Send Tekton installation namespace to EL

The EventListener did not have knowledge of which namespace Triggers was
installed in. Instead it always assumed it was `tekton-pipelines` leading to
the bug described in tektoncd#923.  This commit fixes this by having the Reconciler
send the installation namespace as a environment variable set on the
EventListener's pod.

NOTE: This fix is temporary and should not be necessary once tektoncd#869 is
implemented since then we will resolve the Interceptor's address using
information from its CRD.

Fixes tektoncd#923

Signed-off-by: Dibyo Mukherjee <dibyo@google.com>

pkg/interceptors/interceptors.go

@@ -24,10 +24,9 @@ import (
 	"io/ioutil"
 	"net/http"
 	"net/url"
+	"os"
 	"path"
 
-	"github.com/tektoncd/triggers/pkg/system"
-
 	"google.golang.org/grpc/codes"
 
 	triggersv1 "github.com/tektoncd/triggers/pkg/apis/triggers/v1alpha1"
@@ -188,7 +187,7 @@ func ResolveURL(i *triggersv1.TriggerInterceptor) *url.URL {
 	}
 	return &url.URL{
 		Scheme: "http",
-		Host:   fmt.Sprintf("%s.%s.svc", CoreInterceptorsHost, system.DefaultNamespace),
+		Host:   fmt.Sprintf("%s.%s.svc", CoreInterceptorsHost, os.Getenv("TEKTON_INSTALL_NAMESPACE")),
 		Path:   path,
 	}
 }

pkg/interceptors/interceptors_test.go

@@ -22,6 +22,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"net/url"
+	"os"
 	"strings"
 	"testing"
 
@@ -327,12 +328,27 @@ func TestResolvePath(t *testing.T) {
 		want: "http://tekton-triggers-core-interceptors.tekton-pipelines.svc",
 	}} {
 		t.Run(tc.want, func(t *testing.T) {
+			os.Setenv("TEKTON_INSTALL_NAMESPACE", "tekton-pipelines")
+			t.Cleanup(func() { os.Unsetenv("TEKTON_INSTALL_NAMESPACE") })
 			got := interceptors.ResolveURL(&tc.in)
 			if tc.want != got.String() {
 				t.Fatalf("ResolveURL() want: %s; got: %s", tc.want, got)
 			}
 		})
 	}
+
+	t.Run("different namespaces", func(t *testing.T) {
+		os.Setenv("TEKTON_INSTALL_NAMESPACE", "another-namespace")
+		t.Cleanup(func() {os.Unsetenv("TEKTON_INSTALL_NAMESPACE")})
+		in := &triggersv1.EventInterceptor{
+			Bitbucket: &triggersv1.BitbucketInterceptor{},
+		}
+		got := interceptors.ResolveURL(in)
+		want := "http://tekton-triggers-core-interceptors.another-namespace.svc/bitbucket"
+		if want != got.String() {
+			t.Fatalf("ResolveURL() want: %s; got: %s", want, got)
+		}
+	})
 }
 
 // testServer creates a httptest server with the passed in handler and returns a http.Client that

pkg/reconciler/v1alpha1/eventlistener/eventlistener.go

@@ -26,6 +26,7 @@ import (
 	"github.com/google/go-cmp/cmp/cmpopts"
 	"github.com/tektoncd/triggers/pkg/apis/triggers/v1alpha1"
 	listers "github.com/tektoncd/triggers/pkg/client/listers/triggers/v1alpha1"
+	"github.com/tektoncd/triggers/pkg/system"
 	"go.uber.org/zap"
 	"golang.org/x/xerrors"
 	appsv1 "k8s.io/api/apps/v1"
@@ -462,6 +463,9 @@ func getContainer(el *v1alpha1.EventListener, c Config) corev1.Container {
 				FieldPath: "metadata.namespace",
 			},
 		},
+	}, {
+		Name:  "TEKTON_INSTALL_NAMESPACE",
+		Value: system.GetNamespace(),
 	}}
 
 	certEnv := map[string]*corev1.EnvVarSource{}

pkg/reconciler/v1alpha1/eventlistener/eventlistener_test.go

@@ -248,6 +248,9 @@ func makeDeployment(ops ...func(d *appsv1.Deployment)) *appsv1.Deployment {
 									FieldPath: "metadata.namespace",
 								},
 							},
+						}, {
+							Name: "TEKTON_INSTALL_NAMESPACE",
+							Value: "tekton-pipelines",
 						}},
 					}},
 					Volumes: []corev1.Volume{{
@@ -333,6 +336,9 @@ var withTLSConfig = func(d *appsv1.Deployment) {
 					FieldPath: "metadata.namespace",
 				},
 			},
+		},{
+			Name: "TEKTON_INSTALL_NAMESPACE",
+			Value: "tekton-pipelines",
 		}, {
 			Name: "TLS_CERT",
 			ValueFrom: &corev1.EnvVarSource{