feat: improve the format of --debug logs

internal/trace/context.go

@@ -36,7 +36,7 @@ func NewLogger(ctx context.Context, debug bool) (context.Context, logrus.FieldLo
 	}
 
 	logger := logrus.New()
-	logger.SetFormatter(&logrus.TextFormatter{DisableQuote: true})
+	logger.SetFormatter(&TextFormatter{})
 	logger.SetLevel(logLevel)
 	entry := logger.WithContext(ctx)
 	return context.WithValue(ctx, loggerKey, entry), entry

internal/trace/text_formatter.go

@@ -0,0 +1,50 @@
+/*
+Copyright The ORAS Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package trace
+
+import (
+	"bytes"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/sirupsen/logrus"
+)
+
+// TextFormatter formats logs into text.
+type TextFormatter struct{}
+
+// logEntrySeperator is the separator between log entries.
+const logEntrySeperator = "\n\n" // two empty lines
+
+// Format renders a single log entry.
+func (f *TextFormatter) Format(entry *logrus.Entry) ([]byte, error) {
+	var buf bytes.Buffer
+
+	timestamp := entry.Time.Format(time.RFC3339Nano)
+	levelText := strings.ToUpper(entry.Level.String())
+	fmt.Fprintf(&buf, "[%s][%s]: %s\n", timestamp, levelText, entry.Message)
+	// print data fields
+	if len(entry.Data) > 0 {
+		buf.WriteString("[Data]:\n")
+		for k, v := range entry.Data {
+			fmt.Fprintf(&buf, "  %s=%v\n", k, v)
+		}
+	}
+
+	buf.WriteString(logEntrySeperator)
+	return buf.Bytes(), nil
+}

internal/trace/text_formatter_test.go

@@ -0,0 +1,99 @@
+/*
+Copyright The ORAS Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package trace
+
+import (
+	"reflect"
+	"testing"
+	"time"
+
+	"github.com/sirupsen/logrus"
+)
+
+func TestTextFormatter_Format(t *testing.T) {
+	tests := []struct {
+		name    string
+		f       *TextFormatter
+		entry   *logrus.Entry
+		want    []byte
+		wantErr bool
+	}{
+		{
+			name: "debug log entry",
+			f:    &TextFormatter{},
+			entry: &logrus.Entry{
+				Time:    time.Date(2024, time.December, 1, 23, 30, 1, 55, time.UTC),
+				Level:   logrus.DebugLevel,
+				Message: "test debug",
+				Data:    logrus.Fields{},
+			},
+			want:    []byte("[2024-12-01T23:30:01.000000055Z][DEBUG]: test debug\n\n\n"),
+			wantErr: false,
+		},
+		{
+			name: "info log entry",
+			f:    &TextFormatter{},
+			entry: &logrus.Entry{
+				Time:    time.Date(2024, time.December, 1, 23, 30, 1, 55, time.UTC),
+				Level:   logrus.InfoLevel,
+				Message: "test info",
+				Data:    logrus.Fields{},
+			},
+			want:    []byte("[2024-12-01T23:30:01.000000055Z][INFO]: test info\n\n\n"),
+			wantErr: false,
+		},
+		{
+			name: "warning log entry with data fields",
+			f:    &TextFormatter{},
+			entry: &logrus.Entry{
+				Time:    time.Date(2024, time.December, 1, 23, 30, 1, 55, time.UTC),
+				Level:   logrus.WarnLevel,
+				Message: "test warning with fields",
+				Data: logrus.Fields{
+					"testkey": "testval",
+				},
+			},
+			want:    []byte("[2024-12-01T23:30:01.000000055Z][WARNING]: test warning with fields\n[Data]:\n  testkey=testval\n\n\n"),
+			wantErr: false,
+		},
+		{
+			name: "error log entry with data fields",
+			f:    &TextFormatter{},
+			entry: &logrus.Entry{
+				Time:    time.Date(2024, time.December, 1, 23, 30, 1, 55, time.UTC),
+				Level:   logrus.ErrorLevel,
+				Message: "test warning with fields",
+				Data: logrus.Fields{
+					"testkey": 123,
+				},
+			},
+			want:    []byte("[2024-12-01T23:30:01.000000055Z][ERROR]: test warning with fields\n[Data]:\n  testkey=123\n\n\n"),
+			wantErr: false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := tt.f.Format(tt.entry)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("TextFormatter.Format() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("TextFormatter.Format() = %s, want %s", got, tt.want)
+			}
+		})
+	}
+}

