Replace non-utf8 characters in bodies

sdk/instrumentation/bodyattribute/bodyattribute.go

@@ -3,6 +3,7 @@ package bodyattribute // import "github.com/hypertrace/goagent/sdk/instrumentati
 import (
 	"encoding/base64"
 	"fmt"
+	"unicode/utf8"
 
 	"github.com/hypertrace/goagent/sdk"
 )
@@ -21,7 +22,9 @@ func SetTruncatedBodyAttribute(attrName string, body []byte, bodyMaxSize int, sp
 		return
 	}
 
-	SetBodyAttribute(attrName, body[:bodyMaxSize], true, span)
+	truncatedBody := truncateUTF8Bytes(body, bodyMaxSize)
+
+	SetBodyAttribute(attrName, truncatedBody, true, span)
 }
 
 // SetTruncatedEncodedBodyAttribute is like SetTruncatedBodyAttribute above but also base64 encodes the
@@ -38,7 +41,8 @@ func SetTruncatedEncodedBodyAttribute(attrName string, body []byte, bodyMaxSize
 		return
 	}
 
-	SetEncodedBodyAttribute(attrName, body[:bodyMaxSize], true, span)
+	truncatedBody := truncateUTF8Bytes(body, bodyMaxSize)
+	SetEncodedBodyAttribute(attrName, truncatedBody, true, span)
 }
 
 // SetBodyAttribute sets the body as a span attribute.
@@ -69,3 +73,24 @@ func SetEncodedBodyAttribute(attrName string, body []byte, truncated bool, span
 		span.SetAttribute(fmt.Sprintf("%s.truncated", attrName), true)
 	}
 }
+
+// Largely based on:
+// https://github.com/jmacd/opentelemetry-go/blob/e8973b75b230246545cdae072a548c83877cba09/sdk/trace/span.go#L358-L375
+func truncateUTF8Bytes(b []byte, maxBytes int) []byte {
+	// We subtract 4 as that is the largest possible byte size for single rune
+	startIndex := maxBytes - 4
+	if startIndex < 0 {
+		startIndex = 0
+	}
+
+	for idx := startIndex; idx < maxBytes; {
+		_, size := utf8.DecodeRune(b[idx:])
+		if idx+size > maxBytes {
+			// We're past maxBytes with this rune, we will not include this in truncated value
+			return b[:idx]
+		}
+		idx += size
+	}
+
+	return b[:maxBytes]
+}

sdk/instrumentation/bodyattribute/bodyattribute_test.go

@@ -199,3 +199,25 @@ func TestSetEncodedBodyAttribute(t *testing.T) {
 		})
 	}
 }
+
+func TestSetBodyWithoutUtf8(t *testing.T) {
+	multiByteCharString := []byte("こんにちは世界こんにちは世界こんにちは世界こんにちは世界こんにちは世界")
+	span := mock.NewSpan()
+	SetTruncatedBodyAttribute("http.request.body", multiByteCharString, 23, span)
+	value := span.ReadAttribute("http.request.body")
+	assert.Equal(t, value.(string), "こんにちは世界")
+	v := len(value.(string))
+	assert.Equal(t, v, 21)
+}
+
+func TestSetB64BodyWithoutUtf8(t *testing.T) {
+	multiByteCharString := []byte("こんにちは世界こんにちは世界こんにちは世界こんにちは世界こんにちは世界")
+	span := mock.NewSpan()
+	SetTruncatedEncodedBodyAttribute("http.request.body", multiByteCharString, 23, span)
+	value := span.ReadAttribute("http.request.body.base64")
+	decodedBytes, err := base64.StdEncoding.DecodeString(value.(string))
+	assert.NoError(t, err)
+	assert.Equal(t, string(decodedBytes), "こんにちは世界")
+	v := len(decodedBytes)
+	assert.Equal(t, v, 21)
+}