Add os release collector

Currently Node Exporter has a metric called `node_uname_info` which of
course exposes uname info. While this is nice, it does not help if you
are running different OSes which could have similar uname info.

Therefore parse `/etc/os-release` or `/usr/lib/os-release` and expose a
`node_os_info` metric which provide information regarding the OS
release/version of the node. Also expose the major.minor part of the OS
release version as `node_os_version`.

Since the os-release files will not change often, cache the parsed
content and only refresh the cache if the modification time changes.

This `os` collector will read files outside of `/proc` and `/sys`, but
the os-release file is widely used and the format is standardized:
https://www.freedesktop.org/software/systemd/man/os-release.html

Bug: https://github.com/prometheus/node_exporter/issues/1574
Signed-off-by: Benjamin Drung <benjamin.drung@ionos.com>

README.md

@@ -114,6 +114,7 @@ netstat | Exposes network statistics from `/proc/net/netstat`. This is the same
 nfs | Exposes NFS client statistics from `/proc/net/rpc/nfs`. This is the same information as `nfsstat -c`. | Linux
 nfsd | Exposes NFS kernel server statistics from `/proc/net/rpc/nfsd`. This is the same information as `nfsstat -s`. | Linux
 nvme | Exposes NVMe info from `/sys/class/nvme/` | Linux
+os | Expose OS release info from `/etc/os-release` or `/usr/lib/os-release` | _any_
 powersupplyclass | Exposes Power Supply statistics from `/sys/class/power_supply` | Linux
 pressure | Exposes pressure stall statistics from `/proc/pressure/`. | Linux (kernel 4.20+ and/or [CONFIG\_PSI](https://www.kernel.org/doc/html/latest/accounting/psi.html))
 rapl | Exposes various statistics from `/sys/class/powercap`. | Linux

collector/fixtures/e2e-64k-page-output.txt

@@ -2442,6 +2442,12 @@ node_nfsd_server_threads 8
 # HELP node_nvme_info Non-numeric data from /sys/class/nvme/<device>, value is always 1.
 # TYPE node_nvme_info gauge
 node_nvme_info{device="nvme0",firmware_revision="1B2QEXP7",model="Samsung SSD 970 PRO 512GB",serial="S680HF8N190894I",state="live"} 1
+# HELP node_os_info A metric with a constant '1' value labeled by build_id, id, id_like, image_id, image_version, name, pretty_name, variant, variant_id, version, version_codename, version_id.
+# TYPE node_os_info gauge
+node_os_info{build_id="",id="ubuntu",id_like="debian",image_id="",image_version="",name="Ubuntu",pretty_name="Ubuntu 20.04.2 LTS",variant="",variant_id="",version="20.04.2 LTS (Focal Fossa)",version_codename="focal",version_id="20.04"} 1
+# HELP node_os_version Metric containing the major.minor part of the OS version.
+# TYPE node_os_version gauge
+node_os_version{id="ubuntu",id_like="debian",name="Ubuntu"} 20.04
 # HELP node_power_supply_capacity capacity value of /sys/class/power_supply/<power_supply>.
 # TYPE node_power_supply_capacity gauge
 node_power_supply_capacity{power_supply="BAT0"} 81
@@ -2590,6 +2596,7 @@ node_scrape_collector_success{collector="netstat"} 1
 node_scrape_collector_success{collector="nfs"} 1
 node_scrape_collector_success{collector="nfsd"} 1
 node_scrape_collector_success{collector="nvme"} 1
+node_scrape_collector_success{collector="os"} 1
 node_scrape_collector_success{collector="powersupplyclass"} 1
 node_scrape_collector_success{collector="pressure"} 1
 node_scrape_collector_success{collector="processes"} 1

