Add logfmt parser (influxdata#4539)

docs/DATA_FORMATS_INPUT.md

@@ -10,6 +10,7 @@ Telegraf is able to parse the following input data formats into metrics:
 1. [Collectd](#collectd)
 1. [Dropwizard](#dropwizard)
 1. [Grok](#grok)
+1. [Logfmt](#logfmt)
 1. [Wavefront](#wavefront)
 
 Telegraf metrics, like InfluxDB
@@ -882,6 +883,22 @@ the file output will only print once per `flush_interval`.
 - If successful, add the next token, update the pattern and retest.
 - Continue one token at a time until the entire line is successfully parsed.
 
+# Logfmt
+This parser implements the logfmt format by extracting and converting key-value pairs from log text in the form `<key>=<value>`.
+At the moment, the plugin will produce one metric per line and all keys
+are added as fields.
+A typical log
+```
+method=GET host=influxdata.org ts=2018-07-24T19:43:40.275Z
+connect=4ms service=8ms status=200 bytes=1653
+```
+will be converted into
+```
+logfmt method="GET",host="influxdata.org",ts="2018-07-24T19:43:40.275Z",connect="4ms",service="8ms",status=200i,bytes=1653i
+
+```
+Additional information about the logfmt format can be found [here](https://brandur.org/logfmt).
+
 # Wavefront:
 
 Wavefront Data Format is metrics are parsed directly into Telegraf metrics.

plugins/parsers/logfmt/parser.go

@@ -0,0 +1,111 @@
+package logfmt
+
+import (
+	"bytes"
+	"fmt"
+	"strconv"
+	"time"
+
+	"github.com/go-logfmt/logfmt"
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/metric"
+)
+
+var (
+	ErrNoMetric = fmt.Errorf("no metric in line")
+)
+
+// Parser decodes logfmt formatted messages into metrics.
+type Parser struct {
+	MetricName  string
+	DefaultTags map[string]string
+	Now         func() time.Time
+}
+
+// NewParser creates a parser.
+func NewParser(metricName string, defaultTags map[string]string) *Parser {
+	return &Parser{
+		MetricName:  metricName,
+		DefaultTags: defaultTags,
+		Now:         time.Now,
+	}
+}
+
+// Parse converts a slice of bytes in logfmt format to metrics.
+func (p *Parser) Parse(b []byte) ([]telegraf.Metric, error) {
+	reader := bytes.NewReader(b)
+	decoder := logfmt.NewDecoder(reader)
+	metrics := make([]telegraf.Metric, 0)
+	for {
+		ok := decoder.ScanRecord()
+		if !ok {
+			err := decoder.Err()
+			if err != nil {
+				return nil, err
+			}
+			break
+		}
+		fields := make(map[string]interface{})
+		for decoder.ScanKeyval() {
+			if string(decoder.Value()) == "" {
+				continue
+			}
+
+			//type conversions
+			value := string(decoder.Value())
+			if iValue, err := strconv.ParseInt(value, 10, 64); err == nil {
+				fields[string(decoder.Key())] = iValue
+			} else if fValue, err := strconv.ParseFloat(value, 64); err == nil {
+				fields[string(decoder.Key())] = fValue
+			} else if bValue, err := strconv.ParseBool(value); err == nil {
+				fields[string(decoder.Key())] = bValue
+			} else {
+				fields[string(decoder.Key())] = value
+			}
+		}
+		if len(fields) == 0 {
+			continue
+		}
+
+		m, err := metric.New(p.MetricName, map[string]string{}, fields, p.Now())
+		if err != nil {
+			return nil, err
+		}
+
+		metrics = append(metrics, m)
+	}
+	p.applyDefaultTags(metrics)
+	return metrics, nil
+}
+
+// ParseLine converts a single line of text in logfmt format to metrics.
+func (p *Parser) ParseLine(s string) (telegraf.Metric, error) {
+	metrics, err := p.Parse([]byte(s))
+	if err != nil {
+		return nil, err
+	}
+
+	if len(metrics) < 1 {
+		return nil, ErrNoMetric
+	}
+	return metrics[0], nil
+}
+
+// SetDefaultTags adds tags to the metrics outputs of Parse and ParseLine.
+func (p *Parser) SetDefaultTags(tags map[string]string) {
+	p.DefaultTags = tags
+}
+
+func (p *Parser) applyDefaultTags(metrics []telegraf.Metric) {
+	if len(p.DefaultTags) == 0 {
+		return
+	}
+
+	for _, m := range metrics {
+		for k, v := range p.DefaultTags {
+			if !m.HasTag(k) {
+				m.AddTag(k, v)
+			}
+		}
+	}
+}

