the server is currently unable to handle the request (get nodes.metrics.k8s.io)

在部署metrics server后，pod启动成功，但是使用kubectl top node命令时，显示报错：
Error from server (ServiceUnavailable): the server is currently unable to handle the request (get nodes.metrics.k8s.io)
多方查看后，发现在master节点上ping不同metrics server的podIP。两天的排错，才发现是使用calico网络bgp模式后，不同网段之间通信，pod不通
这里重新生成calico的ippool，使用calico网络的crosssubnet网络实现

# 1、备份当前的ippool
calicoctl get ippool -o yaml > pool_bak.yaml
# 2、修改pool_bak.yaml
#----在  natOutgoing: true后面添加一行，关闭该ippool
    disabled: true
# 3、应用使生效
calicoctl apply -f pool_bak.yaml
# 4、查看ippool
calicoctl get ippool -o wide
# ***如下显示
# --NAME                  CIDR           NAT    IPIPMODE      DISABLED   
# default-ipv4-ippool   10.66.0.0/16    true      Never        true      
# ****
# 5、删除旧的ippool
calicoctl delete pool default-ipv4-ippool
# 6、新建新的ippool
calicoctl create -f -<<EOF
apiVersion: projectcalico.org/v3
kind: IPPool
metadata:
  name: new-pool
spec:
  cidr: 10.67.0.0/16
  ipipMode: CrossSubnet
  natOutgoing: true
EOF
# 7、查看新的ippool
# NAME       CIDR           NAT    IPIPMODE      DISABLED   
# new-pool   10.66.0.0/16   true   CrossSubnet   false   

然后将metrics server等pods重新生成，就可以解决问题啦

BINGO
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BINGO