collector/fixtures/e2e-output.txt

@@ -2640,6 +2640,12 @@ node_nfsd_server_threads 8
 # HELP node_nvme_info Non-numeric data from /sys/class/nvme/<device>, value is always 1.
 # TYPE node_nvme_info gauge
 node_nvme_info{device="nvme0",firmware_revision="1B2QEXP7",model="Samsung SSD 970 PRO 512GB",serial="S680HF8N190894I",state="live"} 1
+# HELP node_os_info A metric with a constant '1' value labeled by build_id, id, id_like, image_id, image_version, name, pretty_name, variant, variant_id, version, version_codename, version_id.
+# TYPE node_os_info gauge
+node_os_info{build_id="",id="ubuntu",id_like="debian",image_id="",image_version="",name="Ubuntu",pretty_name="Ubuntu 20.04.2 LTS",variant="",variant_id="",version="20.04.2 LTS (Focal Fossa)",version_codename="focal",version_id="20.04"} 1
+# HELP node_os_version Metric containing the major.minor part of the OS version.
+# TYPE node_os_version gauge
+node_os_version{id="ubuntu",id_like="debian",name="Ubuntu"} 20.04
 # HELP node_power_supply_capacity capacity value of /sys/class/power_supply/<power_supply>.
 # TYPE node_power_supply_capacity gauge
 node_power_supply_capacity{power_supply="BAT0"} 81
@@ -2791,6 +2797,7 @@ node_scrape_collector_success{collector="netstat"} 1
 node_scrape_collector_success{collector="nfs"} 1
 node_scrape_collector_success{collector="nfsd"} 1
 node_scrape_collector_success{collector="nvme"} 1
+node_scrape_collector_success{collector="os"} 1
 node_scrape_collector_success{collector="powersupplyclass"} 1
 node_scrape_collector_success{collector="pressure"} 1
 node_scrape_collector_success{collector="processes"} 1

collector/fixtures/usr/lib/os-release

@@ -0,0 +1,12 @@
+NAME="Ubuntu"
+VERSION="20.04.2 LTS (Focal Fossa)"
+ID=ubuntu
+ID_LIKE=debian
+PRETTY_NAME="Ubuntu 20.04.2 LTS"
+VERSION_ID="20.04"
+HOME_URL="https://www.ubuntu.com/"
+SUPPORT_URL="https://help.ubuntu.com/"
+BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
+PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
+VERSION_CODENAME=focal
+UBUNTU_CODENAME=focal

