Multi-ServiceBindings for a single application

Better handle multiple ServiceBinding resources each targeting the same
application resource. Depending on the order ServiceBindings are applied
to the resource, the order of the resulting volumes, volume mounts and
environment variables could differ. This difference could create churn
on the API server for semantically equivalent resources. Now, we attempt
to sort the entries injected into these lists for the ServiceBindings.

Signed-off-by: Scott Andrews <andrewssc@vmware.com>

pkg/apis/servicebindinginternal/v1alpha2/servicebindingprojection_lifecycle.go

@@ -9,6 +9,7 @@ import (
 	"context"
 	"crypto/sha1"
 	"fmt"
+	"sort"
 	"strings"
 
 	corev1 "k8s.io/api/core/v1"
@@ -25,6 +26,7 @@ const (
 	ServiceBindingProjectionConditionApplicationAvailable = "ApplicationAvailable"
 
 	ServiceBindingRootEnv = "SERVICE_BINDING_ROOT"
+	bindingVolumePrefix   = "binding-"
 )
 
 var sbpCondSet = apis.NewLivingConditionSet(
@@ -76,7 +78,7 @@ func (b *ServiceBindingProjection) Do(ctx context.Context, ps *duckv1.WithPod) {
 	newVolumes := sets.NewString()
 	sb := b.Spec.Binding
 
-	bindingVolume := truncateAt63("binding-%x", sha1.Sum([]byte(sb.Name)))
+	bindingVolume := truncateAt63("%s%x", bindingVolumePrefix, sha1.Sum([]byte(sb.Name)))
 	if !existingVolumes.Has(bindingVolume) {
 		ps.Spec.Template.Spec.Volumes = append(ps.Spec.Template.Spec.Volumes, corev1.Volume{
 			Name: bindingVolume,
@@ -86,6 +88,16 @@ func (b *ServiceBindingProjection) Do(ctx context.Context, ps *duckv1.WithPod) {
 				},
 			},
 		})
+		sort.SliceStable(ps.Spec.Template.Spec.Volumes, func(i, j int) bool {
+			iname := ps.Spec.Template.Spec.Volumes[i].Name
+			jname := ps.Spec.Template.Spec.Volumes[j].Name
+			// only sort injected volumes
+			// TODO be explicit about our bindings vs things that look like it might be our binding
+			if !strings.HasPrefix(iname, bindingVolumePrefix) || !strings.HasPrefix(jname, bindingVolumePrefix) {
+				return false
+			}
+			return iname < jname
+		})
 		existingVolumes.Insert(bindingVolume)
 		newVolumes.Insert(bindingVolume)
 	}
@@ -136,19 +148,41 @@ func (b *ServiceBindingProjection) doContainer(ctx context.Context, ps *duckv1.W
 			MountPath: fmt.Sprintf("%s/%s", mountPath, b.Spec.Name),
 			ReadOnly:  true,
 		})
+		sort.SliceStable(c.VolumeMounts, func(i, j int) bool {
+			iname := c.VolumeMounts[i].Name
+			jname := c.VolumeMounts[j].Name
+			// only sort injected volume mounts
+			// TODO be explicit about our bindings vs things that look like it might be our binding
+			if !strings.HasPrefix(iname, bindingVolumePrefix) || !strings.HasPrefix(jname, bindingVolumePrefix) {
+				return false
+			}
+			return iname < jname
+		})
 	}
 
-	for _, e := range b.Spec.Env {
-		c.Env = append(c.Env, corev1.EnvVar{
-			Name: e.Name,
-			ValueFrom: &corev1.EnvVarSource{
-				SecretKeyRef: &corev1.SecretKeySelector{
-					LocalObjectReference: corev1.LocalObjectReference{
-						Name: secretName,
+	if len(b.Spec.Env) != 0 {
+		for _, e := range b.Spec.Env {
+			c.Env = append(c.Env, corev1.EnvVar{
+				Name: e.Name,
+				ValueFrom: &corev1.EnvVarSource{
+					SecretKeyRef: &corev1.SecretKeySelector{
+						LocalObjectReference: corev1.LocalObjectReference{
+							Name: secretName,
+						},
+						Key: e.Key,
 					},
-					Key: e.Key,
 				},
-			},
+			})
+		}
+		sort.SliceStable(c.Env, func(i, j int) bool {
+			iv := c.Env[i]
+			jv := c.Env[j]
+			// only sort injected env
+			// TODO be explicit about our bindings vs things that look like it might be our binding
+			if iv.ValueFrom == nil || iv.ValueFrom.SecretKeyRef == nil || jv.ValueFrom == nil || jv.ValueFrom.SecretKeyRef == nil {
+				return false
+			}
+			return iv.Name < jv.Name
 		})
 	}
 }