Ensure proper logs for aborted streaming responses

pkg/middlewares/accesslog/logger.go

@@ -196,16 +196,6 @@ func (h *Handler) ServeHTTP(rw http.ResponseWriter, req *http.Request, next http
 		},
 	}
 
-	defer func() {
-		if h.config.BufferingSize > 0 {
-			h.logHandlerChan <- handlerParams{
-				logDataTable: logDataTable,
-			}
-			return
-		}
-		h.logTheRoundTrip(logDataTable)
-	}()
-
 	reqWithDataTable := req.WithContext(context.WithValue(req.Context(), DataTableKey, logDataTable))
 
 	core[RequestCount] = nextRequestCount()
@@ -249,12 +239,7 @@ func (h *Handler) ServeHTTP(rw http.ResponseWriter, req *http.Request, next http
 		return
 	}
 
-	next.ServeHTTP(rw, reqWithDataTable)
-
-	if _, ok := core[ClientUsername]; !ok {
-		core[ClientUsername] = usernameIfPresent(reqWithDataTable.URL)
-	}
-
+	defer func() {
 		logDataTable.DownstreamResponse = downstreamResponse{
 			headers: rw.Header().Clone(),
 		}
@@ -262,6 +247,22 @@ func (h *Handler) ServeHTTP(rw http.ResponseWriter, req *http.Request, next http
 		logDataTable.DownstreamResponse.status = capt.StatusCode()
 		logDataTable.DownstreamResponse.size = capt.ResponseSize()
 		logDataTable.Request.size = capt.RequestSize()
+
+		if _, ok := core[ClientUsername]; !ok {
+			core[ClientUsername] = usernameIfPresent(reqWithDataTable.URL)
+		}
+
+		if h.config.BufferingSize > 0 {
+			h.logHandlerChan <- handlerParams{
+				logDataTable: logDataTable,
+			}
+			return
+		}
+
+		h.logTheRoundTrip(logDataTable)
+	}()
+
+	next.ServeHTTP(rw, reqWithDataTable)
 }
 
 // Close closes the Logger (i.e. the file, drain logHandlerChan, etc).

pkg/middlewares/accesslog/logger_test.go

@@ -2,6 +2,7 @@ package accesslog
 
 import (
 	"bytes"
+	"context"
 	"crypto/tls"
 	"encoding/json"
 	"fmt"
@@ -22,6 +23,7 @@ import (
 	"github.com/stretchr/testify/require"
 	ptypes "github.com/traefik/paerser/types"
 	"github.com/traefik/traefik/v2/pkg/middlewares/capture"
+	"github.com/traefik/traefik/v2/pkg/middlewares/recovery"
 	"github.com/traefik/traefik/v2/pkg/types"
 )
 
@@ -519,6 +521,64 @@ func TestLoggerJSON(t *testing.T) {
 	}
 }
 
+func TestLogger_AbortedRequest(t *testing.T) {
+	expected := map[string]func(t *testing.T, value interface{}){
+		RequestContentSize:             assertFloat64(0),
+		RequestHost:                    assertString(testHostname),
+		RequestAddr:                    assertString(testHostname),
+		RequestMethod:                  assertString(testMethod),
+		RequestPath:                    assertString(""),
+		RequestProtocol:                assertString(testProto),
+		RequestScheme:                  assertString(testScheme),
+		RequestPort:                    assertString("-"),
+		DownstreamStatus:               assertFloat64(float64(200)),
+		DownstreamContentSize:          assertFloat64(float64(40)),
+		RequestRefererHeader:           assertString(testReferer),
+		RequestUserAgentHeader:         assertString(testUserAgent),
+		ServiceURL:                     assertString("http://stream"),
+		ServiceAddr:                    assertString("127.0.0.1"),
+		ServiceName:                    assertString("stream"),
+		ClientUsername:                 assertString(testUsername),
+		ClientHost:                     assertString(testHostname),
+		ClientPort:                     assertString(strconv.Itoa(testPort)),
+		ClientAddr:                     assertString(fmt.Sprintf("%s:%d", testHostname, testPort)),
+		"level":                        assertString("info"),
+		"msg":                          assertString(""),
+		RequestCount:                   assertFloat64NotZero(),
+		Duration:                       assertFloat64NotZero(),
+		Overhead:                       assertFloat64NotZero(),
+		RetryAttempts:                  assertFloat64(float64(0)),
+		"time":                         assertNotEmpty(),
+		StartLocal:                     assertNotEmpty(),
+		StartUTC:                       assertNotEmpty(),
+		"downstream_Content-Type":      assertString("text/plain"),
+		"downstream_Transfer-Encoding": assertString("chunked"),
+		"downstream_Cache-Control":     assertString("no-cache"),
+	}
+
+	config := &types.AccessLog{
+		FilePath: filepath.Join(t.TempDir(), logFileNameSuffix),
+		Format:   JSONFormat,
+	}
+	doLoggingWithAbortedStream(t, config)
+
+	logData, err := os.ReadFile(config.FilePath)
+	require.NoError(t, err)
+
+	jsonData := make(map[string]interface{})
+	err = json.Unmarshal(logData, &jsonData)
+	require.NoError(t, err)
+
+	assert.Equal(t, len(expected), len(jsonData))
+
+	for field, assertion := range expected {
+		assertion(t, jsonData[field])
+		if t.Failed() {
+			return
+		}
+	}
+}
+
 func TestNewLogHandlerOutputStdout(t *testing.T) {
 	testCases := []struct {
 		desc        string
@@ -852,3 +912,89 @@ func logWriterTestHandlerFunc(rw http.ResponseWriter, r *http.Request) {
 
