[Question] <The collection interval is not absolutely 30s>

### Question

阅读源码，发现指标时间是客户端调度时间，
目前场景会发现，每30s会产生1s的误差，以至于测试数据一直有周期性毛刺。下图：脚本每分钟两次写入，分别是3跟2值是5才是正确的

Start by tracing the client metric collection scheduler and the source of the metric timestamps described in the issue; the issue does not name a file or test. Reproduce the reported periodic one-second discrepancy with the described twice-per-minute writes, then establish expected interval and timestamp behavior before determining what a fix should verify.

Written by the indexing model from the issue text.