plugins/parsers/logfmt/parser_test.go

@@ -0,0 +1,231 @@
+package logfmt
+
+import (
+	"testing"
+	"time"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/metric"
+	"github.com/influxdata/telegraf/testutil"
+	"github.com/stretchr/testify/require"
+)
+
+func MustMetric(t *testing.T, m *testutil.Metric) telegraf.Metric {
+	t.Helper()
+	v, err := metric.New(m.Measurement, m.Tags, m.Fields, m.Time)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return v
+}
+
+func TestParse(t *testing.T) {
+	tests := []struct {
+		name        string
+		measurement string
+		now         func() time.Time
+		bytes       []byte
+		want        []testutil.Metric
+		wantErr     bool
+	}{
+		{
+			name: "no bytes returns no metrics",
+			now:  func() time.Time { return time.Unix(0, 0) },
+			want: []testutil.Metric{},
+		},
+		{
+			name:        "test without trailing end",
+			bytes:       []byte("foo=\"bar\""),
+			now:         func() time.Time { return time.Unix(0, 0) },
+			measurement: "testlog",
+			want: []testutil.Metric{
+				testutil.Metric{
+					Measurement: "testlog",
+					Tags:        map[string]string{},
+					Fields: map[string]interface{}{
+						"foo": "bar",
+					},
+					Time: time.Unix(0, 0),
+				},
+			},
+		},
+		{
+			name:        "test with trailing end",
+			bytes:       []byte("foo=\"bar\"\n"),
+			now:         func() time.Time { return time.Unix(0, 0) },
+			measurement: "testlog",
+			want: []testutil.Metric{
+				testutil.Metric{
+					Measurement: "testlog",
+					Tags:        map[string]string{},
+					Fields: map[string]interface{}{
+						"foo": "bar",
+					},
+					Time: time.Unix(0, 0),
+				},
+			},
+		},
+		{
+			name:        "logfmt parser returns all the fields",
+			bytes:       []byte(`ts=2018-07-24T19:43:40.275Z lvl=info msg="http request" method=POST`),
+			now:         func() time.Time { return time.Unix(0, 0) },
+			measurement: "testlog",
+			want: []testutil.Metric{
+				testutil.Metric{
+					Measurement: "testlog",
+					Tags:        map[string]string{},
+					Fields: map[string]interface{}{
+						"lvl":    "info",
+						"msg":    "http request",
+						"method": "POST",
+						"ts":     "2018-07-24T19:43:40.275Z",
+					},
+					Time: time.Unix(0, 0),
+				},
+			},
+		},
+		{
+			name:        "logfmt parser parses every line",
+			bytes:       []byte("ts=2018-07-24T19:43:40.275Z lvl=info msg=\"http request\" method=POST\nparent_id=088876RL000 duration=7.45 log_id=09R4e4Rl000"),
+			now:         func() time.Time { return time.Unix(0, 0) },
+			measurement: "testlog",
+			want: []testutil.Metric{
+				testutil.Metric{
+					Measurement: "testlog",
+					Tags:        map[string]string{},
+					Fields: map[string]interface{}{
+						"lvl":    "info",
+						"msg":    "http request",
+						"method": "POST",
+						"ts":     "2018-07-24T19:43:40.275Z",
+					},
+					Time: time.Unix(0, 0),
+				},
+				testutil.Metric{
+					Measurement: "testlog",
+					Tags:        map[string]string{},
+					Fields: map[string]interface{}{
+						"parent_id": "088876RL000",
+						"duration":  7.45,
+						"log_id":    "09R4e4Rl000",
+					},
+					Time: time.Unix(0, 0),
+				},
+			},
+		},
+		{
+			name:    "keys without = or values are ignored",
