
<field>             ::= <field_name> | <fields_substruct>
<fields_substruct>  ::= <field_name> <fields_struct>
<field_name>        ::= <dash_letter_digit> [ <field_name> ]
<dash_letter_digit> ::= <dash> | <letter> | <digit>
<dash>              ::= "-" | "_"
<letter>            ::= "A" | ... | "Z" | "a" | ... | "z"
<digit>             ::= "0" | ... | "9"
<negation>          ::= "!"

Google Cloud

fields=name,generation,size
fields=items(id,metadata/key1)
https://cloud.google.com/storage/docs/json_api#partial-response

gRPC API Design

接口面向资源
资源名字
- 资源必须包含资源名字
- 可以包含 <resource>_id
- 可以包含 uid
- ID 字段应该为字符串
- 例如
  - teams/first/members/wener
  - users/wener
- 完整资源名字
  - 服务名字/资源名字
  - //library.wener.me/publishers/123/books/456
    - 对于的类型 library.wener.me/Publisher, library.wener.me/Book
集合资源名字
- 复数、驼峰
- users/wener/events/hello-world
- 可以考虑支持跨集合
  - publishers/-/books/{book}
  - users/-/events?filter=
资源类型 - {Service Name}/{Type}
- ServiceName
- Type
GetResource(GetResourceRequest) returns (Resource)
- GetResourceRequest#name -- 资源名字 -> publishers/{publisher}/books/{book}
ListResources(ListResourceRequest) returns (ListResourceResponse)
- ListResourceRequest#
  - parent - 上级集合 -> publishers/*
  - page_size
  - page_token - 尽量前端不可逆
  - skip - 可选实现
  - order_by - field [asc|desc],...
  - filter - AIP-160
    - a AND b OR NOT c - OR 优先级高于 AND
    - NOT a = -a
    - =,!=,>,<,>=,<=
    - true,false,null
    - a.b = true
    - 包含/has a.b:10 - a 为集合，b 为集合元素字段
    - call(args...)
    - 字段名必须在左边
  - bool show_deleted - 软删除
  - unreachable
- ListResourceResponse
  - repeated Resource resources
  - next_page_token
  - 可选 int64 total_size
CreateResource(CreateResourceRequest) returns (Resource)
- CreateResourceRequest
  - parent
  - resource
  - resource_id 有些场景可以支持客户端自己指定
- 长时间运行操作返回 google.longrunning.Operation
UpdateResource(UpdateResourceRequest) returns (Resource)
- UpdateResourceRequest
  - resource
    - 通过 name 匹配
    - etag - 可指定 etga 进行比较更新，如果不匹配则失败
  - google.protobuf.FieldMask update_mask - 支持部分更新
  - bool allow_missing - 如果不存则创建
DeleteResource(DeleteResourceRequest) returns (google.protobuf.Empty)
DeleteResourceRequest
- name
- bool force - 强制级联删除
- etag - 如果匹配才删除
- bool allow_missing - 忽略不存在
PurgeResources(PurgeResourcesRequest) returns (google.longrunning.Operation)
- 批量删除
- PurgeResourcesRequest
  - parent
  - filter
  - force
- PurgeResourcesResponse
  - purge_count
  - purge_sample
UndeleteResource(UndeleteResourceRequest) returns (Resource)
- 支持软删除
- UndeleteResourceRequest
  - name
Batch
ImportResources(ImportResourcesRequest) returns (google.longrunning.Operation)
- ImportResourcesRequest
  - parent
ExportResources(ExportResourcesRequest) returns (google.longrunning.Operation)
- ExportResourcesRequest
  - filter
常见标准字段
- name
- parent
- uid
- display_name,title,given_name,faamily_ame
- create_time,update_time,delete_time
- expire_time - 软删除场景
- etag - checksum
常见请求字段
- request_id - UUID
- validate_only - Change validation
- google.protobuf.FieldMask
  - 不应该在请求包含 - 可以在 metadata 包含 - 例如头
  - 必须 optional
  - 支持 *
  - 现在推荐 view
- 例如 enum BookView {BOOK_VIEW_UNSPECIFIED=0;BASIC = 1;FULL = 2;}
单实例资源只有 Get 和 Update
https://google.aip.dev/
https://github.com/googleapis/googleapis/blob/master/google/api/
参考
- einride/aip-go
  - 包含了解析资源名字逻辑

Note

不要用 unsigned integer

不要用 optional - 除非表示特定含义 - 例如空为未投票、未评分

optional 会返回 zero value - 即便没有 set

entpb

一个资源一个服务
生成大量内容，但模式固定
entpb https://github.com/ent/contrib
#2446

syntax = "proto3";

service UserService {
  rpc Create ( CreateUserRequest ) returns ( User );
  rpc Get ( GetUserRequest ) returns ( User );
  rpc Update ( UpdateUserRequest ) returns ( User );
  rpc Delete ( DeleteUserRequest ) returns ( google.protobuf.Empty );
  rpc List ( ListUserRequest ) returns ( ListUserResponse );
  rpc BatchCreate ( BatchCreateUsersRequest ) returns ( BatchCreateUsersResponse );
}

message CreateUserRequest {
  User user = 1;
}

message GetUserRequest {
  int64 id = 1;
  View view = 2;

  enum View {
    VIEW_UNSPECIFIED = 0;
    BASIC = 1;
    WITH_EDGE_IDS = 2;
  }
}
message UpdateUserRequest {
  User user = 1;
}
message DeleteUserRequest {
  int64 id = 1;
}
message ListUserRequest {
  int32 page_size = 1;
  string page_token = 2;
  View view = 3;

  enum View {
    VIEW_UNSPECIFIED = 0;
    BASIC = 1;
    WITH_EDGE_IDS = 2;
  }
}
message ListUserResponse {
  repeated User user_list = 1;
  string next_page_token = 2;
}

message BatchCreateUsersRequest {
  repeated CreateUserRequest requests = 1;
}
message BatchCreateUsersResponse {
  repeated User users = 1;
}

https://github.com/ent/contrib/blob/1faab982b6648b7704a6cf41ff65d9cb7811a2be/entproto/internal/todo/ent/proto/entpb/entpb.proto

