Added nonrotational storage detection

This change adds feature source "storage".
Add label if any non-rotational block device is present in the node.
The label will be: nfd-storage-nonrotationaldisk=true

README.md

@@ -41,7 +41,7 @@ node-feature-discovery.
   -h --help                   Show this screen.
   --version                   Output version and exit.
   --sources=<sources>         Comma separated list of feature sources.
-                              [Default: cpuid,rdt,pstate,network]
+                              [Default: cpuid,rdt,pstate,network,storage]
   --no-publish                Do not publish discovered features to the
                               cluster-local Kubernetes API server.
   --label-whitelist=<pattern> Regular expression to filter label names to
@@ -58,6 +58,7 @@ The current set of feature sources are the following:
 - [Intel Resource Director Technology][intel-rdt]
 - [Intel P-State driver][intel-pstate]
 - Network
+- Storage
 
 ### Feature labels
 
@@ -79,7 +80,8 @@ the only label value published for features is the string `"true"`._
   "node.alpha.kubernetes-incubator.io/nfd-cpuid-<feature-name>": "true",
   "node.alpha.kubernetes-incubator.io/nfd-rdt-<feature-name>": "true",
   "node.alpha.kubernetes-incubator.io/nfd-pstate-<feature-name>": "true",
-  "node.alpha.kubernetes-incubator.io/nfd-network-<feature-name>": "true"
+  "node.alpha.kubernetes-incubator.io/nfd-network-<feature-name>": "true",
+  "node.alpha.kubernetes-incubator.io/nfd-storage-<feature-name>": "true"
 }
 ```
 
@@ -118,6 +120,12 @@ such as restricting discovered features with the --label-whitelist option._
 | :------------: | :---------------------------------------------------------------------------------: |
 | [SRIOV][sriov] | Single Root Input/Output Virtualization (SR-IOV) enabled Network Interface Card
 
+### Storage Features
+
+| Feature name       | Description                                                                         |
+| :--------------:   | :---------------------------------------------------------------------------------: |
+| nonrotationaldisk  | Non-rotational disk, like SSD, is present in the node
+
 ## Getting started
 ### System requirements
 

main.go

@@ -14,6 +14,7 @@ import (
 	"github.com/kubernetes-incubator/node-feature-discovery/source/network"
 	"github.com/kubernetes-incubator/node-feature-discovery/source/panic_fake"
 	"github.com/kubernetes-incubator/node-feature-discovery/source/pstate"
+	"github.com/kubernetes-incubator/node-feature-discovery/source/storage"
 	"github.com/kubernetes-incubator/node-feature-discovery/source/rdt"
 	api "k8s.io/api/core/v1"
 	meta_v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -108,7 +109,7 @@ func argsParse(argv []string) (noPublish bool, sourcesArg []string, whiteListArg
   -h --help                   Show this screen.
   --version                   Output version and exit.
   --sources=<sources>         Comma separated list of feature sources.
-                              [Default: cpuid,rdt,pstate,network]
+                              [Default: cpuid,rdt,pstate,network,storage]
   --no-publish                Do not publish discovered features to the
                               cluster-local Kubernetes API server.
   --label-whitelist=<pattern> Regular expression to filter label names to
@@ -144,6 +145,7 @@ func configureParameters(sourcesArg []string, whiteListArg string) (sources []so
 		rdt.Source{},
 		pstate.Source{},
 		network.Source{},
+		storage.Source{},
 		fake.Source{},
 		panic_fake.Source{},
 	}

main_test.go

@@ -132,7 +132,7 @@ func TestArgsParse(t *testing.T) {
 
 			Convey("noPublish is set and sourcesArg is set to the default value", func() {
 				So(noPublish, ShouldBeTrue)
-				So(sourcesArg, ShouldResemble, []string{"cpuid", "rdt", "pstate", "network"})
+				So(sourcesArg, ShouldResemble, []string{"cpuid", "rdt", "pstate", "network", "storage"})
 				So(len(whiteListArg), ShouldEqual, 0)
 			})
 		})
@@ -152,7 +152,7 @@ func TestArgsParse(t *testing.T) {
 
 			Convey("whiteListArg is set to appropriate value and sourcesArg is set to default value", func() {
 				So(noPublish, ShouldBeFalse)
-				So(sourcesArg, ShouldResemble, []string{"cpuid", "rdt", "pstate", "network"})
+				So(sourcesArg, ShouldResemble, []string{"cpuid", "rdt", "pstate", "network", "storage"})
 				So(whiteListArg, ShouldResemble, ".*rdt.*")
 			})
 		})

source/storage/storage.go

@@ -0,0 +1,51 @@
+/*
+Copyright 2018 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package storage
+
+import (
+	"fmt"
+	"io/ioutil"
+)
+
+// Source implements FeatureSource.
+type Source struct{}
+
+// Name returns an identifier string for this feature source.
+func (s Source) Name() string { return "storage" }
+
+// Discover returns feature names for storage: nonrotationaldisk if any SSD drive present.
+func (s Source) Discover() ([]string, error) {
+	features := []string{}
+
+	// Check if there is any non-rotational block devices attached to the node
+	blockdevices, err := ioutil.ReadDir("/sys/block/")
+	if err == nil {
+		for _, bdev := range blockdevices {
+			fname := "/sys/block/" + bdev.Name() + "/queue/rotational"
+			bytes, err := ioutil.ReadFile(fname)
+			if err != nil {
+				return nil, fmt.Errorf("can't read rotational status: %s", err.Error())
+			}
+			if bytes[0] == byte('0') {
+				// Non-rotational storage is present, add label.
+				features = append(features, "nonrotationaldisk")
+				break
+			}
+		}
+	}
+	return features, nil
+}