重试：仅幂等请求（GET）重试，最多 2 次，退避间隔 100ms
文章目录
-
- 什么是幂等性？
- 为什么只重试幂等请求？
-
- [1. **避免重复副作用**](#1. 避免重复副作用)
- [2. **HTTP方法的幂等性分类**](#2. HTTP方法的幂等性分类)
- [3. **实际风险示例**](#3. 实际风险示例)
- [4. **安全重试机制**](#4. 安全重试机制)
仅幂等请求重试的原因主要基于 幂等性的定义 和 避免数据一致性问题 ：
什么是幂等性？
幂等性（Idempotence）是指：一个操作执行一次和执行多次，产生的副作用（对系统状态的改变）完全相同。
为什么只重试幂等请求？
1. 避免重复副作用
-
幂等请求（如GET）：重试不会改变系统状态
- 例如：查询余额，无论查询多少次，账户余额都不会变
-
非幂等请求（如POST）：重试会产生重复副作用
- 例如：创建订单，每次POST都可能创建新订单
- 支付接口，重复支付会导致多次扣钱
2. HTTP方法的幂等性分类
| 方法 | 是否幂等 | 说明 |
|---|---|---|
| GET | ✅ 幂等 | 只读操作，不会改变服务器状态 |
| PUT | ✅ 幂等 | 多次更新相同数据，结果相同 |
| DELETE | ✅ 幂等 | 多次删除，结果相同 |
| POST | ❌ 非幂等 | 每次都可能创建新资源 |
| PATCH | ❌ 非幂等 | 部分更新，可能产生不同效果 |
3. 实际风险示例
如果对非幂等请求重试：
- 🚫 支付场景：网络超时后重试，用户被扣款两次
- 🚫 订单场景：用户点击提交后重试，创建多个相同订单
- 🚫 消息发送：重试导致重复发送消息
4. 安全重试机制
仅对幂等请求重试的好处：
- ✅ 安全：重试不会造成数据混乱
- ✅ 可靠：网络波动时能自动恢复
- ✅ 简化设计：服务端无需处理重复请求的去重逻辑
因此，重试策略限制为仅幂等请求（主要是GET），是为了在保证可用性的同时，避免因重试导致的数据不一致问题。
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