Support path stripping

This patch adds support for a 'strip=/path' option which will remove
/path from the front of the outgoing request path. For 'strip=/foo'
a request to '/foo/bar' will be matched on '/foo/bar' but forwarded
as '/bar'.

Fixes: #44, #124, #164

main.go

@@ -186,6 +186,7 @@ func watchBackend() {
 			continue
 		}
 		route.SetTable(t)
+		log.Printf("[INFO] Updated config to\n%s", t)
 
 		last = next
 	}

proxy/proxy.go

@@ -2,6 +2,7 @@ package proxy
 
 import (
 	"net/http"
+	"strings"
 	"time"
 
 	"github.com/eBay/fabio/config"
@@ -44,6 +45,14 @@ func (p *httpProxy) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// TODO(fs): The HasPrefix check seems redundant since the lookup function should
+	// TODO(fs): have found the target based on the prefix but there may be other
+	// TODO(fs): matchers which may have different rules. I'll keep this for
+	// TODO(fs): a defensive approach.
+	if t.StripPath != "" && strings.HasPrefix(r.URL.Path, t.StripPath) {
+		r.URL.Path = r.URL.Path[len(t.StripPath):]
+	}
+
 	upgrade, accept := r.Header.Get("Upgrade"), r.Header.Get("Accept")
 
 	var h http.Handler

proxy/proxy_integration_test.go

@@ -51,6 +51,32 @@ func TestProxyNoRouteStaus(t *testing.T) {
 	}
 }
 
+func TestProxyStripsPath(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.RequestURI != "/bar" {
+			w.WriteHeader(404)
+			return
+		}
+		w.Write([]byte("OK"))
+	}))
+	parseRoutes("route add mock /foo/bar " + server.URL + ` opts "strip=/foo"`)
+
+	tr := http.DefaultTransport
+	cfg := config.Proxy{}
+	proxy := NewHTTPProxy(tr, cfg)
+
+	req := testReq("/foo/bar")
+	rec := httptest.NewRecorder()
+	proxy.ServeHTTP(rec, req)
+
+	if got, want := rec.Code, http.StatusOK; got != want {
+		t.Fatalf("got status %d want %d", got, want)
+	}
+	if got, want := rec.Body.String(), "OK"; got != want {
+		t.Fatalf("got body %q want %q", got, want)
+	}
+}
+
 func TestProxyGzipHandler(t *testing.T) {
 	tests := []struct {
 		desc            string

route/route.go

@@ -59,9 +59,19 @@ func (r *Route) addTarget(service string, targetURL *url.URL, fixedWeight float6
 		log.Printf("[ERROR] Invalid metrics name: %s", err)
 		name = "unknown"
 	}
-	timer := ServiceRegistry.GetTimer(name)
 
-	t := &Target{Service: service, Tags: tags, URL: targetURL, FixedWeight: fixedWeight, Timer: timer, timerName: name}
+	t := &Target{
+		Service:     service,
+		Tags:        tags,
+		URL:         targetURL,
+		FixedWeight: fixedWeight,
+		Timer:       ServiceRegistry.GetTimer(name),
+		timerName:   name,
+	}
+	if r.Opts != nil {
+		t.StripPath = r.Opts["strip"]
+	}
+
 	r.Targets = append(r.Targets, t)
 	r.weighTargets()
 }

route/table.go

@@ -51,7 +51,6 @@ func SetTable(t Table) {
 	table.Store(t)
 	syncRegistry(t)
 	mu.Unlock()
-	log.Printf("[INFO] Updated config to\n%s", t)
 }
 
 // syncRegistry unregisters all inactive timers.

route/target.go

@@ -13,6 +13,10 @@ type Target struct {
 	// Tags are the list of tags for this target
 	Tags []string
 
+	// StripPath will be removed from the front of the outgoing
+	// request path
+	StripPath string
+
 	// URL is the endpoint the service instance listens on
 	URL *url.URL