influx fix

exporters/influxdb.go

@@ -4,8 +4,11 @@ import (
 	"bytes"
 	"context"
 	"fmt"
+	"io"
+	"math"
 	"net/http"
 	"sort"
+	"strconv"
 	"strings"
 	"time"
 
@@ -65,9 +68,8 @@ func (e *InfluxDBExporter) Write(ctx context.Context, metrics []core.Metric) err
 	defer resp.Body.Close()
 
 	if resp.StatusCode >= 300 {
-		buf := make([]byte, 256)
-		n, _ := resp.Body.Read(buf)
-		return fmt.Errorf("influxdb: HTTP %d: %s", resp.StatusCode, string(buf[:n]))
+		msg, _ := io.ReadAll(io.LimitReader(resp.Body, 512))
+		return fmt.Errorf("influxdb: HTTP %d: %s", resp.StatusCode, string(msg))
 	}
 
 	return nil
@@ -80,23 +82,22 @@ func (e *InfluxDBExporter) Write(ctx context.Context, metrics []core.Metric) err
 // Each metric becomes one line:
 //
 //	measurement,tag1=val1,tag2=val2 value=<float> <timestamp_ns>
+//
+// Values are always written as floats. InfluxDB fixes the type of a column
+// at the first write, so a value that flips between integer and float
+// syntax would be rejected later. NaN and Inf have no line protocol form
+// and are skipped, as are empty tag values.
 func EncodeLineProtocol(metrics []core.Metric) string {
-	if len(metrics) == 0 {
-		return ""
-	}
+	lines := make([]string, 0, len(metrics))
 
-	var b strings.Builder
-	b.Grow(len(metrics) * 128)
-
-	for i, m := range metrics {
-		if i > 0 {
-			b.WriteByte('\n')
+	for _, m := range metrics {
+		if m.Name == "" || math.IsNaN(m.Value) || math.IsInf(m.Value, 0) {
+			continue
 		}
 
-		// Measurement
+		var b strings.Builder
 		b.WriteString(escapeMeasurement(m.Name))
 
-		// Tags (sorted for determinism)
 		if len(m.Labels) > 0 {
 			keys := make([]string, 0, len(m.Labels))
 			for k := range m.Labels {
@@ -105,62 +106,42 @@ func EncodeLineProtocol(metrics []core.Metric) string {
 			sort.Strings(keys)
 
 			for _, k := range keys {
+				v := m.Labels[k]
+				if k == "" || v == "" {
+					continue
+				}
 				b.WriteByte(',')
-				b.WriteString(escapeTagKey(k))
+				b.WriteString(escapeTag(k))
 				b.WriteByte('=')
-				b.WriteString(escapeTagValue(m.Labels[k]))
+				b.WriteString(escapeTag(v))
 			}
 		}
 
-		// Fields
 		b.WriteString(" value=")
 		b.WriteString(formatFloat(m.Value))
 
-		// Timestamp (nanoseconds since epoch)
 		if !m.Timestamp.IsZero() {
 			b.WriteByte(' ')
-			fmt.Fprintf(&b, "%d", m.Timestamp.UnixNano())
+			b.WriteString(strconv.FormatInt(m.Timestamp.UnixNano(), 10))
 		}
+
+		lines = append(lines, b.String())
 	}
 
-	return b.String()
+	return strings.Join(lines, "\n")
 }
 
-func escapeMeasurement(s string) string {
-	if strings.ContainsAny(s, ", ") {
-		var b strings.Builder
-		for _, c := range s {
-			if c == ',' || c == ' ' {
-				b.WriteByte('\\')
-			}
-			b.WriteRune(c)
-		}
-		return b.String()
-	}
-	return s
-}
+var (
+	measurementEscaper = strings.NewReplacer(",", `\,`, " ", `\ `)
+	tagEscaper         = strings.NewReplacer(",", `\,`, "=", `\=`, " ", `\ `)
+)
 
-func escapeTagKey(s string) string {
-	return escapeTagValue(s)
-}
+func escapeMeasurement(s string) string { return measurementEscaper.Replace(s) }
 
-func escapeTagValue(s string) string {
-	if strings.ContainsAny(s, ", =") {
-		var b strings.Builder
-		for _, c := range s {
-			if c == ',' || c == '=' || c == ' ' {
-				b.WriteByte('\\')
-			}
-			b.WriteRune(c)
-		}
-		return b.String()
-	}
-	return s
-}
+func escapeTag(s string) string { return tagEscaper.Replace(s) }
 
+// formatFloat renders a float in line protocol float syntax. A value such
+// as 100 is written as "100", which InfluxDB reads as a float.
 func formatFloat(f float64) string {
-	if f == float64(int64(f)) && f < 9.223372036854775807e18 && f > -9.223372036854775808e18 {
-		return fmt.Sprintf("%di", int64(f))
-	}
-	return fmt.Sprintf("%g", f)
+	return strconv.FormatFloat(f, 'f', -1, 64)
 }

main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"context"
+	"flag"
 	"log"
 	"os/signal"
 	"syscall"
@@ -14,7 +15,10 @@ import (
 )
 
 func main() {
-	cfg, err := config.Load("config/config.yaml")
+	cfgPath := flag.String("config", "config/config.yaml", "path to the YAML config file")
+	flag.Parse()
+
+	cfg, err := config.Load(*cfgPath)
 	if err != nil {
 		log.Fatalf("config: %v", err)
 	}