Implement timeouts for all exec command runners

First is to write an internal CombinedOutput and Run function with a
timeout.

Second, the following instances of command runners need to have timeouts:

    plugins/inputs/ping/ping.go
    125:	out, err := c.CombinedOutput()

    plugins/inputs/exec/exec.go
    91:	if err := cmd.Run(); err != nil {

    plugins/inputs/ipmi_sensor/command.go
    31:	err := cmd.Run()

    plugins/inputs/sysstat/sysstat.go
    194:	out, err := cmd.CombinedOutput()

    plugins/inputs/leofs/leofs.go
    185:	defer cmd.Wait()

    plugins/inputs/sysstat/sysstat.go
    282:	if err := cmd.Wait(); err != nil {

closes #1067

internal/internal.go

@@ -2,20 +2,29 @@ package internal
 
 import (
 	"bufio"
+	"bytes"
 	"crypto/rand"
 	"crypto/tls"
 	"crypto/x509"
 	"errors"
 	"fmt"
 	"io/ioutil"
+	"log"
 	"os"
+	"os/exec"
 	"strings"
 	"time"
 	"unicode"
 )
 
 const alphanum string = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
 
+var (
+	TimeoutErr = errors.New("Command timed out.")
+
+	NotImplementedError = errors.New("not implemented yet")
+)
+
 // Duration just wraps time.Duration
 type Duration struct {
 	Duration time.Duration
@@ -33,8 +42,6 @@ func (d *Duration) UnmarshalTOML(b []byte) error {
 	return nil
 }
 
-var NotImplementedError = errors.New("not implemented yet")
-
 // ReadLines reads contents from a file and splits them by new lines.
 // A convenience wrapper to ReadLinesOffsetN(filename, 0, -1).
 func ReadLines(filename string) ([]string, error) {
@@ -139,3 +146,48 @@ func SnakeCase(in string) string {
 
 	return string(out)
 }
+
+// CombinedOutputTimeout runs the given command with the given timeout and
+// returns the combined output of stdout and stderr.
+// If the command times out, it attempts to kill the process.
+func CombinedOutputTimeout(c *exec.Cmd, timeout time.Duration) ([]byte, error) {
+	var b bytes.Buffer
+	c.Stdout = &b
+	c.Stderr = &b
+	if err := c.Start(); err != nil {
+		return nil, err
+	}
+	err := WaitTimeout(c, timeout)
+	return b.Bytes(), err
+}
+
+// RunTimeout runs the given command with the given timeout.
+// If the command times out, it attempts to kill the process.
+func RunTimeout(c *exec.Cmd, timeout time.Duration) error {
+	if err := c.Start(); err != nil {
+		return err
+	}
+	return WaitTimeout(c, timeout)
+}
+
+// WaitTimeout waits for the given command to finish with a timeout.
+// It assumes the command has already been started.
+// If the command times out, it attempts to kill the process.
+func WaitTimeout(c *exec.Cmd, timeout time.Duration) error {
+	timer := time.NewTimer(timeout)
+	done := make(chan error)
+	go func() { done <- c.Wait() }()
+	select {
+	case err := <-done:
+		timer.Stop()
+		return err
+	case <-timer.C:
+		if err := c.Process.Kill(); err != nil {
+			log.Printf("FATAL error killing process: %s", err)
+			return err
+		}
+		// wait for the command to return after killing it
+		<-done
+		return TimeoutErr
+	}
+}

internal/internal_test.go

@@ -1,6 +1,12 @@
 package internal
 
-import "testing"
+import (
+	"os/exec"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
 
