Shorten DiskImage name if necessary

provisioner/cmd/provisioner/main.go

@@ -54,10 +54,24 @@ func NewGreenhostProvisioner() controller.Provisioner {
 	}
 }
 
+// Create a name for the cosmos DiskImage based on the name of the persistent
+// volume. We add a "ghost:" prefix, and shorten the name if necessary.
+func deriveDiskImageName(pvName string) string {
+	fullName := "ghost:" + pvName
+	// The maximum length of a disk name allowed by cosmos2 is 64.
+	if len(fullName) <= 64 {
+		return fullName
+	} else {
+                // Take the beginning and end of the string to attempt to
+		// preserve the most important information.
+		return fullName[0:31] + "*" + fullName[len(fullName)-32:len(fullName)]
+	}
+}
+
 // Provision creates a storage asset and returns a pv object representing it.
 func (p *GreenhostProvisioner) Provision(ctx context.Context, options controller.ProvisionOptions) (*v1.PersistentVolume, controller.ProvisioningState, error) {
 	pvName := options.PVC.ObjectMeta.Name
-	name := "kubernetes-ghost:" + pvName
+	name := deriveDiskImageName(pvName)
 	region := os.Getenv("GHOST_CLOUD_REGION")
 	backup := os.Getenv("GHOST_IMAGE_BACKUP")
 	backupBool := backup == "true"