We want to use tsweb to format Prometheus-style metrics from
our temporary golang.org/x/net/http2 fork, but we don't want http2
to depend on the tailscale.com module to use the concrete type
tailscale.com/metrics.LabelMap. Instead, let a expvar.Map be used
instead of it's annotated sufficiently in its name.
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
There's often some useful piece of information in there not already
repeated in the internal error.
Signed-off-by: David Crawshaw <crawshaw@tailscale.com>
The name's been bugging me for a long time.
I liked neither the overlap between tsweb.Handler and http.Handler,
nor the name "ServeHTTPErr" which sounds like it's an error being
returned, like it's an error handler and not sometimes a happy path.
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
