modifier: adding modifier tag concept

proxy/proxy.go

@@ -2,6 +2,7 @@ package proxy
 
 import (
 	"net/http"
+	"strings"
 	"time"
 
 	"github.com/eBay/fabio/config"
@@ -52,6 +53,16 @@ func (p *Proxy) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		h = newHTTPProxy(t.URL, p.tr)
 	}
 
+	// strip the prefix, if the target was tagged properly
+	if t.StripPrefix {
+		pieces := strings.SplitN(r.URL.Path, "/", 3)
+		if len(pieces) == 3 {
+			r.URL.Path = pieces[2]
+		} else {
+			r.URL.Path = "/"
+		}
+	}
+
 	start := time.Now()
 	h.ServeHTTP(w, r)
 	p.requests.UpdateSince(start)

route/route.go

@@ -3,6 +3,7 @@ package route
 import (
 	"fmt"
 	"net/url"
+	"regexp"
 	"sort"
 	"strings"
 
@@ -11,6 +12,8 @@ import (
 	gometrics "github.com/rcrowley/go-metrics"
 )
 
+var StripPrefixRegex *regexp.Regexp = regexp.MustCompile("modifier-/strip-prefix")
+
 // Route maps a path prefix to one or more target URLs.
 // routes can have a share value which describes the
 // amount of traffic this route should get. You can specify
@@ -51,7 +54,24 @@ func (r *Route) addTarget(service string, targetURL *url.URL, fixedWeight float6
 	name := metrics.TargetName(service, r.Host, r.Path, targetURL)
 	timer := gometrics.GetOrRegisterTimer(name, metrics.ServiceRegistry)
 
-	t := &Target{Service: service, Tags: tags, URL: targetURL, FixedWeight: fixedWeight, Timer: timer, timerName: name}
+	stripPrefix := false
+	// by passing a tag of `url-prefix-host/modifier#strip-prefix you can
+	// drop whatever prefix the service is namespaced by
+	for _, tag := range tags {
+		if StripPrefixRegex.MatchString(tag) {
+			stripPrefix = true
+		}
+	}
+
+	t := &Target{
+		Service:     service,
+		Tags:        tags,
+		URL:         targetURL,
+		StripPrefix: stripPrefix,
+		FixedWeight: fixedWeight,
+		Timer:       timer,
+		timerName:   name}
+
 	r.Targets = append(r.Targets, t)
 	r.weighTargets()
 }

route/target.go

@@ -16,6 +16,9 @@ type Target struct {
 	// URL is the endpoint the service instance listens on
 	URL *url.URL
 
+	// whether or not to strip the service prefix
+	StripPrefix bool
+
 	// FixedWeight is the weight assigned to this target.
 	// If the value is 0 the targets weight is dynamic.
 	FixedWeight float64