fix: patched intel rdt to allow sudo (#9527)

Co-authored-by: Joe Guo <joe.guo@canonical.com>

plugins/inputs/intel_rdt/README.md

@@ -24,6 +24,29 @@ Note: pqos tool needs root privileges to work properly.
 
 Metrics will be constantly reported from the following `pqos` commands within the given interval:
 
+#### If telegraf does not run as the root user
+
+The `pqos` binary needs to run as root.  If telegraf is running as a non-root user, you may enable sudo
+to allow `pqos` to run correctly.
+The `pqos` command requires root level access to run.  There are two options to
+overcome this if you run telegraf as a non-root user.
+
+It is possible to update the pqos binary with setuid using `chmod u+s
+/path/to/pqos`.  This approach is simple and requires no modification to the
+Telegraf configuration, however pqos is not a read-only tool and there are
+security implications for making such a command setuid root.
+
+Alternately, you may enable sudo to allow `pqos` to run correctly, as follows:
+
+Add the following to your sudoers file (assumes telegraf runs as a user named `telegraf`):
+
+```
+telegraf ALL=(ALL) NOPASSWD:/usr/sbin/pqos -r --iface-os --mon-file-type=csv --mon-interval=*
+```
+
+If you wish to use sudo, you must also add `use_sudo = true` to the Telegraf
+configuration (see below).
+
 #### In case of cores monitoring:
 ```
 pqos -r --iface-os --mon-file-type=csv --mon-interval=INTERVAL --mon-core=all:[CORES]\;mbt:[CORES]
@@ -76,6 +99,10 @@ More about Intel RDT: https://www.intel.com/content/www/us/en/architecture-and-t
   ## Mandatory if cores aren't set and forbidden if cores are specified.
   ## e.g. ["qemu", "pmd"]
   # processes = ["process"]
+
+  ## Specify if the pqos process should be called with sudo.
+  ## Mandatory if the telegraf process does not run as root.
+  # use_sudo = false
 ```
 
 ### Exposed metrics

plugins/inputs/intel_rdt/intel_rdt.go

@@ -14,6 +14,7 @@ import (
 	"strconv"
 	"strings"
 	"sync"
+	"syscall"
 	"time"
 
 	"github.com/google/go-cmp/cmp"
@@ -46,6 +47,7 @@ type IntelRDT struct {
 	Processes        []string `toml:"processes"`
 	SamplingInterval int32    `toml:"sampling_interval"`
 	ShortenedMetrics bool     `toml:"shortened_metrics"`
+	UseSudo          bool     `toml:"use_sudo"`
 
 	Log              telegraf.Logger  `toml:"-"`
 	Publisher        Publisher        `toml:"-"`
@@ -97,6 +99,10 @@ func (r *IntelRDT) SampleConfig() string {
 	## Mandatory if cores aren't set and forbidden if cores are specified.
 	## e.g. ["qemu", "pmd"]
 	# processes = ["process"]
+
+	## Specify if the pqos process should be called with sudo.
+	## Mandatory if the telegraf process does not run as root.
+	# use_sudo = false
 `
 }
 
@@ -254,6 +260,12 @@ func (r *IntelRDT) readData(ctx context.Context, args []string, processesPIDsAss
 
 	cmd := exec.Command(r.PqosPath, append(args)...)
 
+	if r.UseSudo {
+		// run pqos with `/bin/sh -c "sudo /path/to/pqos ..."`
+		args = []string{"-c", fmt.Sprintf("sudo %s %s", r.PqosPath, strings.Replace(strings.Join(args, " "), ";", "\\;", -1))}
+		cmd = exec.Command("/bin/sh", args...)
+	}
+
 	cmdReader, err := cmd.StdoutPipe()
 	if err != nil {
 		r.errorChan <- err
@@ -334,14 +346,30 @@ func (r *IntelRDT) processOutput(cmdReader io.ReadCloser, processesPIDsAssociati
 }
 
 func shutDownPqos(pqos *exec.Cmd) error {
+	timeout := time.Second * 2
+
 	if pqos.Process != nil {
-		err := pqos.Process.Signal(os.Interrupt)
+		// try to send interrupt signal, ignore err for now
-		if err != nil {
+		_ = pqos.Process.Signal(os.Interrupt)
-			err = pqos.Process.Kill()
+
-			if err != nil {
+		// wait and constantly check if pqos is still running
-				return fmt.Errorf("failed to shut down pqos: %v", err)
+		ctx, cancel := context.WithTimeout(context.Background(), timeout)
+		defer cancel()
+		for {
+			if err := pqos.Process.Signal(syscall.Signal(0)); err == os.ErrProcessDone {
+				return nil
+			} else if ctx.Err() != nil {
+				break
 			}
 		}
+
+		// if pqos is still running after some period, try to kill it
+		// this will send SIGTERM to pqos, and leave garbage in `/sys/fs/resctrl/mon_groups`
+		// fixed in https://github.com/intel/intel-cmt-cat/issues/197
+		err := pqos.Process.Kill()
+		if err != nil {
+			return fmt.Errorf("failed to shut down pqos: %v", err)
+		}
 	}
 	return nil
 }