optimize: local cache global variable and reduce string object creation. and some code style.
optimize: local cache global variable and reduce string object creation.
and some code style.

caicloud/ingress,canhnt/ingress,caicloud/ingress,aledbf/ingress-nginx,kubernetes/ingress-nginx,kubernetes/ingress-nginx,canhnt/ingress,aledbf/ingress-nginx,kubernetes/ingress-nginx,aledbf/ingress-nginx,canhnt/ingress,canhnt/ingress,aledbf/ingress-nginx,kubernetes/ingress-nginx,caicloud/ingress,kubernetes/ingress-nginx,caicloud/ingress