Nginx ingress_controller pipeline can not parse domain socket

[leweafan]

Describe the enhancement:

Nginx ingress_controller pipeline supports only upstream format "IP:port" and doesn't support socket.
According to https://kubernetes.github.io/ingress-nginx/user-guide/nginx-configuration/log-format/ description of variable $upstream_addr:

the IP address and port (or the path to the domain socket) of the upstream server.

Nginx ingress_controller grok for variable nginx.ingress_controller.upstream_address_list:

UPSTREAM_ADDRESS_LIST (?:%{IP}(:%{NUMBER})?)(\"?,?\s*(?:%{IP}(:%{NUMBER})?))*

Describe a specific use case for the enhancement or feature:

$upstream_addr = "unix:/var/run/php5-fpm.sock"

[elasticmachine]

Pinging @elastic/integrations (Team:Integrations)

[leweafan]

Suppose new pattern should fix it

UPSTREAM_ADDRESS_LIST: (unix:%{NOTSPACE}|(?:%{IP}(:%{NUMBER})?)("?,?\s*(?:%{IP}(:%{NUMBER})?))*)