source/memory: detect presence of NVDIMM devices

Add a new (binary) label indicating the presence of non-volatile DIMM
devices:
  feature.node.kubernetes.io/memory-nv.present

README.md

@@ -260,9 +260,10 @@ possible security implications.
 
 ### Memory Features
 
-| Feature name   | Description                                                                         |
+| Feature | Attribute | Description                                            |
-| :------------: | :---------------------------------------------------------------------------------: |
+| ------- | --------- | ------------------------------------------------------ |
-| numa           | Multiple memory nodes i.e. NUMA architecture detected
+| numa    | <br>      | Multiple memory nodes i.e. NUMA architecture detected
+| nv      | present   | NVDIMM device(s) are present
 
 ### Network Features
 

source/memory/memory.go

@@ -19,6 +19,7 @@ package memory
 import (
 	"io/ioutil"
 	"log"
+	"os"
 	"strings"
 
 	"sigs.k8s.io/node-feature-discovery/source"
@@ -42,6 +43,14 @@ func (s Source) Discover() (source.Features, error) {
 		features["numa"] = true
 	}
 
+	// Detect NVDIMM
+	nv, err := hasNvdimm()
+	if err != nil {
+		log.Printf("ERROR: failed to detect presence of NVDIMM: %s", err)
+	} else if nv {
+		features["nv.present"] = true
+	}
+
 	return features, nil
 }
 
@@ -64,3 +73,16 @@ func isNuma() (bool, error) {
 	}
 	return false, nil
 }
+
+// Detect presence of NVDIMM devices
+func hasNvdimm() (bool, error) {
+	devices, err := ioutil.ReadDir("/sys/class/nd/")
+	if err == nil {
+		if len(devices) > 0 {
+			return true, nil
+		}
+	} else if !os.IsNotExist(err) {
+		return false, err
+	}
+	return false, nil
+}