CP-11399: Go Linux guest agent for XenServer

This is the reviewed and tested Go guest agent for XenServer Linux guests.

Go guest agent is a static linked binary without any dependency (e.g. Bash or Python execution environment) with below benefits:
1. Cross platform, Go version works well with all kinds Linux distributions (i386 and x86_64) with the porting ability to arm, FreeBSD, Darwin OS etc.
2. Standalone binary, works well with some restricted environment for example, CoreOS and Boot2Docker Linux
3. Easy to maintain and structured design, with Golang's nature

Change history:
1: Refined Rob Robert's comments.
2: Add unit test for xenstoreclient and refact folder structure.
3: Refined codes according to Robert's comments
4: To run 32bit xe-guest-agent in Linux 64bit OS(eg, CoreOS):
we need
  4.1 - Switch to ip/ifconfig CLI tool instead of net package
  4.2 - Switch to log package instead of syslog package

Signed-off-by: phus lu <phus.lu@citrix.com>

3 files changed, 358 insertions, 0 deletions

diff --git a/guestmetric/guestmetric.go b/guestmetric/guestmetric.go
new file mode 100644
index 0000000..836f105
--- /dev/null
+++ b/guestmetric/guestmetric.go
@@ -0,0 +1,38 @@
+package guestmetric
+
+import (
+	"bytes"
+	"os/exec"
+)
+
+type GuestMetric map[string]string
+
+type CollectFunc func() (GuestMetric, error)
+
+type GuestMetricsCollector interface {
+	CollectOS() (GuestMetric, error)
+	CollectMisc() (GuestMetric, error)
+	CollectNetworkAddr() (GuestMetric, error)
+	CollectDisk() (GuestMetric, error)
+	CollectMemory() (GuestMetric, error)
+}
+
+func runCmd(name string, args ...string) (output string, err error) {
+	cmd := exec.Command(name, args...)
+	var out bytes.Buffer
+	cmd.Stdout = &out
+	err = cmd.Run()
+	if err != nil {
+		return "", err
+	}
+	output = out.String()
+	return output, nil
+}
+
+func prefixKeys(prefix string, m GuestMetric) GuestMetric {
+	m1 := make(GuestMetric, 0)
+	for k, v := range m {
+		m1[prefix+k] = v
+	}
+	return m1
+}
diff --git a/guestmetric/guestmetric_linux.go b/guestmetric/guestmetric_linux.go
new file mode 100644
index 0000000..3970da4
--- /dev/null
+++ b/guestmetric/guestmetric_linux.go
@@ -0,0 +1,257 @@
+package guestmetric
+
+import (
+	xenstoreclient "../xenstoreclient"
+	"bufio"
+	"bytes"
+	"fmt"
+	"os"
+	"path/filepath"
+	"regexp"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+type Collector struct {
+	Client xenstoreclient.XenStoreClient
+	Ballon bool
+	Debug  bool
+}
+
+func (c *Collector) CollectOS() (GuestMetric, error) {
+	current := make(GuestMetric, 0)
+	f, err := os.OpenFile("/var/cache/xe-linux-distribution", os.O_RDONLY, 0666)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if strings.Contains(line, "=") {
+			parts := strings.SplitN(line, "=", 2)
+			k := strings.TrimSpace(parts[0])
+			v := strings.TrimSpace(strings.Trim(strings.TrimSpace(parts[1]), "\""))
+			current[k] = v
+		}
+	}
+	return prefixKeys("data/", current), nil
+}
+
+func (c *Collector) CollectMisc() (GuestMetric, error) {
+	current := make(GuestMetric, 0)
+	if c.Ballon {
+		current["control/feature-balloon"] = "1"
+	} else {
+		current["control/feature-balloon"] = "0"
+	}
+	current["attr/PVAddons/Installed"] = "1"
+	current["attr/PVAddons/MajorVersion"] = "@PRODUCT_MAJOR_VERSION@"
+	current["attr/PVAddons/MinorVersion"] = "@PRODUCT_MINOR_VERSION@"
+	current["attr/PVAddons/MicroVersion"] = "@PRODUCT_MICRO_VERSION@"
