# rpc 错误：code = Canceled，desc = 上下文已取消

- **ID:** `go/grpc-canceled-by-client`
- **领域:** go
- **类别:** network_error
- **验证级别:** ai_generated
- **修复率:** 80%

## 根因

客户端在服务端完成前取消了 RPC（通过 context cancel、HTTP/2 RST_STREAM 或父上下文超时）。

## 版本兼容性

| 版本 | 状态 | 引入 | 弃用 |
|------|------|------|------|
| google.golang.org/grpc 1.48+ | active | — | — |

## 解决方案

1. **** (90% 成功率)
   ```
   Check ctx.Err() in the server handler and exit early:
select {
case <-ctx.Done():
    return nil, status.FromContextError(ctx.Err()).Err()
default:
}
// continue processing
   ```
2. **** (85% 成功率)
   ```
   Distinguish client cancel from server-side timeout by inspecting the parent context; treat codes.Canceled as INFO in logs and metrics.
   ```

## 无效尝试

- **** — If the caller intentionally canceled (e.g., user closed the page), retrying wastes resources. (80% 失败率)
- **** — Canceled is a normal client behavior; alerting creates noise. (85% 失败率)