In the absence of stats_tags to handle this pattern, when we pass
"ingress_upstream.$port" as the stat_prefix, Envoy splits up that prefix
and makes the port a part of the metric name.
For example:
- stat_prefix: ingress_upstream.8080
This leads to metric names like envoy_http_8080_no_route. Changing the
stat_prefix to ingress_upstream_80880 yields the expected metric names
such as envoy_http_no_route.
Note that we don't encode the destination's name/ns/dc in this
stat_prefix because for HTTP services ingress gateways use a single
filter chain. Only cluster metrics are available on a per-upstream
basis.
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