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**
- 2. **HTTP方法的幂等性分类**
- 3. **实际风险示例**
- 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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