No notification is sent after the alert is triggered.

版本：v8.5.1
通知媒介：http 发送 post 到告警接口

现象：
1. 相同的告警规则，有时候会发送，有时候就不发

测试：
1. 创建新的告警规则：内存过高的指标
2. 降低阈值，触发告警，但接口没有收到任何数据
3. 手动在通知规则中选择此次告警点击测试通知，可以收到告警信息

如何解决这个问题？

Start by reproducing the intermittent notification failure with the described memory-threshold alert and HTTP POST notification, then compare it with the manual test notification that succeeds. Trace the alert-trigger path through notification delivery and verify whether the notification endpoint receives a request each time an alert fires. Done means triggered alerts consistently deliver the expected notification.

Written by the indexing model from the issue text.