典型场景
典型场景
# 标签不一致时用 on 指定匹配键
sum by (instance) (rate(http_requests_total{code=~"5.."}[5m]))
/ on (instance) sum by (instance) (rate(http_requests_total[5m]))
# 多对一：把请求数附到实例信息上（group_left）
sum by (instance) (rate(http_requests_total[5m]))
* on (instance) group_left(node) count by (instance, node) (up == 1)向量匹配出错的典型表现：两个表达式单独都有数据，相除后为空；先检查两侧标签集差异。