Make volumes-per-node limit configurable [CON-10973] (#575)

This is to support a future DO block storage volume limit increase.

Adjusting the limit in the driver is to allow the Kubernetes scheduler
to work correctly mostly. Specifically, it won't have an influence on
what the DO storage backend permits. The two need to be synchronized.

CHANGELOG.md

@@ -1,5 +1,8 @@
 ## unreleased
 
+* Make volumes-per-node limit configurable
+  [[GH-575]](https://github.com/digitalocean/csi-digitalocean/pull/575)
+
 ## v4.10.0 - 2024.06.05
 
 * Handle new max-volumes-per-node error message

cmd/do-csi-plugin/main.go

@@ -40,6 +40,7 @@ func main() {
 		defaultVolumesPageSize = flag.Uint("default-volumes-page-size", 0, "The default page size used when paging through volumes results (default: do not specify and let the DO API choose)")
 		doAPIRateLimitQPS      = flag.Float64("do-api-rate-limit", 0, "Impose QPS rate limit on DigitalOcean API usage (default: do not rate limit)")
 		validateAttachment     = flag.Bool("validate-attachment", false, "Validate if the attachment has fully completed before formatting/mounting the device")
+		volumeLimit            = flag.Uint("volume-limit", 7, "Volumes per node limit to report; needs to match limit imposed by DO storage backend (honored by Node service only)")
 		version                = flag.Bool("version", false, "Print the version and exit.")
 	)
 	flag.Parse()
@@ -64,6 +65,7 @@ func main() {
 		DefaultVolumesPageSize: *defaultVolumesPageSize,
 		DOAPIRateLimitQPS:      *doAPIRateLimitQPS,
 		ValidateAttachment:     *validateAttachment,
+		VolumeLimit:            *volumeLimit,
 	})
 	if err != nil {
 		log.Fatalln(err)

driver/driver.go

@@ -42,6 +42,8 @@ const (
 	// DefaultDriverName defines the name that is used in Kubernetes and the CSI
 	// system for the canonical, official name of this plugin
 	DefaultDriverName = "dobs.csi.digitalocean.com"
+
+	defaultMaxVolumesPerNode = 7
 )
 
 var (
@@ -86,8 +88,9 @@ type Driver struct {
 
 	// ready defines whether the driver is ready to function. This value will
 	// be used by the `Identity` service via the `Probe()` method.
-	readyMu sync.Mutex // protects ready
-	ready   bool
+	readyMu     sync.Mutex // protects ready
+	ready       bool
+	volumeLimit uint
 }
 
 // NewDriverParams defines the parameters that can be passed to NewDriver.
@@ -102,6 +105,7 @@ type NewDriverParams struct {
 	DefaultVolumesPageSize uint
 	DOAPIRateLimitQPS      float64
 	ValidateAttachment     bool
+	VolumeLimit            uint
 }
 
 // NewDriver returns a CSI plugin that contains the necessary gRPC
@@ -167,6 +171,7 @@ func NewDriver(p NewDriverParams) (*Driver, error) {
 		endpoint:               p.Endpoint,
 		debugAddr:              p.DebugAddr,
 		defaultVolumesPageSize: p.DefaultVolumesPageSize,
+		volumeLimit:            p.VolumeLimit,
 
 		hostID:  func() string { return hostID },
 		region:  region,
@@ -236,7 +241,7 @@ func (d *Driver) Run(ctx context.Context) error {
 			d.log.WithFields(logrus.Fields{
 				"limit":       details.limit,
 				"num_volumes": details.numVolumes,
-			}).Warn("CSI plugin will not function correctly, please resolve volume limit")
+			}).Warn("CSI plugin may not function correctly, please resolve volume limit")
 		}
 
 		if d.debugAddr != "" {

driver/driver_test.go

@@ -311,7 +311,7 @@ func (f *fakeStorageActionsDriver) Attach(ctx context.Context, volumeID string,
 		return nil, resp, errors.New("droplet was not found")
 	}
 
-	if len(droplet.VolumeIDs) >= maxVolumesPerNode {
+	if len(droplet.VolumeIDs) >= defaultMaxVolumesPerNode {
 		resp.Response = &http.Response{
 			StatusCode: http.StatusUnprocessableEntity,
 		}