collector/os_release.go

@@ -0,0 +1,178 @@
+// Copyright 2021 The Prometheus 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 collector
+
+import (
+	"errors"
+	"io"
+	"os"
+	"regexp"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/go-kit/log"
+	"github.com/go-kit/log/level"
+	envparse "github.com/hashicorp/go-envparse"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+const (
+	etcOSRelease    = "/etc/os-release"
+	usrLibOSRelease = "/usr/lib/os-release"
+)
+
+var (
+	versionRegex = regexp.MustCompile(`^[0-9]+\.?[0-9]*`)
+)
+
+type osRelease struct {
+	Name            string
+	ID              string
+	IDLike          string
+	PrettyName      string
+	Variant         string
+	VariantID       string
+	Version         string
+	VersionID       string
+	VersionCodename string
+	BuildID         string
+	ImageID         string
+	ImageVersion    string
+}
+
+type osReleaseCollector struct {
+	infoDesc           *prometheus.Desc
+	logger             log.Logger
+	os                 *osRelease
+	osFilename         string    // file name of cached release information
+	osMtime            time.Time // mtime of cached release file
+	osMutex            sync.Mutex
+	osReleaseFilenames []string // all os-release file names to check
+	version            float64
+	versionDesc        *prometheus.Desc
+}
+
+func init() {
+	registerCollector("os", defaultEnabled, NewOSCollector)
+}
+
+// NewOSCollector returns a new Collector exposing os-release information.
+func NewOSCollector(logger log.Logger) (Collector, error) {
+	return &osReleaseCollector{
+		logger: logger,
+		infoDesc: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, "os", "info"),
+			"A metric with a constant '1' value labeled by build_id, id, id_like, image_id, image_version, "+
+				"name, pretty_name, variant, variant_id, version, version_codename, version_id.",
+			[]string{"build_id", "id", "id_like", "image_id", "image_version", "name", "pretty_name",
+				"variant", "variant_id", "version", "version_codename", "version_id"}, nil,
+		),
+		osReleaseFilenames: []string{etcOSRelease, usrLibOSRelease},
+		versionDesc: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, "os", "version"),
+			"Metric containing the major.minor part of the OS version.",
+			[]string{"id", "id_like", "name"}, nil,
+		),
+	}, nil
+}
+
+func parseOSRelease(r io.Reader) (*osRelease, error) {
+	env, err := envparse.Parse(r)
+	return &osRelease{
+		Name:            env["NAME"],
+		ID:              env["ID"],
+		IDLike:          env["ID_LIKE"],
+		PrettyName:      env["PRETTY_NAME"],
+		Variant:         env["VARIANT"],
+		VariantID:       env["VARIANT_ID"],
+		Version:         env["VERSION"],
+		VersionID:       env["VERSION_ID"],
+		VersionCodename: env["VERSION_CODENAME"],
+		BuildID:         env["BUILD_ID"],
+		ImageID:         env["IMAGE_ID"],
+		ImageVersion:    env["IMAGE_VERSION"],
+	}, err
+}
+
+func (c *osReleaseCollector) UpdateStruct(path string) error {
+	releaseFile, err := os.Open(path)
+	if err != nil {
+		return err
+	}
+	defer releaseFile.Close()
+
+	stat, err := releaseFile.Stat()
+	if err != nil {
+		return err
+	}
+
+	t := stat.ModTime()
+	if path == c.osFilename && t == c.osMtime {
+		// osReleaseCollector struct is already up-to-date.
+		return nil
+	}
+
+	// Acquire a lock to update the osReleaseCollector struct.
+	c.osMutex.Lock()
+	defer c.osMutex.Unlock()
+
+	level.Debug(c.logger).Log("msg", "file modification time has changed",
+		"file", path, "old_value", c.osMtime, "new_value", t)
+	c.osFilename = path
+	c.osMtime = t
+
+	c.os, err = parseOSRelease(releaseFile)
+	if err != nil {
+		return err
+	}
+
+	majorMinor := versionRegex.FindString(c.os.VersionID)
+	if majorMinor != "" {
+		c.version, err = strconv.ParseFloat(majorMinor, 64)
+		if err != nil {
+			return err
+		}
+	} else {
+		c.version = 0
+	}
+	return nil
+}
+
+func (c *osReleaseCollector) Update(ch chan<- prometheus.Metric) error {
+	for i, path := range c.osReleaseFilenames {
+		err := c.UpdateStruct(*rootfsPath + path)
+		if err == nil {
+			break
+		}
+		if errors.Is(err, os.ErrNotExist) {
+			if i >= (len(c.osReleaseFilenames) - 1) {
+				level.Debug(c.logger).Log("msg", "no os-release file found", "files", strings.Join(c.osReleaseFilenames, ","))
+				return ErrNoData
+			}
+			continue
+		}
+		return err
+	}
+
+	ch <- prometheus.MustNewConstMetric(c.infoDesc, prometheus.GaugeValue, 1.0,
+		c.os.BuildID, c.os.ID, c.os.IDLike, c.os.ImageID, c.os.ImageVersion, c.os.Name, c.os.PrettyName,
+		c.os.Variant, c.os.VariantID, c.os.Version, c.os.VersionCodename, c.os.VersionID)
+	if c.version > 0 {
+		ch <- prometheus.MustNewConstMetric(c.versionDesc, prometheus.GaugeValue, c.version,
+			c.os.ID, c.os.IDLike, c.os.Name)
+	}
+	return nil
+}

