proxy: always count route lookup failures

[AlexanderYastrebov]

Remove debug mode check for clarity and because
other metrics are updated without checking for debug mode.

[szuecs]

I didn't check but if you create 404 counts for unknown hosts then it's a DoS vector for memory usage.
If it's a single counter without host cardinality then it's fine.

[AlexanderYastrebov]

I didn't check but if you create 404 counts for unknown hosts then it's a DoS vector for memory usage.
If it's a single counter without host cardinality then it's fine.

Yes, this metric does not have client-controlled dimensions (like hostname):

$ bin/skipper -inline-routes='Host("foo.test") -> <shunt>' -metrics-flavour=prometheus
[APP]INFO[0000] Expose metrics in prometheus format
...

$ curl localhost:9090
Not Found
$ curl -s localhost:9911/metrics | grep skipper_route_error_total
# HELP skipper_route_error_total The total of route lookup errors.
# TYPE skipper_route_error_total counter
skipper_route_error_total 1

[MustafaSaber]

👍

[AlexanderYastrebov]

👍