+	current["attr/PVAddons/BuildVersion"] = "@NUMERIC_BUILD_NUMBER@"
+
+	return current, nil
+}
+
+func (c *Collector) CollectMemory() (GuestMetric, error) {
+	current := make(GuestMetric, 0)
+	f, err := os.OpenFile("/proc/meminfo", os.O_RDONLY, 0666)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		parts := regexp.MustCompile(`\w+`).FindAllString(scanner.Text(), -1)
+		switch parts[0] {
+		case "MemTotal":
+			current["meminfo_total"] = parts[1]
+		case "MemFree":
+			current["meminfo_free"] = parts[1]
+		}
+	}
+	return prefixKeys("data/", current), nil
+}
+
+func EnumNetworkAddresses(iface string) (GuestMetric, error) {
+	const (
+		IP_RE   string = `(\d{1,3}\.){3}\d{1,3}`
+		IPV6_RE string = `[\da-f:]+[\da-f]`
+	)
+
+	var (
+		IP_IPV4_ADDR_RE       = regexp.MustCompile(`inet\s*(` + IP_RE + `).*\se[a-zA-Z0-9]+\s`)
+		IP_IPV6_ADDR_RE       = regexp.MustCompile(`inet6\s*(` + IPV6_RE + `)`)
+		IFCONFIG_IPV4_ADDR_RE = regexp.MustCompile(`inet addr:\s*(` + IP_RE + `)`)
+		IFCONFIG_IPV6_ADDR_RE = regexp.MustCompile(`inet6 addr:\s*(` + IPV6_RE + `)`)
+	)
+
+	d := make(GuestMetric, 0)
+
+	var v4re, v6re *regexp.Regexp
+	var out string
+	var err error
+	if out, err = runCmd("ip", "addr", "show", iface); err == nil {
+		v4re = IP_IPV4_ADDR_RE
+		v6re = IP_IPV6_ADDR_RE
+	} else if out, err = runCmd("ifconfig", iface); err == nil {
+		v4re = IFCONFIG_IPV4_ADDR_RE
+		v6re = IFCONFIG_IPV6_ADDR_RE
+	} else {
+		return nil, fmt.Errorf("Cannot found ip/ifconfig command")
+	}
+
+	m := v4re.FindAllStringSubmatch(out, -1)
+	if m != nil {
+		for _, parts := range m {
+			d["ip"] = parts[1]
+		}
+	}
+	m = v6re.FindAllStringSubmatch(out, -1)
+	if m != nil {
+		for i, parts := range m {
+			d[fmt.Sprintf("ipv6/%d/addr", i)] = parts[1]
+		}
+	}
+	return d, nil
+}
+
+func (c *Collector) CollectNetworkAddr() (GuestMetric, error) {
+	current := make(GuestMetric, 0)
+
+	paths, err := filepath.Glob("/sys/class/net/e*")
+	if err != nil {
+		return nil, err
+	}
+
+	for _, path := range paths {
+		iface := filepath.Base(path)
+		if addrs, err := EnumNetworkAddresses(iface); err == nil {
+			for tag, addr := range addrs {
+				current[fmt.Sprintf("%s/%s", iface, tag)] = addr
+			}
+		}
+	}
+	return prefixKeys("attr/", current), nil
+}
+
+func readSysfs(filename string) (string, error) {
+	f, err := os.OpenFile(filename, os.O_RDONLY, 0666)
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+	scanner := bufio.NewScanner(f)
+	scanner.Scan()
+	return scanner.Text(), nil
+}
+
+func (c *Collector) CollectDisk() (GuestMetric, error) {
+	pi := make(GuestMetric, 0)
+
+	disks := make([]string, 0)
+	paths, err := filepath.Glob("/sys/block/*/device")
+	if err != nil {
+		return nil, err
+	}
+	for _, path := range paths {
+		disk := filepath.Base(strings.TrimSuffix(filepath.Dir(path), "/"))
+		disks = append(disks, disk)
+	}
+
+	var sortedDisks sort.StringSlice = disks
+	sortedDisks.Sort()
+
+	part_idx := 0
+	for _, disk := range sortedDisks[:] {
+		paths, err = filepath.Glob(fmt.Sprintf("/dev/%s?*", disk))
+		if err != nil {
+			return nil, err
+		}
+		for _, path := range paths {
+			p := filepath.Base(path)
+			line, err := readSysfs(fmt.Sprintf("/sys/block/%s/%s/size", disk, p))
+			if err != nil {
+				return nil, err
+			}
+			size, err := strconv.ParseInt(line, 10, 64)
+			if err != nil {
+				return nil, err
+			}
+			blocksize := 512
+			if bs, err := readSysfs(fmt.Sprintf("/sys/block/%s/queue/physical_block_size", p)); err == nil {
