Monitor file download.

pkg/nullio/content_length.go

@@ -3,7 +3,10 @@ package nullio
 import (
 	"errors"
 	"fmt"
+	"github.com/influxdata/influxdb-client-go/v2/api/write"
+	"github.com/openHPI/poseidon/pkg/monitoring"
 	"net/http"
+	"strconv"
 )
 
 var ErrRegexMatching = errors.New("could not match content length")
@@ -12,20 +15,31 @@ var ErrRegexMatching = errors.New("could not match content length")
 // It parses the size from the first line as Content Length Header and streams the following data to the Target.
 // The first line is expected to follow the format headerLineRegex.
 type ContentLengthWriter struct {
-	Target           http.ResponseWriter
-	contentLengthSet bool
-	firstLine        []byte
+	Target                http.ResponseWriter
+	contentLengthSet      bool
+	firstLine             []byte
+	expectedContentLength int
+	actualContentLength   int
 }
 
 func (w *ContentLengthWriter) Write(p []byte) (count int, err error) {
 	if w.contentLengthSet {
-		count, err = w.Target.Write(p)
-		if err != nil {
-			err = fmt.Errorf("could not write to target: %w", err)
-		}
-		return count, err
+		return w.handleDataForwarding(p)
+	} else {
+		return w.handleContentLengthParsing(p)
 	}
+}
 
+func (w *ContentLengthWriter) handleDataForwarding(p []byte) (int, error) {
+	count, err := w.Target.Write(p)
+	if err != nil {
+		err = fmt.Errorf("could not write to target: %w", err)
+	}
+	w.actualContentLength += count
+	return count, err
+}
+
+func (w *ContentLengthWriter) handleContentLengthParsing(p []byte) (count int, err error) {
 	for i, char := range p {
 		if char != '\n' {
 			continue
@@ -38,6 +52,10 @@ func (w *ContentLengthWriter) Write(p []byte) (count int, err error) {
 			return 0, ErrRegexMatching
 		}
 		size := string(matches[headerLineGroupSize])
+		w.expectedContentLength, err = strconv.Atoi(size)
+		if err != nil {
+			log.WithField("size", size).Warn("could not parse content length")
+		}
 		w.Target.Header().Set("Content-Length", size)
 		w.contentLengthSet = true
 
@@ -57,3 +75,10 @@ func (w *ContentLengthWriter) Write(p []byte) (count int, err error) {
 
 	return len(p), nil
 }
+
+// SendMonitoringData will send a monitoring event of the content length read and written.
+func (w *ContentLengthWriter) SendMonitoringData(p *write.Point) {
+	p.AddField(monitoring.InfluxKeyExpectedContentLength, w.expectedContentLength)
+	p.AddField(monitoring.InfluxKeyActualContentLength, w.actualContentLength)
+	monitoring.WriteInfluxPoint(p)
+}