(avg by (instance) (rate(node_cpu_seconds_total{mode="iowait"}[5m])) * 100)
{instance="192.168.1.10:9103"}	0.0008771929824553427
{instance="192.168.1.11:9103"}	0.0008771929824553427
{instance="192.168.1.12:9103"}	0.004385964912280452

node_uname_info
node_uname_info{app="node-exporter",instance="192.168.1.10:9103",job="nodes",nodename="node10"}	1
node_uname_info{app="node-exporter",instance="192.168.1.11:9103",job="nodes",nodename="node11"}	1
node_uname_info{app="node-exporter",instance="192.168.1.12:9103",job="nodes",nodename="node12"} 1



(avg by (instance) (rate(node_cpu_seconds_total{mode="iowait"}[5m])) * 100) * on(instance) group_left (nodename) node_uname_info 

{instance="192.168.1.10:9103",nodename="node10"}	0.0008771929824553427
{instance="192.168.1.11:9103",nodename="node11"}	0.0008771929824553427
{instance="192.168.1.12:9103",nodename="node12"}	0.004385964912280452


on(instance) 


on(instance) 
左右两边根据 instance 进行匹配 ，值相等才会进行运算 

group_left (nodename) 
group_left() 的参数是右侧的标签名，将此标签值传递给左侧，覆盖左侧同名标签