翻页参数

最终是需要 limit+offset
允许用户提供各种输入
- cursor 不在这个范围内

export function normalizePagination(page: {
  pageSize?: number;
  pageIndex?: number;
  pageNumber?: number;
  limit?: number;
  offset?: number;
}) {
  let { pageSize = 20, pageNumber = 1, pageIndex = pageNumber - 1, limit, offset } = page;
  return {
    limit: limit || pageSize,
    offset: offset ?? pageIndex * pageSize,
  };
}

游标翻页

cursor+limit
基本信息
- id/timestamp
- direction - 方向
  - 默认 > - 往后取
可以考虑额外的信息
- 例如排序字段

interface Cursor {
  id: string;
  direction: 'asc' | 'desc';
}

where id ${direction === 'asc' ? '>' : '<'} ${id}

pageInfo

relay 会返回 pageInfo 包含游标信息

export class RelayPageInfo {
  readonly startCursor?: RelayConnectionCursor | null;
  readonly endCursor?: RelayConnectionCursor | null;
  readonly hasPreviousPage!: boolean;
  readonly hasNextPage!: boolean;
}

Spring 的 Page 对象有类似信息
- https://docs.spring.io/spring-data/commons/docs/current/api/org/springframework/data/domain/PageImpl.html

export interface Page<T> {
  content: T[];
  // number of the current Slice
  number: number;
  // number of elements currently on this Slice.
  numberOfElements: number;

  pageable: Pageable;

  size: number;
  sort: Sort;

  totalElements: number;
  totalPages: number;

  hasContent(): boolean;
  hasNext(): boolean;
  hasPrevious(): boolean;
  isFirst(): boolean;
  isLast(): boolean;

  nextPageable(): Pageable;
  previousPageable(): Pageable;
}

interface Pageable {
  pageNumber: number;
  pageSize: number;
  offset: number;
  paged: boolean;
  sort: Sort;
  unpaged: boolean;
  paged: boolean;

  next(): Pageable;
  previousOrFirst(): Pageable;
  first(): Pageable;
}

interface Sort {
  sorted: boolean;
  unsorted: boolean;
  empty: boolean;

  orders: Order[];
}

interface Order {
  direction: 'ASC' | 'DESC';
  property: string;
  ignoreCase: boolean;
  nullHandling: 'NATIVE' | 'NULLS_FIRST' | 'NULLS_LAST';
  ascending: boolean;
  descending: boolean;
}

Django Rest Framework (DRF)
https://www.django-rest-framework.org/api-guide/pagination/

{
  "count": 1023,
  "next": "https://api.example.org/accounts/?limit=100&offset=500",
  "previous": "https://api.example.org/accounts/?limit=100&offset=300",
  "results": []
}

Prisma

const result = await prisma.user.findMany({
  take: 10,
  skip: 10,
});

Larval

{
  "total": 200,
  "per_page": 15,
  "current_page": 1,
  "last_page": 14,
  "next_page_url": "...",
  "prev_page_url": null,
  "from": 1,
  "to": 15,
  "data": []
}

Naming

PaginationResponse
PaginatedResponse
PaginationInfo

Grouping and Aggregation

大多需要分析场景的时候又会回到使用 DSL/SQL
参考

GET /my-index-000001/_search

{
  "size": 0,
  "aggs": {
    "my-agg-name": {
      "terms": {
        "field": "my-field"
      },
      "meta": {
        "my-metadata-field": "foo"
      }
    }
  }
}

{
  "aggregations": {
    "my-agg-name": {
      "meta": {
        "my-metadata-field": "foo"
      },
      "doc_count_error_upper_bound": 0,
      "sum_other_doc_count": 0,
      "buckets": [
        {
          "key": "foo",
          "doc_count": 5,
          "my-sub-agg-name": {
            "value": 75.0
          }
        }
      ]
    }
  }
}

FAQ

Payload vs Input vs Data vs Object vs Output

Payload - 载荷
- GraphQL 里一般 mutation 返回都是 Payload
- 不具有 Resource/Entity 属性
- CreateUserPayload, UpdateUserPayload
Input - 输入
- 强调数据作为输入
- GraphQL 里有 Input 概念区分于 Object 概念
- 具有 Resource/Entity 属性
- UserCreateInput, UserUpdateInput
Data - 数据
- 通用 - Data -> Key & Value
- 类似 Dicionary, Record, DTO
- UserCreationData, UserUpdateData
Object - 对象
- 通常内存表示
- 可能支持方法 - Object -> Method & Fields
- UserCreationObject, UserUpdateObject
Output
- 输出
- 强调可序列化的数据
- 用于 IO/API 交互场景
- 区分内部的 Entity
- 类似 Object
- 例如: UserEntity, UserOutput, UserObject - 避免都叫 User

设计场景​

分页和排序​

过滤​

选择返回​

Zalando​

Google Cloud​

gRPC API Design​

entpb​

翻页参数​

游标翻页​

pageInfo​

Naming​

Grouping and Aggregation​

FAQ

Payload vs Input vs Data vs Object vs Output​

设计场景

分页和排序

过滤

选择返回

Zalando

Google Cloud

gRPC API Design

entpb

翻页参数

游标翻页

pageInfo

Naming

Grouping and Aggregation

Payload vs Input vs Data vs Object vs Output