+				if bs1, err := strconv.Atoi(bs); err == nil {
+					blocksize = bs1
+				}
+			}
+			real_dev := ""
+			if c.Client != nil {
+				nodename, err := readSysfs(fmt.Sprintf("/sys/block/%s/device/nodename", disk))
+				if err != nil {
+					return nil, err
+				}
+				backend, err := c.Client.Read(fmt.Sprintf("%s/backend", nodename))
+				if err != nil {
+					return nil, err
+				}
+				real_dev, err = c.Client.Read(fmt.Sprintf("%s/dev", backend))
+				if err != nil {
+					return nil, err
+				}
+			}
+			name := path
+			blkid, err := runCmd("blkid", "-s", "UUID", path)
+			if err != nil {
+				return nil, err
+			}
+			if strings.Contains(blkid, "=") {
+				parts := strings.SplitN(strings.TrimSpace(blkid), "=", 2)
+				name = fmt.Sprintf("%s(%s)", name, strings.Trim(parts[1], "\""))
+			}
+			i := map[string]string{
+				"extents/0": real_dev,
+				"name":      name,
+				"size":      strconv.FormatInt(size*int64(blocksize), 10),
+			}
+			output, err := runCmd("pvs", "--noheadings", "--units", "b", path)
+			if err == nil && output != "" {
+				parts := regexp.MustCompile(`\s+`).Split(output, -1)[1:]
+				i["free"] = strings.TrimSpace(parts[5])[:len(parts[5])-1]
+				i["filesystem"] = strings.TrimSpace(parts[2])
+				i["mount_points/0"] = "[LVM]"
+			} else {
+				output, err = runCmd("mount")
+				if err == nil {
+					m := regexp.MustCompile(`(?m)^(\S+) on (\S+) type (\S+)`).FindAllStringSubmatch(output, -1)
+					if m != nil {
+						for _, parts := range m {
+							if parts[1] == path {
+								i["mount_points/0"] = parts[2]
+								i["filesystem"] = parts[3]
+								break
+							}
+						}
+					}
+				}
+				output, err = runCmd("df", path)
+				if err == nil {
+					scanner := bufio.NewScanner(bytes.NewReader([]byte(output)))
+					scanner.Scan()
+					scanner.Scan()
+					parts := regexp.MustCompile(`\s+`).Split(scanner.Text(), -1)
+					free, err := strconv.ParseInt(parts[3], 10, 64)
+					if err == nil {
+						i["free"] = strconv.FormatInt(free*1024, 10)
+					}
+				}
+			}
+			for k, v := range i {
+				pi[fmt.Sprintf("data/volumes/%d/%s", part_idx, k)] = v
+			}
+			part_idx += 1
+		}
+	}
+	return pi, nil
+}
diff --git a/guestmetric/guestmetric_test.go b/guestmetric/guestmetric_test.go
new file mode 100644
index 0000000..dcc5384
--- /dev/null
+++ b/guestmetric/guestmetric_test.go
@@ -0,0 +1,63 @@
+package guestmetric
+
+import (
+	"testing"
+)
+
+func TestCollector(t *testing.T) {
+	c := Collector{
+		Client: nil,
+	}
+
+	funcs := []CollectFunc{
+		c.CollectDisk,
+		c.CollectMemory,
+		c.CollectMisc,
+		c.CollectNetworkAddr,
+	}
+
+	for _, f := range funcs {
+		metric, err := f()
+		if err != nil {
+			t.Errorf("%#v error: %#v\n", f, err)
+		}
+		t.Logf("%#v return %#v", f, metric)
+	}
+}
+
+func doBenchmark(b *testing.B, f CollectFunc) {
+	b.Logf("doBenchmark 1000 for %#v", f)
+	for i := 0; i < 1000; i++ {
+		if _, err := f(); err != nil {
+			b.Errorf("%#v error: %#v\n", f, err)
+		}
+	}
+}
+
+func BenchmarkCollectorDisk(b *testing.B) {
+	c := Collector{
+		Client: nil,
+	}
+	doBenchmark(b, c.CollectDisk)
+}
+
+func BenchmarkCollectMemory(b *testing.B) {
+	c := Collector{
+		Client: nil,
+	}
+	doBenchmark(b, c.CollectMemory)
+}
+
+func BenchmarkCollectMisc(b *testing.B) {
+	c := Collector{
+		Client: nil,
+	}
+	doBenchmark(b, c.CollectMisc)
+}
+
+func BenchmarkCollectNetwork(b *testing.B) {
+	c := Collector{
+		Client: nil,
+	}
+	doBenchmark(b, c.CollectNetworkAddr)
+}