prometheus notes
label_join(sum?by?(namespace,?pod_name)?(container_memory_usage_bytes{job="kubelet",?pod_name!="",?image!=""}),?"pod",?"",?"pod_name")?

[Prometheus-PQL](http://www.itdecent.cn/p/9cac39b94e9d)
[Prometheus學(xué)習(xí)系列(二十一)之PromQL函數(shù)](http://www.itdecent.cn/p/f77047fd8dca)
[prometheus.(4).函數(shù)計算公式](https://www.cnblogs.com/orange-lsc/p/12825562.html#by)