Support for configuring volume attachable limit on a node.

Author: avalluri

cmd/hostpathplugin/main.go

@@ -51,6 +51,7 @@ func main() {
 	flag.BoolVar(&cfg.EnableAttach, "enable-attach", false, "Enables RPC_PUBLISH_UNPUBLISH_VOLUME capability.")
 	flag.BoolVar(&cfg.EnableTopology, "enable-topology", true, "Enables PluginCapability_Service_VOLUME_ACCESSIBILITY_CONSTRAINTS capability.")
 	flag.BoolVar(&cfg.EnableVolumeExpansion, "node-expand-required", true, "Enables NodeServiceCapability_RPC_EXPAND_VOLUME capacity.")
+	flag.Int64Var(&cfg.AttachLimit, "attach-limit", 0, "Maximum number of attachable volumes on a node. Zero refers to no limit.")
 	showVersion := flag.Bool("version", false, "Show version.")
 	// The proxy-endpoint option is intended to used by the Kubernetes E2E test suite
 	// for proxying incoming calls to the embedded mock CSI driver.

pkg/hostpath/controllerserver.go

@@ -304,6 +304,11 @@ func (hp *hostPath) ControllerPublishVolume(ctx context.Context, req *csi.Contro
 		}, nil
 	}
 
+	// Check attach limit before publishing.
+	if hp.config.AttachLimit > 0 && hp.getAttachCount() >= hp.config.AttachLimit {
+		return nil, status.Errorf(codes.ResourceExhausted, "Cannot attach any more volumes to this node ('%s')", hp.config.NodeID)
+	}
+
 	vol.IsAttached = true
 	vol.ReadOnlyAttach = req.GetReadonly()
 	if err := hp.updateVolume(vol.VolID, vol); err != nil {

pkg/hostpath/hostpath.go

@@ -96,6 +96,7 @@ type Config struct {
 	NodeID                string
 	VendorVersion         string
 	MaxVolumesPerNode     int64
+	AttachLimit           int64
 	Capacity              Capacity
 	Ephemeral             bool
 	ShowVersion           bool
@@ -503,6 +504,16 @@ func (hp *hostPath) getSortedVolumeIDs() []string {
 	return ids
 }
 
+func (hp *hostPath) getAttachCount() int64 {
+	count := int64(0)
+	for _, vol := range hp.volumes {
+		if vol.IsAttached {
+			count++
+		}
+	}
+	return count
+}
+
 func filterVolumeName(targetPath string) string {
 	pathItems := strings.Split(targetPath, "kubernetes.io~csi/")
 	if len(pathItems) < 2 {

pkg/hostpath/nodeserver.go

@@ -313,6 +313,10 @@ func (hp *hostPath) NodeGetInfo(ctx context.Context, req *csi.NodeGetInfoRequest
 		}
 	}
 
+	if hp.config.AttachLimit > 0 {
+		resp.MaxVolumesPerNode = hp.config.AttachLimit
+	}
+
 	return resp, nil
 }