internal/trace/transport.go

@@ -16,7 +16,10 @@ limitations under the License.
 package trace
 
 import (
+	"bytes"
 	"fmt"
+	"io"
+	"mime"
 	"net/http"
 	"strings"
 	"sync/atomic"
@@ -34,6 +37,9 @@ var (
 	}
 )
 
+// payloadSizeLimit limits the maximum size of the response body to be printed.
+const payloadSizeLimit int64 = 4 * 1024 // 4 KiB
+
 // Transport is an http.RoundTripper that keeps track of the in-flight
 // request and add hooks to report HTTP tracing events.
 type Transport struct {
@@ -54,7 +60,7 @@ func (t *Transport) RoundTrip(req *http.Request) (resp *http.Response, err error
 	e := Logger(ctx)
 
 	// log the request
-	e.Debugf("Request #%d\n> Request URL: %q\n> Request method: %q\n> Request headers:\n%s",
+	e.Debugf("--> Request #%d\n> Request URL: %q\n> Request method: %q\n> Request headers:\n%s",
 		id, req.URL, req.Method, logHeader(req.Header))
 
 	// log the response
@@ -64,8 +70,8 @@ func (t *Transport) RoundTrip(req *http.Request) (resp *http.Response, err error
 	} else if resp == nil {
 		e.Errorf("No response obtained for request %s %q", req.Method, req.URL)
 	} else {
-		e.Debugf("Response #%d\n< Response Status: %q\n< Response headers:\n%s",
-			id, resp.Status, logHeader(resp.Header))
+		e.Debugf("<-- Response #%d\n< Response Status: %q\n< Response headers:\n%s\n< Response body:\n%s",
+			id, resp.Status, logHeader(resp.Header), logResponseBody(resp))
 	}
 	return resp, err
 }
@@ -87,3 +93,59 @@ func logHeader(header http.Header) string {
 	}
 	return "   Empty header"
 }
+
+// logResponseBody prints out the response body if it is printable and within
+// the size limit.
+func logResponseBody(resp *http.Response) string {
+	if resp.Body == nil || resp.Body == http.NoBody {
+		return "   No response body to print"
+	}
+
+	// non-applicable body is not printed and remains untouched for subsequent processing
+	contentType := resp.Header.Get("Content-Type")
+	if !isPrintableContentType(contentType) {
+		return fmt.Sprintf("   Response body of content type \"%s\" is not printed", contentType)
+	}
+
+	buf := bytes.NewBuffer(nil)
+	body := resp.Body
+	// restore the body by concatenating the read body with the remaining body
+	resp.Body = struct {
+		io.Reader
+		io.Closer
+	}{
+		Reader: io.MultiReader(buf, body),
+		Closer: body,
+	}
+	// read the body up to limit+1 to check if the body exceeds the limit
+	if _, err := io.CopyN(buf, body, payloadSizeLimit+1); err != nil && err != io.EOF {
+		return fmt.Sprintf("   Error reading response body: %v", err)
+	}
+
+	readBody := buf.Bytes()
+	if len(readBody) == 0 {
+		return "   Response body is empty"
+	}
+	if len(readBody) > int(payloadSizeLimit) {
+		return string(readBody[:payloadSizeLimit]) + "\n...(truncated)"
+	}
+	return string(readBody)
+}
+
+// isPrintableContentType returns true if the content of contentType is printable.
+func isPrintableContentType(contentType string) bool {
+	mediaType, _, err := mime.ParseMediaType(contentType)
+	if err != nil {
+		return false
+	}
+
+	if mediaType == "application/json" || strings.HasSuffix(mediaType, "+json") {
+		// JSON types
+		return true
+	}
+	if mediaType == "text/plain" {
+		// text types
+		return true
+	}
+	return false
+}