Bugfix/procstat adds new procstat metric about pgrep search

internal/internal.go

@@ -11,6 +11,7 @@ import (
 	"os/exec"
 	"strconv"
 	"strings"
+	"syscall"
 	"time"
 	"unicode"
 )
@@ -193,3 +194,15 @@ func RandomSleep(max time.Duration, shutdown chan struct{}) {
 		return
 	}
 }
+
+// Exit status takes the error from exec.Command
+// and returns the exit status and true
+// if error is not exit status, will return 0 and false
+func ExitStatus(err error) (int, bool) {
+	if exiterr, ok := err.(*exec.ExitError); ok {
+		if status, ok := exiterr.Sys().(syscall.WaitStatus); ok {
+			return status.ExitStatus(), true
+		}
+	}
+	return 0, false
+}

plugins/inputs/procstat/pgrep.go

@@ -6,6 +6,8 @@ import (
 	"os/exec"
 	"strconv"
 	"strings"
+
+	"github.com/influxdata/telegraf/internal"
 )
 
 // Implemention of PIDGatherer that execs pgrep to find processes
@@ -62,6 +64,12 @@ func find(path string, args []string) ([]PID, error) {
 
 func run(path string, args []string) (string, error) {
 	out, err := exec.Command(path, args...).Output()
+
+	//if exit code 1, ie no processes found, do not return error
+	if i, _ := internal.ExitStatus(err); i == 1 {
+		return "", nil
+	}
+
 	if err != nil {
 		return "", fmt.Errorf("Error running %s: %s", path, err)
 	}

plugins/inputs/procstat/procstat.go

@@ -97,7 +97,7 @@ func (p *Procstat) Gather(acc telegraf.Accumulator) error {
 		p.createProcess = defaultProcess
 	}
 
-	procs, err := p.updateProcesses(p.procs)
+	procs, err := p.updateProcesses(acc, p.procs)
 	if err != nil {
 		acc.AddError(fmt.Errorf("E! Error: procstat getting process, exe: [%s] pidfile: [%s] pattern: [%s] user: [%s] %s",
 			p.Exe, p.PidFile, p.Pattern, p.User, err.Error()))
@@ -230,8 +230,8 @@ func (p *Procstat) addMetrics(proc Process, acc telegraf.Accumulator) {
 }
 
 // Update monitored Processes
-func (p *Procstat) updateProcesses(prevInfo map[PID]Process) (map[PID]Process, error) {
-	pids, tags, err := p.findPids()
+func (p *Procstat) updateProcesses(acc telegraf.Accumulator, prevInfo map[PID]Process) (map[PID]Process, error) {
+	pids, tags, err := p.findPids(acc)
 	if err != nil {
 		return nil, err
 	}
@@ -281,9 +281,9 @@ func (p *Procstat) getPIDFinder() (PIDFinder, error) {
 }
 
 // Get matching PIDs and their initial tags
-func (p *Procstat) findPids() ([]PID, map[string]string, error) {
+func (p *Procstat) findPids(acc telegraf.Accumulator) ([]PID, map[string]string, error) {
 	var pids []PID
-	var tags map[string]string
+	tags := make(map[string]string)
 	var err error
 
 	f, err := p.getPIDFinder()
@@ -313,7 +313,18 @@ func (p *Procstat) findPids() ([]PID, map[string]string, error) {
 		err = fmt.Errorf("Either exe, pid_file, user, pattern, systemd_unit, or cgroup must be specified")
 	}
 
-	return pids, tags, err
+	rTags := make(map[string]string)
+	for k, v := range tags {
+		rTags[k] = v
+	}
+
+	//adds a metric with info on the pgrep query
+	fields := make(map[string]interface{})
+	tags["pid_finder"] = p.PidFinder
+	fields["pid_count"] = len(pids)
+	acc.AddFields("procstat_lookup", fields, tags)
+
+	return pids, rTags, err
 }
 
 // execCommand is so tests can mock out exec.Command usage.

plugins/inputs/procstat/procstat_test.go

@@ -343,7 +343,8 @@ func TestGather_systemdUnitPIDs(t *testing.T) {
 		createPIDFinder: pidFinder([]PID{}, nil),
 		SystemdUnit:     "TestGather_systemdUnitPIDs",
 	}
-	pids, tags, err := p.findPids()
+	var acc testutil.Accumulator
+	pids, tags, err := p.findPids(&acc)
 	require.NoError(t, err)
 	assert.Equal(t, []PID{11408}, pids)
 	assert.Equal(t, "TestGather_systemdUnitPIDs", tags["systemd_unit"])
@@ -364,8 +365,20 @@ func TestGather_cgroupPIDs(t *testing.T) {
 		createPIDFinder: pidFinder([]PID{}, nil),
 		CGroup:          td,
 	}
-	pids, tags, err := p.findPids()
+	var acc testutil.Accumulator
+	pids, tags, err := p.findPids(&acc)
 	require.NoError(t, err)
 	assert.Equal(t, []PID{1234, 5678}, pids)
 	assert.Equal(t, td, tags["cgroup"])
 }
+
+func TestProcstatLookupMetric(t *testing.T) {
+	p := Procstat{
+		createPIDFinder: pidFinder([]PID{543}, nil),
+		Exe:             "-Gsys",
+	}
+	var acc testutil.Accumulator
+	err := acc.GatherError(p.Gather)
+	require.NoError(t, err)
+	require.Equal(t, len(p.procs)+1, len(acc.Metrics))
+}