driver: handle non existing volumes and nodes

According to the spec we should return a `NOT_FOUND` in various method.
We always assume the volume or node exist, however this might not the
case.

For example the user might delete the volume externally from the
UI or make a HTTP call to the DigitalOcean API to delete the volume.
Actions like this are outside the Kubernetes system, so the plugin needs
to handle these edge cases by signaling back that the resources don't
exist.

We return `NOT_FOUND` for any creation actions, such as creating a
volume, attaching a volume, formatting, etc.. Because we really need to
return an error as there is no way to recover from this

We don't return `NOT_FOUND` for any destroy actions, such as deleting,
detaching, unmounting, etc.. Because in all these cases it doesn't
matter if the volume doesn't exist. There is not much to do and assuming
it's "done" makes the overall system more stable

driver/controller.go

@@ -181,6 +181,22 @@ func (d *Driver) ControllerPublishVolume(ctx context.Context, req *csi.Controlle
 	})
 	ll.Info("controller publish volume called")
 
+	// check if volume exist before trying to attach it
+	_, resp, err := d.doClient.Storage.GetVolume(ctx, req.VolumeId)
+	if err != nil {
+		if resp != nil && resp.StatusCode == http.StatusNotFound {
+			return nil, status.Errorf(codes.NotFound, "volume %q not found", req.VolumeId)
+		}
+	}
+
+	// check if droplet exist before trying to attach the volume to the droplet
+	_, resp, err = d.doClient.Droplets.Get(ctx, dropletID)
+	if err != nil {
+		if resp != nil && resp.StatusCode == http.StatusNotFound {
+			return nil, status.Errorf(codes.NotFound, "droplet %q not found", dropletID)
+		}
+	}
+
 	action, resp, err := d.doClient.StorageActions.Attach(ctx, req.VolumeId, dropletID)
 	if err != nil {
 		// don't do anything if attached
@@ -224,6 +240,23 @@ func (d *Driver) ControllerUnpublishVolume(ctx context.Context, req *csi.Control
 	})
 	ll.Info("controller unpublish volume called")
 
+	// check if volume exist before trying to detach it
+	_, resp, err := d.doClient.Storage.GetVolume(ctx, req.VolumeId)
+	if err != nil {
+		if resp != nil && resp.StatusCode == http.StatusNotFound {
+			// assume it's detached
+			return &csi.ControllerUnpublishVolumeResponse{}, nil
+		}
+	}
+
+	// check if droplet exist before trying to detach the volume from the droplet
+	_, resp, err = d.doClient.Droplets.Get(ctx, dropletID)
+	if err != nil {
+		if resp != nil && resp.StatusCode == http.StatusNotFound {
+			return nil, status.Errorf(codes.NotFound, "droplet %q not found", dropletID)
+		}
+	}
+
 	action, resp, err := d.doClient.StorageActions.DetachByDropletID(ctx, req.VolumeId, dropletID)
 	if err != nil {
 		if (resp != nil && resp.StatusCode == http.StatusUnprocessableEntity) || strings.Contains(err.Error(), "Attachment not found") {
@@ -275,6 +308,14 @@ func (d *Driver) ValidateVolumeCapabilities(ctx context.Context, req *csi.Valida
 	})
 	ll.Info("validate volume capabilities called")
 
+	// check if volume exist before trying to validate it it
+	_, volResp, err := d.doClient.Storage.GetVolume(ctx, req.VolumeId)
+	if err != nil {
+		if volResp != nil && volResp.StatusCode == http.StatusNotFound {
+			return nil, status.Errorf(codes.NotFound, "volume %q not found", req.VolumeId)
+		}
+	}
+
 	hasSupport := func(mode csi.VolumeCapability_AccessMode_Mode) bool {
 		for _, m := range vcaps {
 			if mode == m.Mode {