collector/os_release_test.go

@@ -0,0 +1,105 @@
+// Copyright 2021 The Prometheus 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 collector
+
+import (
+	"os"
+	"reflect"
+	"strings"
+	"testing"
+
+	"github.com/go-kit/log"
+)
+
+const debianBullseye string = `PRETTY_NAME="Debian GNU/Linux 11 (bullseye)"
+NAME="Debian GNU/Linux"
+VERSION_ID="11"
+VERSION="11 (bullseye)"
+VERSION_CODENAME=bullseye
+ID=debian
+HOME_URL="https://www.debian.org/"
+SUPPORT_URL="https://www.debian.org/support"
+BUG_REPORT_URL="https://bugs.debian.org/"
+`
+
+func TestParseOSRelease(t *testing.T) {
+	want := &osRelease{
+		Name:            "Ubuntu",
+		ID:              "ubuntu",
+		IDLike:          "debian",
+		PrettyName:      "Ubuntu 20.04.2 LTS",
+		Version:         "20.04.2 LTS (Focal Fossa)",
+		VersionID:       "20.04",
+		VersionCodename: "focal",
+	}
+
+	osReleaseFile, err := os.Open("fixtures" + usrLibOSRelease)
+	if err != nil {
+		t.Fatal(err)
+	}
+	got, err := parseOSRelease(osReleaseFile)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !reflect.DeepEqual(want, got) {
+		t.Fatalf("should have %+v osRelease: got %+v", want, got)
+	}
+
+	want = &osRelease{
+		Name:            "Debian GNU/Linux",
+		ID:              "debian",
+		PrettyName:      "Debian GNU/Linux 11 (bullseye)",
+		Version:         "11 (bullseye)",
+		VersionID:       "11",
+		VersionCodename: "bullseye",
+	}
+	got, err = parseOSRelease(strings.NewReader(debianBullseye))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !reflect.DeepEqual(want, got) {
+		t.Fatalf("should have %+v osRelease: got %+v", want, got)
+	}
+}
+
+func TestUpdateStruct(t *testing.T) {
+	wantedOS := &osRelease{
+		Name:            "Ubuntu",
+		ID:              "ubuntu",
+		IDLike:          "debian",
+		PrettyName:      "Ubuntu 20.04.2 LTS",
+		Version:         "20.04.2 LTS (Focal Fossa)",
+		VersionID:       "20.04",
+		VersionCodename: "focal",
+	}
+	wantedVersion := 20.04
+
+	collector, err := NewOSCollector(log.NewNopLogger())
+	if err != nil {
+		t.Fatal(err)
+	}
+	c := collector.(*osReleaseCollector)
+
+	err = c.UpdateStruct("fixtures" + usrLibOSRelease)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !reflect.DeepEqual(wantedOS, c.os) {
+		t.Fatalf("should have %+v osRelease: got %+v", wantedOS, c.os)
+	}
+	if wantedVersion != c.version {
+		t.Errorf("Expected '%v' but got '%v'", wantedVersion, c.version)
+	}
+}

end-to-end-test.sh

@@ -100,6 +100,7 @@ then
 fi
 
 ./node_exporter \
+  --path.rootfs="collector/fixtures" \
   --path.procfs="collector/fixtures/proc" \
   --path.sysfs="collector/fixtures/sys" \
   $(for c in ${enabled_collectors}; do echo --collector.${c}  ; done) \

go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/ema/qdisc v0.0.0-20200603082823-62d0308e3e00
 	github.com/go-kit/log v0.1.0
 	github.com/godbus/dbus v0.0.0-20190402143921-271e53dc4968
+	github.com/hashicorp/go-envparse v0.0.0-20200406174449-d9cfd743a15e
 	github.com/hodgesds/perf-utils v0.2.5
 	github.com/illumos/go-kstat v0.0.0-20210513183136-173c9b0a9973
 	github.com/jsimonetti/rtnetlink v0.0.0-20210713125558-2bfdf1dbdbd6

go.sum

@@ -139,6 +139,8 @@ github.com/google/pprof v0.0.0-20200708004538-1a94d8640e99/go.mod h1:ZgVRPoUq/hf
 github.com/google/renameio v0.1.0/go.mod h1:KWCgfxg9yswjAJkECMjeO8J8rahYeXnNhOm40UhjYkI=
 github.com/googleapis/gax-go/v2 v2.0.4/go.mod h1:0Wqv26UfaUD9n4G6kQubkQ+KchISgw+vpHVxEJEs9eg=
 github.com/googleapis/gax-go/v2 v2.0.5/go.mod h1:DWXyrwAJ9X0FpwwEdw+IPEYBICEFu5mhpdKc/us6bOk=
+github.com/hashicorp/go-envparse v0.0.0-20200406174449-d9cfd743a15e h1:v1d9+AJMP6i4p8BSKNU0InuvmIAdZjQLNN19V86AG4Q=
+github.com/hashicorp/go-envparse v0.0.0-20200406174449-d9cfd743a15e/go.mod h1:/NlxCzN2D4C4L2uDE6ux/h6jM+n98VFQM14nnCIfHJU=
 github.com/hashicorp/golang-lru v0.5.0/go.mod h1:/m3WP610KZHVQ1SGc6re/UDhFvYD7pJ4Ao+sR/qLZy8=
 github.com/hashicorp/golang-lru v0.5.1/go.mod h1:/m3WP610KZHVQ1SGc6re/UDhFvYD7pJ4Ao+sR/qLZy8=
 github.com/hodgesds/perf-utils v0.2.5 h1:X992/V3OaNJRM8Ivcram8Hhxz4JhWiKI0T8iGCJwk2k=