2527 Allow collecting of host stats within docker containers by enabl…

…e procfs and sysfs location overrides

plugins/inputs/system/LINUX_SYSCTL_FS_README.md

@@ -7,3 +7,8 @@ Example output:
 ```
 > linux_sysctl_fs,host=foo dentry-want-pages=0i,file-max=44222i,aio-max-nr=65536i,inode-preshrink-nr=0i,dentry-nr=64340i,dentry-unused-nr=55274i,file-nr=1568i,aio-nr=0i,inode-nr=35952i,inode-free-nr=12957i,dentry-age-limit=45i 1490982022000000000
 ```
+### Configuration:
+The sysctl path can be redefined by specifying the prefix of the path as an environment variable.
+ `SYS_PATH_PREFIX` the plugin will retrieve process information from the specified location.
+
+`docker run -v /proc:/rootfs/proc:ro -e SYS_PATH_PREFIX=/rootfs`

plugins/inputs/system/PROCESSES_README.md

@@ -14,6 +14,11 @@ it requires access to execute `ps`.
   # no configuration
 ```
 
+Another possible configuration is to define a prefix for resolving the procfs (/proc) location.
+Using the environment variable `PROC_PATH_PREFIX` the plugin will retrieve process information from the specified location.
+
+`docker run -v /proc:/rootfs/proc:ro -e PROC_PATH_PREFIX=/rootfs`
+
 ### Measurements & Fields:
 
 - processes

plugins/inputs/system/linux_sysctl_fs.go

@@ -3,6 +3,7 @@ package system
 import (
 	"bytes"
 	"io/ioutil"
+	"os"
 	"strconv"
 
 	"github.com/influxdata/telegraf"
@@ -23,6 +24,9 @@ func (_ SysctlFS) Description() string {
 func (_ SysctlFS) SampleConfig() string {
 	return sysctlFSSampleConfig
 }
+func OSGetEnv(key string) string {
+	return os.Getenv(key)
+}
 
 func (sfs *SysctlFS) gatherList(file string, fields map[string]interface{}, fieldNames ...string) error {
 	bs, err := ioutil.ReadFile(sfs.path + "/" + file)
@@ -82,7 +86,7 @@ func (sfs *SysctlFS) Gather(acc telegraf.Accumulator) error {
 func init() {
 	inputs.Add("linux_sysctl_fs", func() telegraf.Input {
 		return &SysctlFS{
-			path: "/proc/sys/fs",
+			path: OSGetEnv("SYS_PATH_PREFIX") + "/proc/sys/fs",
 		}
 	})
 }

plugins/inputs/system/processes.go

@@ -20,6 +20,7 @@ import (
 
 type Processes struct {
 	execPS       func() ([]byte, error)
+	osGetEnv     func(key string) string
 	readProcFile func(filename string) ([]byte, error)
 
 	forcePS   bool
@@ -37,7 +38,7 @@ func (p *Processes) Gather(acc telegraf.Accumulator) error {
 	fields := getEmptyFields()
 
 	// Decide if we will use 'ps' to get stats (use procfs otherwise)
-	usePS := true
+	usePS := false
 	if runtime.GOOS == "linux" {
 		usePS = false
 	}
@@ -132,14 +133,13 @@ func (p *Processes) gatherFromPS(fields map[string]interface{}) error {
 
 // get process states from /proc/(pid)/stat files
 func (p *Processes) gatherFromProc(fields map[string]interface{}) error {
-	filenames, err := filepath.Glob("/proc/[0-9]*/stat")
+	filenames, err := filepath.Glob(p.osGetEnv("PROC_PATH_PREFIX") + "/proc/[0-9]*/stat")
 	if err != nil {
 		return err
 	}
 
 	for _, filename := range filenames {
 		_, err := os.Stat(filename)
-
 		data, err := p.readProcFile(filename)
 		if err != nil {
 			return err
@@ -209,6 +209,10 @@ func readProcFile(filename string) ([]byte, error) {
 	return data, nil
 }
 
+func osGetEnv(key string) string {
+	return os.Getenv(key)
+}
+
 func execPS() ([]byte, error) {
 	bin, err := exec.LookPath("ps")
 	if err != nil {
@@ -227,6 +231,7 @@ func init() {
 	inputs.Add("processes", func() telegraf.Input {
 		return &Processes{
 			execPS:       execPS,
+			osGetEnv:     osGetEnv,
 			readProcFile: readProcFile,
 		}
 	})