added poseidon with aws to k8s changes

pkg/nullio/content_length.go

@@ -0,0 +1,84 @@
+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")
+
+// ContentLengthWriter implements io.Writer.
+// 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
+	expectedContentLength int
+	actualContentLength   int
+}
+
+func (w *ContentLengthWriter) Write(p []byte) (count int, err error) {
+	if w.contentLengthSet {
+		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
+		}
+
+		w.firstLine = append(w.firstLine, p[:i]...)
+		matches := headerLineRegex.FindSubmatch(w.firstLine)
+		if len(matches) < headerLineGroupName {
+			log.WithField("line", string(w.firstLine)).Error(ErrRegexMatching.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
+
+		if i < len(p)-1 {
+			count, err = w.Target.Write(p[i+1:])
+			if err != nil {
+				err = fmt.Errorf("could not write to target: %w", err)
+			}
+		}
+
+		return len(p[:i]) + 1 + count, err
+	}
+
+	if !w.contentLengthSet {
+		w.firstLine = append(w.firstLine, p...)
+	}
+
+	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)
+}