 type SnakeTest struct {
 	input  string
@@ -30,3 +36,73 @@ func TestSnakeCase(t *testing.T) {
 		}
 	}
 }
+
+var (
+	sleepbin, _ = exec.LookPath("sleep")
+	echobin, _  = exec.LookPath("echo")
+)
+
+func TestRunTimeout(t *testing.T) {
+	if sleepbin == "" {
+		t.Skip("'sleep' binary not available on OS, skipping.")
+	}
+	cmd := exec.Command(sleepbin, "10")
+	start := time.Now()
+	err := RunTimeout(cmd, time.Millisecond*20)
+	elapsed := time.Since(start)
+
+	assert.Equal(t, TimeoutErr, err)
+	// Verify that command gets killed in 20ms, with some breathing room
+	assert.True(t, elapsed < time.Millisecond*75)
+}
+
+func TestCombinedOutputTimeout(t *testing.T) {
+	if sleepbin == "" {
+		t.Skip("'sleep' binary not available on OS, skipping.")
+	}
+	cmd := exec.Command(sleepbin, "10")
+	start := time.Now()
+	_, err := CombinedOutputTimeout(cmd, time.Millisecond*20)
+	elapsed := time.Since(start)
+
+	assert.Equal(t, TimeoutErr, err)
+	// Verify that command gets killed in 20ms, with some breathing room
+	assert.True(t, elapsed < time.Millisecond*75)
+}
+
+func TestCombinedOutput(t *testing.T) {
+	if echobin == "" {
+		t.Skip("'echo' binary not available on OS, skipping.")
+	}
+	cmd := exec.Command(echobin, "foo")
+	out, err := CombinedOutputTimeout(cmd, time.Second)
+
+	assert.NoError(t, err)
+	assert.Equal(t, "foo\n", string(out))
+}
+
+// test that CombinedOutputTimeout and exec.Cmd.CombinedOutput return
+// the same output from a failed command.
+func TestCombinedOutputError(t *testing.T) {
+	if sleepbin == "" {
+		t.Skip("'sleep' binary not available on OS, skipping.")
+	}
+	cmd := exec.Command(sleepbin, "foo")
+	expected, err := cmd.CombinedOutput()
+
+	cmd2 := exec.Command(sleepbin, "foo")
+	actual, err := CombinedOutputTimeout(cmd2, time.Second)
+
+	assert.Error(t, err)
+	assert.Equal(t, expected, actual)
+}
+
+func TestRunError(t *testing.T) {
+	if sleepbin == "" {
+		t.Skip("'sleep' binary not available on OS, skipping.")
+	}
+	cmd := exec.Command(sleepbin, "foo")
+	err := RunTimeout(cmd, time.Second)
+
+	assert.Error(t, err)
+}

plugins/inputs/exec/exec.go

@@ -6,10 +6,12 @@ import (
 	"os/exec"
 	"sync"
 	"syscall"
+	"time"
 
 	"github.com/gonuts/go-shellquote"
 
 	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/internal"
 	"github.com/influxdata/telegraf/plugins/inputs"
 	"github.com/influxdata/telegraf/plugins/parsers"
 	"github.com/influxdata/telegraf/plugins/parsers/nagios"
@@ -19,6 +21,9 @@ const sampleConfig = `
   ## Commands array
   commands = ["/tmp/test.sh", "/usr/bin/mycollector --foo=bar"]
 
+  ## Timeout for each command to complete.
+  timeout = "5s"
+
   ## measurement name suffix (for separating different commands)
   name_suffix = "_mycollector"
 
@@ -32,6 +37,7 @@ const sampleConfig = `
 type Exec struct {
 	Commands []string
 	Command  string
+	Timeout  internal.Duration
 
 	parser parsers.Parser
 
@@ -43,7 +49,8 @@ type Exec struct {
 
 func NewExec() *Exec {
 	return &Exec{
-		runner: CommandRunner{},
+		runner:  CommandRunner{},
+		Timeout: internal.Duration{Duration: time.Second * 5},
 	}
 }
 
@@ -73,7 +80,11 @@ func AddNagiosState(exitCode error, acc telegraf.Accumulator) error {
 	return nil
 }
 
-func (c CommandRunner) Run(e *Exec, command string, acc telegraf.Accumulator) ([]byte, error) {
+func (c CommandRunner) Run(
+	e *Exec,
+	command string,
+	acc telegraf.Accumulator,
+) ([]byte, error) {
 	split_cmd, err := shellquote.Split(command)
 	if err != nil || len(split_cmd) == 0 {
 		return nil, fmt.Errorf("exec: unable to parse command, %s", err)
@@ -84,7 +95,7 @@ func (c CommandRunner) Run(e *Exec, command string, acc telegraf.Accumulator) ([
 	var out bytes.Buffer
 	cmd.Stdout = &out
 
-	if err := cmd.Run(); err != nil {
+	if err := internal.RunTimeout(cmd, e.Timeout.Duration); err != nil {
 		switch e.parser.(type) {
 		case *nagios.NagiosParser:
 			AddNagiosState(err, acc)

plugins/inputs/ipmi_sensor/command.go

@@ -1,10 +1,12 @@
 package ipmi_sensor
 
 import (
-	"bytes"
 	"fmt"
 	"os/exec"
 	"strings"
+	"time"
+
+	"github.com/influxdata/telegraf/internal"
 )
 
 type CommandRunner struct{}
@@ -18,21 +20,16 @@ func (t CommandRunner) cmd(conn *Connection, args ...string) *exec.Cmd {
 	}
 
 	return exec.Command(path, opts...)
-
 }
 
 func (t CommandRunner) Run(conn *Connection, args ...string) (string, error) {
 	cmd := t.cmd(conn, args...)
-	var stdout bytes.Buffer
-	var stderr bytes.Buffer
-	cmd.Stdout = &stdout
-	cmd.Stderr = &stderr
 
-	err := cmd.Run()
+	output, err := internal.CombinedOutputTimeout(cmd, time.Second*5)
 	if err != nil {
 		return "", fmt.Errorf("run %s %s: %s (%s)",
-			cmd.Path, strings.Join(cmd.Args, " "), stderr.String(), err)
+			cmd.Path, strings.Join(cmd.Args, " "), string(output), err)
 	}
 
