Add exec output plugin (#6267)

README.md

@@ -367,6 +367,7 @@ For documentation on the latest development code see the [documentation index][d
 * [datadog](./plugins/outputs/datadog)
 * [discard](./plugins/outputs/discard)
 * [elasticsearch](./plugins/outputs/elasticsearch)
+* [exec](./plugins/output/exec)
 * [file](./plugins/outputs/file)
 * [graphite](./plugins/outputs/graphite)
 * [graylog](./plugins/outputs/graylog)

internal/internal.go

@@ -230,17 +230,17 @@ func WaitTimeout(c *exec.Cmd, timeout time.Duration) error {
 	timer := time.AfterFunc(timeout, func() {
 		err := c.Process.Kill()
 		if err != nil {
-			log.Printf("E! FATAL error killing process: %s", err)
+			log.Printf("E! [agent] Error killing process: %s", err)
 			return
 		}
 	})
 
 	err := c.Wait()
-	isTimeout := timer.Stop()
+	if err == nil {
+		return nil
+	}
 
-	if err != nil {
+	if !timer.Stop() {
-		return err
-	} else if isTimeout == false {
 		return TimeoutErr
 	}
 

plugins/outputs/all/all.go

@@ -11,6 +11,7 @@ import (
 	_ "github.com/influxdata/telegraf/plugins/outputs/datadog"
 	_ "github.com/influxdata/telegraf/plugins/outputs/discard"
 	_ "github.com/influxdata/telegraf/plugins/outputs/elasticsearch"
+	_ "github.com/influxdata/telegraf/plugins/outputs/exec"
 	_ "github.com/influxdata/telegraf/plugins/outputs/file"
 	_ "github.com/influxdata/telegraf/plugins/outputs/graphite"
 	_ "github.com/influxdata/telegraf/plugins/outputs/graylog"

plugins/outputs/exec/README.md

@@ -0,0 +1,26 @@
+# Exec Output Plugin
+
+This plugin sends telegraf metrics to an external application over stdin.
+
+The command should be defined similar to docker's `exec` form:
+
+    ["executable", "param1", "param2"]
+
+On non-zero exit stderr will be logged at error level.
+
+### Configuration
+
+```toml
+[[outputs.exec]]
+  ## Command to injest metrics via stdin.
+  command = ["tee", "-a", "/dev/null"]
+
+  ## Timeout for command to complete.
+  # timeout = "5s"
+
+  ## Data format to output.
+  ## Each data format has its own unique set of configuration options, read
+  ## more about them here:
+  ## https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_OUTPUT.md
+  # data_format = "influx"
+```

