Fix race condition in the Wavefront parser (influxdata#5764)

Author: prydin

plugins/parsers/wavefront/parser.go

@@ -6,6 +6,7 @@ import (
 	"io"
 	"log"
 	"strconv"
+	"sync"
 	"time"
 
 	"github.com/influxdata/telegraf"
@@ -22,18 +23,23 @@ type Point struct {
 	Tags      map[string]string
 }
 
-// Parser represents a parser.
+type WavefrontParser struct {
+	parsers     *sync.Pool
+	defaultTags map[string]string
+}
+
+// PointParser is a thread-unsafe parser and must be kept in a pool.
 type PointParser struct {
 	s   *PointScanner
 	buf struct {
 		tok []Token  // last read n tokens
 		lit []string // last read n literals
 		n   int      // unscanned buffer size (max=2)
 	}
-	scanBuf     bytes.Buffer // buffer reused for scanning tokens
-	writeBuf    bytes.Buffer // buffer reused for parsing elements
-	Elements    []ElementParser
-	defaultTags map[string]string
+	scanBuf  bytes.Buffer // buffer reused for scanning tokens
+	writeBuf bytes.Buffer // buffer reused for parsing elements
+	Elements []ElementParser
+	parent   *WavefrontParser
 }
 
 // Returns a slice of ElementParser's for the Graphite format
@@ -47,9 +53,40 @@ func NewWavefrontElements() []ElementParser {
 	return elements
 }
 
-func NewWavefrontParser(defaultTags map[string]string) *PointParser {
+func NewWavefrontParser(defaultTags map[string]string) *WavefrontParser {
+	wp := &WavefrontParser{defaultTags: defaultTags}
+	wp.parsers = &sync.Pool{
+		New: func() interface{} {
+			return NewPointParser(wp)
+		},
+	}
+	return wp
+}
+
+func NewPointParser(parent *WavefrontParser) *PointParser {
 	elements := NewWavefrontElements()
-	return &PointParser{Elements: elements, defaultTags: defaultTags}
+	return &PointParser{Elements: elements, parent: parent}
+}
+
+func (p *WavefrontParser) ParseLine(line string) (telegraf.Metric, error) {
+	buf := []byte(line)
+
+	metrics, err := p.Parse(buf)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(metrics) > 0 {
+		return metrics[0], nil
+	}
+
+	return nil, nil
+}
+
+func (p *WavefrontParser) Parse(buf []byte) ([]telegraf.Metric, error) {
+	pp := p.parsers.Get().(*PointParser)
+	defer p.parsers.Put(pp)
+	return pp.Parse(buf)
 }
 
 func (p *PointParser) Parse(buf []byte) ([]telegraf.Metric, error) {
@@ -91,21 +128,7 @@ func (p *PointParser) Parse(buf []byte) ([]telegraf.Metric, error) {
 	return metrics, nil
 }
 
-func (p *PointParser) ParseLine(line string) (telegraf.Metric, error) {
-	buf := []byte(line)
-	metrics, err := p.Parse(buf)
-	if err != nil {
-		return nil, err
-	}
-
-	if len(metrics) > 0 {
-		return metrics[0], nil
-	}
-
-	return nil, nil
-}
-
-func (p *PointParser) SetDefaultTags(tags map[string]string) {
+func (p *WavefrontParser) SetDefaultTags(tags map[string]string) {
 	p.defaultTags = tags
 }
 
@@ -119,7 +142,7 @@ func (p *PointParser) convertPointToTelegrafMetric(points []Point) ([]telegraf.M
 			tags[k] = v
 		}
 		// apply default tags after parsed tags
-		for k, v := range p.defaultTags {
+		for k, v := range p.parent.defaultTags {
 			tags[k] = v
 		}