 	rw.WriteHeader(testStatus)
 }
+
+func doLoggingWithAbortedStream(t *testing.T, config *types.AccessLog) {
+	t.Helper()
+
+	logger, err := NewHandler(config)
+	require.NoError(t, err)
+	t.Cleanup(func() {
+		err := logger.Close()
+		require.NoError(t, err)
+	})
+
+	if config.FilePath != "" {
+		_, err = os.Stat(config.FilePath)
+		require.NoError(t, err, "logger should create "+config.FilePath)
+	}
+
+	reqContext, cancelRequest := context.WithCancel(context.Background())
+
+	req := &http.Request{
+		Header: map[string][]string{
+			"User-Agent": {testUserAgent},
+			"Referer":    {testReferer},
+		},
+		Proto:      testProto,
+		Host:       testHostname,
+		Method:     testMethod,
+		RemoteAddr: fmt.Sprintf("%s:%d", testHostname, testPort),
+		URL: &url.URL{
+			User: url.UserPassword(testUsername, ""),
+		},
+		Body: nil,
+	}
+
+	req = req.WithContext(reqContext)
+
+	chain := alice.New()
+	chain = chain.Append(func(next http.Handler) (http.Handler, error) {
+		return recovery.New(context.Background(), next)
+	})
+	chain = chain.Append(capture.Wrap)
+	chain = chain.Append(WrapHandler(logger))
+
+	service := NewFieldHandler(http.HandlerFunc(streamBackend), ServiceURL, "http://stream", nil)
+	service = NewFieldHandler(service, ServiceAddr, "127.0.0.1", nil)
+	service = NewFieldHandler(service, ServiceName, "stream", AddServiceFields)
+
+	handler, err := chain.Then(service)
+	require.NoError(t, err)
+
+	go func() {
+		time.Sleep(499 * time.Millisecond)
+		cancelRequest()
+	}()
+
+	handler.ServeHTTP(httptest.NewRecorder(), req)
+}
+
+func streamBackend(rw http.ResponseWriter, r *http.Request) {
+	// Get the Flusher to flush the response to the client
+	flusher, ok := rw.(http.Flusher)
+	if !ok {
+		http.Error(rw, "Streaming unsupported!", http.StatusInternalServerError)
+		return
+	}
+
+	// Set the headers for streaming
+	rw.Header().Set("Content-Type", "text/plain")
+	rw.Header().Set("Transfer-Encoding", "chunked")
+	rw.Header().Set("Cache-Control", "no-cache")
+
+	for {
+		time.Sleep(100 * time.Millisecond)
+
+		select {
+		case <-r.Context().Done():
+			panic(http.ErrAbortHandler)
+
+		default:
+			if _, err := fmt.Fprint(rw, "FOOBAR!!!!"); err != nil {
+				http.Error(rw, err.Error(), http.StatusInternalServerError)
+				return
+			}
+			flusher.Flush()
+		}
+	}
+}