Use encoded (raw) URL paths

Our kafka entities (e.g. consumer group names) contain unsafe symbols,
such as forward slash and colon. This change forces Burrow (httprouter)
to use encoded paths in URLs (Burrow plugin for Telegraf has always used
PathEscape from "net/url" to form Burrow URLs). With raw path support,
we do not loose metrics for groups with unsafe symbols in name.

Original pull request to support raw path in httprouter:
julienschmidt/httprouter#209, waiting for merge
since 2017. Looks like httprouter was abandoned around 2019.

The author switched to their own fork:
gravitational/teleport#12109. Let's do the same.

core/internal/httpserver/coordinator.go

@@ -57,6 +57,7 @@ type Coordinator struct {
 func (hc *Coordinator) Configure() {
 	hc.Log.Info("configuring")
 	hc.router = httprouter.New()
+	hc.router.UseRawPath = true
 
 	// If no HTTP server configured, add a default HTTP server that listens on a random port
 	servers := viper.GetStringMap("httpserver")

go.mod

@@ -68,3 +68,5 @@ require (
 	gopkg.in/ini.v1 v1.67.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
+
+replace github.com/julienschmidt/httprouter => github.com/gravitational/httprouter v1.3.1-0.20220408074523-c876c5e705a5

go.sum

@@ -31,6 +31,8 @@ github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
 github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/gorilla/securecookie v1.1.1/go.mod h1:ra0sb63/xPlUeL+yeDciTfxMRAA+MP+HVt/4epWDjd4=
 github.com/gorilla/sessions v1.2.1/go.mod h1:dk2InVEVJ0sfLlnXv9EAgkf6ecYs/i80K/zI+bUmuGM=
+github.com/gravitational/httprouter v1.3.1-0.20220408074523-c876c5e705a5 h1:qg8FcGwRACSHortU1UxCSo9nF0t34rPWjk9Nef3j2Ic=
+github.com/gravitational/httprouter v1.3.1-0.20220408074523-c876c5e705a5/go.mod h1:JR6WtHb+2LUe8TCKY3cZOxFyyO8IZAc4RVcycCCAKdM=
 github.com/hashicorp/errwrap v1.0.0/go.mod h1:YH+1FKiLXxHSkmPseP+kNlulaMuP3n2brvKWEqk/Jc4=
 github.com/hashicorp/errwrap v1.1.0 h1:OxrOeh75EUXMY8TBjag2fzXGZ40LB6IKw45YeGUDY2I=
 github.com/hashicorp/errwrap v1.1.0/go.mod h1:YH+1FKiLXxHSkmPseP+kNlulaMuP3n2brvKWEqk/Jc4=
@@ -53,8 +55,6 @@ github.com/jcmturner/gokrb5/v8 v8.4.4 h1:x1Sv4HaTpepFkXbt2IkL29DXRf8sOfZXo8eRKh6
 github.com/jcmturner/gokrb5/v8 v8.4.4/go.mod h1:1btQEpgT6k+unzCwX1KdWMEwPPkkgBtP+F6aCACiMrs=
 github.com/jcmturner/rpc/v2 v2.0.3 h1:7FXXj8Ti1IaVFpSAziCZWNzbNuZmnvw/i6CqLNdWfZY=
 github.com/jcmturner/rpc/v2 v2.0.3/go.mod h1:VUJYCIDm3PVOEHw8sgt091/20OJjskO/YJki3ELg/Hc=
-github.com/julienschmidt/httprouter v1.3.0 h1:U0609e9tgbseu3rBINet9P48AI/D3oJs4dN7jwJOQ1U=
-github.com/julienschmidt/httprouter v1.3.0/go.mod h1:JR6WtHb+2LUe8TCKY3cZOxFyyO8IZAc4RVcycCCAKdM=
 github.com/karrick/goswarm v1.10.0 h1:hGUt7r6O3bR02whvkW/E4rU6Ei7MekGGlTD5zqAYSHo=
 github.com/karrick/goswarm v1.10.0/go.mod h1:wqange6Y/RHXs23gBc4nRXPent8RaiFyfl2+otwXj8U=
 github.com/klauspost/compress v1.17.8 h1:YcnTYrq7MikUT7k0Yb5eceMmALQPYBW/Xltxn0NAMnU=