[feat:] Add Log tailing

pkg/cmd/dev/cmd.go

@@ -69,13 +69,14 @@ func DevStopCommand() *cobra.Command {
 }
 
 func DevLogsCommand() *cobra.Command {
-	opts := &DevBaseOptions{}
+	opts := &DevLogsOptions{}
 	cmd := &cobra.Command{
 		Use:   "logs",
 		Short: devLogsShortDesc,
 		Long:  devLogsLongDesc,
 		Run:   runLogsCommand(opts),
 	}
+	cmd.Flags().BoolVarP(&opts.follow, "follow", "f", false, "Stream the log file")
 	return cmd
 }
 
@@ -113,14 +114,14 @@ func runStopCommand(opts *DevBaseOptions) func(cmd *cobra.Command, args []string
 	}
 }
 
-func runLogsCommand(opts *DevBaseOptions) func(cmd *cobra.Command, args []string) {
+func runLogsCommand(opts *DevLogsOptions) func(cmd *cobra.Command, args []string) {
 	return func(cmd *cobra.Command, args []string) {
 		if err := opts.complete(cmd.Context(), args); err != nil {
 			output.Errorf("failed to complete options: %s", err)
 			return
 		}
 
-		err := harness.PrintLogs(opts.configHome, cmd.OutOrStdout())
+		err := harness.PrintLogs(opts.configHome, cmd.OutOrStdout(), opts.follow)
 		if err != nil {
 			output.Errorln(err)
 			os.Exit(1)

pkg/cmd/dev/opts.go

@@ -29,6 +29,11 @@ type DevBaseOptions struct {
 	configHome string
 }
 
+type DevLogsOptions struct {
+	DevBaseOptions
+	follow bool
+}
+
 func (opts *DevBaseOptions) complete(ctx context.Context, args []string) error {
 	configHome, ok := ctx.Value(constants.ConfigKey{}).(string)
 	if !ok {

pkg/lib/harness/llm-harness.go

@@ -17,6 +17,7 @@
 package harness
 
 import (
+	"bufio"
 	"errors"
 	"fmt"
 	"io"
@@ -28,6 +29,7 @@ import (
 	"strconv"
 	"strings"
 	"syscall"
+	"time"
 
 	"kitops/pkg/lib/constants"
 	"kitops/pkg/output"
@@ -169,7 +171,7 @@ func (harness *LLMHarness) Stop() error {
 	return nil
 }
 
-func PrintLogs(configHome string, w io.Writer) error {
+func PrintLogs(configHome string, w io.Writer, follow bool) error {
 	harnessPath := constants.HarnessPath(configHome)
 	logPath := filepath.Join(harnessPath, constants.HarnessLogFile)
 	logFile, err := os.Open(logPath)
@@ -181,10 +183,35 @@ func PrintLogs(configHome string, w io.Writer) error {
 		return fmt.Errorf("error reading log file: %w", err)
 	}
 	defer logFile.Close()
-	if _, err = io.Copy(w, logFile); err != nil {
-		return fmt.Errorf("failed to print log file: %w", err)
+	reader := bufio.NewReader(logFile)
+	for {
+		line, err := reader.ReadString('\n')
+		if err != nil {
+			if err == io.EOF {
+				if !follow {
+					return nil
+				}
+				time.Sleep(1 * time.Second)
+				serverStatus := checkExistence(configHome)
+				if serverStatus {
+					return fmt.Errorf("server stopped")
+				}
+				continue
+			} else {
+				return fmt.Errorf("failed to print log file: %w", err)
+			}
+		}
+		if _, err := w.Write([]byte(line)); err != nil {
+			return fmt.Errorf("failed to write to output: %w", err)
+		}
 	}
-	return nil
+}
+
+func checkExistence(configHome string) bool {
+	pidFile := filepath.Join(constants.HarnessPath(configHome), constants.HarnessProcessFile)
+
+	_, err := readPIDFromFile(pidFile)
+	return os.IsNotExist(err)
 }
 
 func isProcessRunning(pid int) bool {