+			now:     func() time.Time { return time.Unix(0, 0) },
+			bytes:   []byte(`i am no data.`),
+			want:    []testutil.Metric{},
+			wantErr: false,
+		},
+		{
+			name:    "keys without values are ignored",
+			now:     func() time.Time { return time.Unix(0, 0) },
+			bytes:   []byte(`foo="" bar=`),
+			want:    []testutil.Metric{},
+			wantErr: false,
+		},
+		{
+			name:        "unterminated quote produces error",
+			now:         func() time.Time { return time.Unix(0, 0) },
+			measurement: "testlog",
+			bytes:       []byte(`bar=baz foo="bar`),
+			want:        []testutil.Metric{},
+			wantErr:     true,
+		},
+		{
+			name:        "malformed key",
+			now:         func() time.Time { return time.Unix(0, 0) },
+			measurement: "testlog",
+			bytes:       []byte(`"foo=" bar=baz`),
+			want:        []testutil.Metric{},
+			wantErr:     true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			l := Parser{
+				MetricName: tt.measurement,
+				Now:        tt.now,
+			}
+			got, err := l.Parse(tt.bytes)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("Logfmt.Parse error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			require.Equal(t, len(tt.want), len(got))
+			for i, m := range got {
+				testutil.MustEqual(t, m, tt.want[i])
+			}
+		})
+	}
+}
+
+func TestParseLine(t *testing.T) {
+	tests := []struct {
+		name        string
+		s           string
+		measurement string
+		now         func() time.Time
+		want        testutil.Metric
+		wantErr     bool
+	}{
+		{
+			name:    "No Metric In line",
+			now:     func() time.Time { return time.Unix(0, 0) },
+			want:    testutil.Metric{},
+			wantErr: true,
+		},
+		{
+			name:        "Log parser fmt returns all fields",
+			now:         func() time.Time { return time.Unix(0, 0) },
+			measurement: "testlog",
+			s:           `ts=2018-07-24T19:43:35.207268Z lvl=5 msg="Write failed" log_id=09R4e4Rl000`,
+			want: testutil.Metric{
+				Measurement: "testlog",
+				Fields: map[string]interface{}{
+					"ts":     "2018-07-24T19:43:35.207268Z",
+					"lvl":    int64(5),
+					"msg":    "Write failed",
+					"log_id": "09R4e4Rl000",
+				},
+				Tags: map[string]string{},
+				Time: time.Unix(0, 0),
+			},
+		},
+		{
+			name:        "ParseLine only returns metrics from first string",
+			now:         func() time.Time { return time.Unix(0, 0) },
+			measurement: "testlog",
+			s:           "ts=2018-07-24T19:43:35.207268Z lvl=5 msg=\"Write failed\" log_id=09R4e4Rl000\nmethod=POST parent_id=088876RL000 duration=7.45 log_id=09R4e4Rl000",
+			want: testutil.Metric{
+				Measurement: "testlog",
+				Fields: map[string]interface{}{
+					"ts":     "2018-07-24T19:43:35.207268Z",
+					"lvl":    int64(5),
+					"msg":    "Write failed",
+					"log_id": "09R4e4Rl000",
+				},
+				Tags: map[string]string{},
+				Time: time.Unix(0, 0),
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			l := Parser{
+				MetricName: tt.measurement,
+				Now:        tt.now,
+			}
+			got, err := l.ParseLine(tt.s)
+			if (err != nil) != tt.wantErr {
+				t.Fatalf("Logfmt.Parse error = %v, wantErr %v", err, tt.wantErr)
+			}
+			if got != nil {
+				testutil.MustEqual(t, got, tt.want)
+			}
+		})
+	}
+}