# UNAVAILABLE: 负载均衡器移除了流

- **ID:** `grpc/stream-removed-by-load-balancer`
- **领域:** grpc
- **类别:** network_error
- **验证级别:** ai_generated
- **修复率:** 78%

## 根因

gRPC负载均衡器（如gRPC-LB或Envoy）因后端健康检查失败或连接排空而移除了活跃流。

## 版本兼容性

| 版本 | 状态 | 引入 | 弃用 |
|------|------|------|------|
| gRPC v1.62.0 | active | — | — |
| Envoy v1.29.0 | active | — | — |
| gRPC-LB v1.8.0 | active | — | — |

## 解决方案

1. ```
   配置gRPC客户端重试策略和回退：设置环境变量'grpc.enable_retries=1'和'GRPC_RETRY_BUFFER_SIZE=32MB'；实现自定义重试拦截器，使用指数退避（如100ms、500ms、2s）。
   ```
2. ```
   调整负载均衡器健康检查间隔和超时：在Envoy中设置'health_check.interval: 5s'和'health_check.timeout: 2s'以减少误移除；对关键流设置'connection_drain_on_health_failure: false'。
   ```
3. ```
   实现客户端重连逻辑：使用gRPC的'Channelz'监控子通道状态，在'TRANSIENT_FAILURE'时重连（如'channel.watch_connectivity_state(grpc.ChannelConnectivity.TRANSIENT_FAILURE)'）。
   ```

## 无效尝试

- **** — Increasing client retry count without addressing load balancer health check fails because retries hit the same unhealthy backend. (85% 失败率)
- **** — Disabling TLS entirely reduces security and may mask underlying connection issues; the error persists if the load balancer still sees backend as unhealthy. (70% 失败率)
- **** — Restarting the client without adjusting load balancer configuration only temporarily reconnects; the error recurs on next health check failure. (90% 失败率)