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

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

## 根因

传给 RPC 的上下文在完成前被取消，可能由显式 cancel() 调用、父上下文取消，或客户端拦截器引起。服务器感知到取消并中止处理程序。

## 版本兼容性

| 版本 | 状态 | 引入 | 弃用 |
|------|------|------|------|
| 1.x | active | — | — |

## 解决方案

1. **** (88% 成功率)
   ```
   Derive a fresh context for retries and never reuse a canceled parent:

ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()
resp, err := client.Do(ctx, req)
if status.Code(err) == codes.Canceled {
    // parent was canceled; abort cleanly, don't retry with same ctx
}
   ```
2. **** (82% 成功率)
   ```
   Trace where the cancel is coming from — check for deferred cancel() firing too early or a request-scoped context tied to an HTTP handler that already returned:

// ensure cancel() is deferred AFTER the RPC completes, not before
ctx, cancel := context.WithTimeout(r.Context(), time.Second)
defer cancel()
resp, err := client.Do(ctx, req)
   ```

## 无效尝试

- **** — The context is already done; every call with it returns Canceled immediately without even reaching the server. (95% 失败率)
- **** — A canceled RPC returns a nil/zero response; proceeding as if it succeeded produces corrupt state downstream. (90% 失败率)