cmd/cli: better error message when log file is empty

While at it, also record the size of logs being sent in debug/error
message.

cmd/cli/commands.go

@@ -19,6 +19,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/docker/go-units"
 	"github.com/kardianos/service"
 	"github.com/minio/selfupdate"
 	"github.com/olekukonko/tablewriter"
@@ -48,17 +49,24 @@ func initLogCmd() *cobra.Command {
 			}
 			defer resp.Body.Close()
 			switch resp.StatusCode {
-			case http.StatusOK:
-				mainLog.Load().Notice().Msg("runtime logs sent successfully")
 			case http.StatusServiceUnavailable:
 				mainLog.Load().Warn().Msg("runtime logs could only be sent once per minute")
-			default:
-				buf, err := io.ReadAll(resp.Body)
-				if err != nil {
-					mainLog.Load().Fatal().Err(err).Msg("failed to read response body")
-				}
-				mainLog.Load().Error().Msg("failed to send logs")
-				mainLog.Load().Error().Msg(string(buf))
+				return
+			case http.StatusMovedPermanently:
+				mainLog.Load().Warn().Msg("runtime debugs log is not enabled")
+				mainLog.Load().Warn().Msg(`ctrld may be run without "--cd" flag or logging is already enabled`)
+				return
+			}
+			var logs logSentResponse
+			if err := json.NewDecoder(resp.Body).Decode(&logs); err != nil {
+				mainLog.Load().Fatal().Err(err).Msg("failed to decode sent logs result")
+			}
+			size := units.BytesSize(float64(logs.Size))
+			if logs.Error == "" {
+				mainLog.Load().Notice().Msgf("runtime logs sent successfully (%s)", size)
+			} else {
+				mainLog.Load().Error().Msgf("failed to send logs (%s)", size)
+				mainLog.Load().Error().Msg(logs.Error)
 			}
 		},
 	}
@@ -85,6 +93,11 @@ func initLogCmd() *cobra.Command {
 				return
 			case http.StatusBadRequest:
 				mainLog.Load().Warn().Msg("runtime debugs log is not available")
+				buf, err := io.ReadAll(resp.Body)
+				if err != nil {
+					mainLog.Load().Fatal().Err(err).Msg("failed to read response body")
+				}
+				mainLog.Load().Warn().Msgf("ctrld process response:\n\n%s\n", string(buf))
 				return
 			case http.StatusOK:
 			}

cmd/cli/control_server.go

@@ -217,7 +217,7 @@ func (p *prog) registerControlServerHandler() {
 	p.cs.register(viewLogsPath, http.HandlerFunc(func(w http.ResponseWriter, request *http.Request) {
 		data, err := p.logContent()
 		if err != nil {
-			w.WriteHeader(http.StatusBadRequest)
+			http.Error(w, err.Error(), http.StatusBadRequest)
 			return
 		}
 		if len(data) == 0 {
@@ -236,7 +236,7 @@ func (p *prog) registerControlServerHandler() {
 		}
 		data, err := p.logContent()
 		if err != nil {
-			w.WriteHeader(http.StatusBadRequest)
+			http.Error(w, err.Error(), http.StatusBadRequest)
 			return
 		}
 		if len(data) == 0 {
@@ -249,11 +249,17 @@ func (p *prog) registerControlServerHandler() {
 			LogFile: logFile,
 		}
 		mainLog.Load().Debug().Msg("sending log file to ControlD server")
+		resp := logSentResponse{Size: len(data)}
 		if err := controld.SendLogs(req, cdDev); err != nil {
 			mainLog.Load().Error().Msgf("could not send log file to ControlD server: %v", err)
-			http.Error(w, err.Error(), http.StatusInternalServerError)
+			resp.Error = err.Error()
+			w.WriteHeader(http.StatusInternalServerError)
 		} else {
 			mainLog.Load().Debug().Msg("sending log file successfully")
+			w.WriteHeader(http.StatusOK)
+		}
+		if err := json.NewEncoder(w).Encode(&resp); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
 		}
 		p.internalLogSent = time.Now()
 	}))

cmd/cli/log_writer.go

@@ -24,6 +24,11 @@ type logViewResponse struct {
 	Data string `json:"data"`
 }
 
+type logSentResponse struct {
+	Size  int    `json:"size"`
+	Error string `json:"error"`
+}
+
 // logWriter is an internal buffer to keep track of runtime log when no logging is enabled.
 type logWriter struct {
 	mu   sync.Mutex
@@ -118,6 +123,9 @@ func (p *prog) logContent() ([]byte, error) {
 		lw.mu.Lock()
 		data = lw.buf.Bytes()
 		lw.mu.Unlock()
+		if len(data) == 0 {
+			return nil, errors.New("internal log is empty")
+		}
 	} else {
 		if p.cfg.Service.LogPath == "" {
 			return nil, nil
@@ -127,6 +135,9 @@ func (p *prog) logContent() ([]byte, error) {
 			return nil, err
 		}
 		data = buf
+		if len(data) == 0 {
+			return nil, errors.New("log file is empty")
+		}
 	}
 	return data, nil
 }