cache the authorisers rather than recreating them

pkg/env/core.go

@@ -37,7 +37,7 @@ type Core interface {
 	IsLocalDevelopmentMode() bool
 	IsCI() bool
 	NewMSITokenCredential() (azcore.TokenCredential, error)
-	NewMSIAuthorizer(...string) (autorest.Authorizer, error)
+	NewMSIAuthorizer(scope string) (autorest.Authorizer, error)
 	NewLiveConfigManager(context.Context) (liveconfig.Manager, error)
 	instancemetadata.InstanceMetadata
 
@@ -53,6 +53,8 @@ type core struct {
 
 	component    ServiceComponent
 	componentLog *logrus.Entry
+
+	msiAuthorizers map[string]autorest.Authorizer
 }
 
 func (c *core) IsLocalDevelopmentMode() bool {
@@ -109,6 +111,7 @@ func NewCore(ctx context.Context, log *logrus.Entry, component ServiceComponent)
 		isCI:                   isCI,
 		component:              component,
 		componentLog:           componentLog,
+		msiAuthorizers:         map[string]autorest.Authorizer{},
 	}, nil
 }
 
@@ -131,5 +134,6 @@ func NewCoreForCI(ctx context.Context, log *logrus.Entry) (Core, error) {
 	return &core{
 		InstanceMetadata:       im,
 		isLocalDevelopmentMode: isLocalDevelopmentMode,
+		msiAuthorizers:         map[string]autorest.Authorizer{},
 	}, nil
 }

pkg/env/msiauthorizer.go

@@ -50,10 +50,19 @@ func (c *core) NewMSITokenCredential() (azcore.TokenCredential, error) {
 	return azidentity.NewClientSecretCredential(tenantId, azureClientId, azureClientSecret, options)
 }
 
-func (c *core) NewMSIAuthorizer(scopes ...string) (autorest.Authorizer, error) {
+func (c *core) NewMSIAuthorizer(scope string) (autorest.Authorizer, error) {
+	// To prevent creating multiple authorisers with independent token
+	// refreshes, store them in a cache per-scope when created
+	auth, ok := c.msiAuthorizers[scope]
+	if ok {
+		return auth, nil
+	}
+
 	token, err := c.NewMSITokenCredential()
 	if err != nil {
 		return nil, err
 	}
-	return azidext.NewTokenCredentialAdapter(token, scopes), nil
+	auth = azidext.NewTokenCredentialAdapter(token, []string{scope})
+	c.msiAuthorizers[scope] = auth
+	return auth, nil
 }