-	return stdout.String(), err
+	return string(output), err
 }

plugins/inputs/leofs/leofs.go

@@ -3,13 +3,16 @@ package leofs
 import (
 	"bufio"
 	"fmt"
-	"github.com/influxdata/telegraf"
-	"github.com/influxdata/telegraf/plugins/inputs"
 	"net/url"
 	"os/exec"
 	"strconv"
 	"strings"
 	"sync"
+	"time"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/internal"
+	"github.com/influxdata/telegraf/plugins/inputs"
 )
 
 const oid = ".1.3.6.1.4.1.35450"
@@ -175,14 +178,18 @@ func (l *LeoFS) Gather(acc telegraf.Accumulator) error {
 	return outerr
 }
 
-func (l *LeoFS) gatherServer(endpoint string, serverType ServerType, acc telegraf.Accumulator) error {
+func (l *LeoFS) gatherServer(
+	endpoint string,
+	serverType ServerType,
+	acc telegraf.Accumulator,
+) error {
 	cmd := exec.Command("snmpwalk", "-v2c", "-cpublic", endpoint, oid)
 	stdout, err := cmd.StdoutPipe()
 	if err != nil {
 		return err
 	}
 	cmd.Start()
-	defer cmd.Wait()
+	defer internal.WaitTimeout(cmd, time.Second*5)
 	scanner := bufio.NewScanner(stdout)
 	if !scanner.Scan() {
 		return fmt.Errorf("Unable to retrieve the node name")

plugins/inputs/ping/ping.go

@@ -9,15 +9,17 @@ import (
 	"strconv"
 	"strings"
 	"sync"
+	"time"
 
 	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/internal"
 	"github.com/influxdata/telegraf/plugins/inputs"
 )
 
 // HostPinger is a function that runs the "ping" function using a list of
 // passed arguments. This can be easily switched with a mocked ping function
 // for unit test purposes (see ping_test.go)
-type HostPinger func(args ...string) (string, error)
+type HostPinger func(timeout float64, args ...string) (string, error)
 
 type Ping struct {
 	// Interval at which to ping (ping -i <INTERVAL>)
@@ -74,7 +76,7 @@ func (p *Ping) Gather(acc telegraf.Accumulator) error {
 		go func(u string) {
 			defer wg.Done()
 			args := p.args(u)
-			out, err := p.pingHost(args...)
+			out, err := p.pingHost(p.Timeout, args...)
 			if err != nil {
 				// Combine go err + stderr output
 				errorChannel <- errors.New(
@@ -116,13 +118,14 @@ func (p *Ping) Gather(acc telegraf.Accumulator) error {
 	return errors.New(strings.Join(errorStrings, "\n"))
 }
 
-func hostPinger(args ...string) (string, error) {
+func hostPinger(timeout float64, args ...string) (string, error) {
 	bin, err := exec.LookPath("ping")
 	if err != nil {
 		return "", err
 	}
 	c := exec.Command(bin, args...)
-	out, err := c.CombinedOutput()
+	out, err := internal.CombinedOutputTimeout(c,
+		time.Second*time.Duration(timeout+1))
 	return string(out), err
 }
 

plugins/inputs/ping/ping_test.go

@@ -124,7 +124,7 @@ func TestArgs(t *testing.T) {
 		"Expected: %s Actual: %s", expected, actual)
 }
 
-func mockHostPinger(args ...string) (string, error) {
+func mockHostPinger(timeout float64, args ...string) (string, error) {
 	return linuxPingOutput, nil
 }
 
@@ -161,7 +161,7 @@ PING www.google.com (216.58.218.164) 56(84) bytes of data.
 rtt min/avg/max/mdev = 35.225/44.033/51.806/5.325 ms
 `
 
-func mockLossyHostPinger(args ...string) (string, error) {
+func mockLossyHostPinger(timeout float64, args ...string) (string, error) {
 	return lossyPingOutput, nil
 }
 
@@ -192,7 +192,7 @@ Request timeout for icmp_seq 0
 2 packets transmitted, 0 packets received, 100.0% packet loss
 `
 
-func mockErrorHostPinger(args ...string) (string, error) {
+func mockErrorHostPinger(timeout float64, args ...string) (string, error) {
 	return errorPingOutput, errors.New("No packets received")
 }
 
@@ -215,7 +215,7 @@ func TestBadPingGather(t *testing.T) {
 	acc.AssertContainsTaggedFields(t, "ping", fields, tags)
 }
 
-func mockFatalHostPinger(args ...string) (string, error) {
+func mockFatalHostPinger(timeout float64, args ...string) (string, error) {
 	return fatalPingOutput, errors.New("So very bad")
 }