plugins/outputs/exec/exec.go

@@ -0,0 +1,153 @@
+package exec
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"log"
+	"os/exec"
+	"time"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/internal"
+	"github.com/influxdata/telegraf/plugins/outputs"
+	"github.com/influxdata/telegraf/plugins/serializers"
+)
+
+const maxStderrBytes = 512
+
+// Exec defines the exec output plugin.
+type Exec struct {
+	Command []string          `toml:"command"`
+	Timeout internal.Duration `toml:"timeout"`
+
+	runner     Runner
+	serializer serializers.Serializer
+}
+
+var sampleConfig = `
+  ## Command to injest metrics via stdin.
+  command = ["tee", "-a", "/dev/null"]
+
+  ## Timeout for command to complete.
+  # timeout = "5s"
+
+  ## Data format to output.
+  ## Each data format has its own unique set of configuration options, read
+  ## more about them here:
+  ## https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_OUTPUT.md
+  # data_format = "influx"
+`
+
+// SetSerializer sets the serializer for the output.
+func (e *Exec) SetSerializer(serializer serializers.Serializer) {
+	e.serializer = serializer
+}
+
+// Connect satisfies the Ouput interface.
+func (e *Exec) Connect() error {
+	return nil
+}
+
+// Close satisfies the Ouput interface.
+func (e *Exec) Close() error {
+	return nil
+}
+
+// Description describes the plugin.
+func (e *Exec) Description() string {
+	return "Send metrics to command as input over stdin"
+}
+
+// SampleConfig returns a sample configuration.
+func (e *Exec) SampleConfig() string {
+	return sampleConfig
+}
+
+// Write writes the metrics to the configured command.
+func (e *Exec) Write(metrics []telegraf.Metric) error {
+	var buffer bytes.Buffer
+	for _, metric := range metrics {
+		value, err := e.serializer.Serialize(metric)
+		if err != nil {
+			return err
+		}
+		buffer.Write(value)
+	}
+
+	if buffer.Len() <= 0 {
+		return nil
+	}
+
+	return e.runner.Run(e.Timeout.Duration, e.Command, &buffer)
+}
+
+// Runner provides an interface for running exec.Cmd.
+type Runner interface {
+	Run(time.Duration, []string, io.Reader) error
+}
+
+// CommandRunner runs a command with the ability to kill the process before the timeout.
+type CommandRunner struct {
+	cmd *exec.Cmd
+}
+
+// Run runs the command.
+func (c *CommandRunner) Run(timeout time.Duration, command []string, buffer io.Reader) error {
+	cmd := exec.Command(command[0], command[1:]...)
+	cmd.Stdin = buffer
+	var stderr bytes.Buffer
+	cmd.Stderr = &stderr
+
+	err := internal.RunTimeout(cmd, timeout)
+	s := stderr
+
+	if err != nil {
+		if err == internal.TimeoutErr {
+			return fmt.Errorf("%q timed out and was killed", command)
+		}
+
+		if s.Len() > 0 {
+			log.Printf("E! [outputs.exec] Command error: %q", truncate(s))
+		}
+
+		if status, ok := internal.ExitStatus(err); ok {
+			return fmt.Errorf("%q exited %d with %s", command, status, err.Error())
+		}
+
+		return fmt.Errorf("%q failed with %s", command, err.Error())
+	}
+
+	c.cmd = cmd
+
+	return nil
+}
+
+func truncate(buf bytes.Buffer) string {
+	// Limit the number of bytes.
+	didTruncate := false
+	if buf.Len() > maxStderrBytes {
+		buf.Truncate(maxStderrBytes)
+		didTruncate = true
+	}
+	if i := bytes.IndexByte(buf.Bytes(), '\n'); i > 0 {
+		// Only show truncation if the newline wasn't the last character.
+		if i < buf.Len()-1 {
+			didTruncate = true
+		}
+		buf.Truncate(i)
+	}
+	if didTruncate {
+		buf.WriteString("...")
+	}
+	return buf.String()
+}
+
+func init() {
+	outputs.Add("exec", func() telegraf.Output {
+		return &Exec{
+			runner:  &CommandRunner{},
+			Timeout: internal.Duration{Duration: time.Second * 5},
+		}
+	})
+}

plugins/outputs/exec/exec_test.go

@@ -0,0 +1,105 @@
+package exec
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/internal"
+	"github.com/influxdata/telegraf/plugins/serializers"
+	"github.com/influxdata/telegraf/testutil"
+)
+
+func TestExec(t *testing.T) {
+	if testing.Short() {
+		t.Skip("Skipping test due to OS/executable dependencies")
+	}
+
+	tests := []struct {
+		name    string
+		command []string
+		err     bool
+		metrics []telegraf.Metric
+	}{
+		{
+			name:    "test success",
+			command: []string{"tee"},
+			err:     false,
+			metrics: testutil.MockMetrics(),
+		},
+		{
+			name:    "test doesn't accept stdin",
+			command: []string{"sleep", "5s"},
+			err:     true,
+			metrics: testutil.MockMetrics(),
+		},
+		{
+			name:    "test command not found",
+			command: []string{"/no/exist", "-h"},
+			err:     true,
+			metrics: testutil.MockMetrics(),
+		},
+		{
+			name:    "test no metrics output",
+			command: []string{"tee"},
+			err:     false,
+			metrics: []telegraf.Metric{},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			e := &Exec{
+				Command: tt.command,
+				Timeout: internal.Duration{Duration: time.Second},
+				runner:  &CommandRunner{},
+			}
+
+			s, _ := serializers.NewInfluxSerializer()
+			e.SetSerializer(s)
+
+			e.Connect()
+
+			require.Equal(t, tt.err, e.Write(tt.metrics) != nil)
+		})
+	}
+}
+
+func TestTruncate(t *testing.T) {
+	tests := []struct {
+		name string
+		buf  *bytes.Buffer
+		len  int
+	}{
+		{
+			name: "long out",
+			buf:  bytes.NewBufferString(strings.Repeat("a", maxStderrBytes+100)),
+			len:  maxStderrBytes + len("..."),
+		},
+		{
+			name: "multiline out",
+			buf:  bytes.NewBufferString("hola\ngato\n"),
+			len:  len("hola") + len("..."),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			s := truncate(*tt.buf)
+			require.Equal(t, tt.len, len(s))
+		})
+	}
+}
+
+func TestExecDocs(t *testing.T) {
+	e := &Exec{}
+	e.Description()
+	e.SampleConfig()
+	require.NoError(t, e.Close())
+
+	e = &Exec{runner: &CommandRunner{}}
+	require.NoError(t, e.Close())
+}