cmd/geth: enable log rotation (#26843)

This change enables log rotation, which can be activated using the flag --log.rotate. Additional parameters that can be given are: 

  - log.maxsize to set maximum size before files are rotated,
  - log.maxbackups to set how many files are retailed, 
  - log.maxage to configure max age of rotated files, 
  - log.compress whether to compress rotated files

The way to configure location of the logfile(s) is left unchanged, via the `log.logfile` parameter.  

---------

Co-authored-by: Martin Holst Swende <martin@swende.se>

internal/debug/flags.go

@@ -20,8 +20,9 @@ import (
 	"fmt"
 	"io"
 	"net/http"
-	_ "net/http/pprof" // nolint: gosec
+	_ "net/http/pprof"
 	"os"
+	"path/filepath"
 	"runtime"
 
 	"github.com/ethereum/go-ethereum/internal/flags"
@@ -32,6 +33,7 @@ import (
 	"github.com/mattn/go-colorable"
 	"github.com/mattn/go-isatty"
 	"github.com/urfave/cli/v2"
+	"gopkg.in/natefinch/lumberjack.v2"
 )
 
 var Memsize memsizeui.Handler
@@ -76,6 +78,34 @@ var (
 		Usage:    "Prepends log messages with call-site location (file and line number)",
 		Category: flags.LoggingCategory,
 	}
+	logRotateFlag = &cli.BoolFlag{
+		Name:  "log.rotate",
+		Usage: "Enables log file rotation",
+	}
+	logMaxSizeMBsFlag = &cli.IntFlag{
+		Name:     "log.maxsize",
+		Usage:    "Maximum size in MBs of a single log file",
+		Value:    100,
+		Category: flags.LoggingCategory,
+	}
+	logMaxBackupsFlag = &cli.IntFlag{
+		Name:     "log.maxbackups",
+		Usage:    "Maximum number of log files to retain",
+		Value:    10,
+		Category: flags.LoggingCategory,
+	}
+	logMaxAgeFlag = &cli.IntFlag{
+		Name:     "log.maxage",
+		Usage:    "Maximum number of days to retain a log file",
+		Value:    30,
+		Category: flags.LoggingCategory,
+	}
+	logCompressFlag = &cli.BoolFlag{
+		Name:     "log.compress",
+		Usage:    "Compress the log files",
+		Value:    false,
+		Category: flags.LoggingCategory,
+	}
 	pprofFlag = &cli.BoolFlag{
 		Name:     "pprof",
 		Usage:    "Enable the pprof HTTP server",
@@ -120,11 +150,16 @@ var (
 var Flags = []cli.Flag{
 	verbosityFlag,
 	vmoduleFlag,
+	backtraceAtFlag,
+	debugFlag,
 	logjsonFlag,
 	logFormatFlag,
 	logFileFlag,
-	backtraceAtFlag,
-	debugFlag,
+	logRotateFlag,
+	logMaxSizeMBsFlag,
+	logMaxBackupsFlag,
+	logMaxAgeFlag,
+	logCompressFlag,
 	pprofFlag,
 	pprofAddrFlag,
 	pprofPortFlag,
@@ -148,44 +183,71 @@ func init() {
 // Setup initializes profiling and logging based on the CLI flags.
 // It should be called as early as possible in the program.
 func Setup(ctx *cli.Context) error {
-	logFile := ctx.String(logFileFlag.Name)
-	useColor := logFile == "" && os.Getenv("TERM") != "dumb" && (isatty.IsTerminal(os.Stderr.Fd()) || isatty.IsCygwinTerminal(os.Stderr.Fd()))
-
-	var logfmt log.Format
-	switch ctx.String(logFormatFlag.Name) {
-	case "json":
-		logfmt = log.JSONFormat()
-	case "logfmt":
-		logfmt = log.LogfmtFormat()
-	case "terminal":
-		logfmt = log.TerminalFormat(useColor)
-	case "":
+	var (
+		logfmt     log.Format
+		output     = io.Writer(os.Stderr)
+		logFmtFlag = ctx.String(logFormatFlag.Name)
+	)
+	switch {
+	case ctx.Bool(logjsonFlag.Name):
 		// Retain backwards compatibility with `--log.json` flag if `--log.format` not set
-		if ctx.Bool(logjsonFlag.Name) {
-			defer log.Warn("The flag '--log.json' is deprecated, please use '--log.format=json' instead")
-			logfmt = log.JSONFormat()
-		} else {
-			logfmt = log.TerminalFormat(useColor)
+		defer log.Warn("The flag '--log.json' is deprecated, please use '--log.format=json' instead")
+		logfmt = log.JSONFormat()
+	case logFmtFlag == "json":
+		logfmt = log.JSONFormat()
+	case logFmtFlag == "logfmt":
+		logfmt = log.LogfmtFormat()
+	case logFmtFlag == "", logFmtFlag == "terminal":
+		useColor := (isatty.IsTerminal(os.Stderr.Fd()) || isatty.IsCygwinTerminal(os.Stderr.Fd())) && os.Getenv("TERM") != "dumb"
+		if useColor {
+			output = colorable.NewColorableStderr()
 		}
+		logfmt = log.TerminalFormat(useColor)
 	default:
 		// Unknown log format specified
 		return fmt.Errorf("unknown log format: %v", ctx.String(logFormatFlag.Name))
 	}
-
-	if logFile != "" {
-		var err error
-		logOutputStream, err = log.FileHandler(logFile, logfmt)
-		if err != nil {
-			return err
+	var (
+		stdHandler = log.StreamHandler(output, logfmt)
+		ostream    = stdHandler
+		logFile    = ctx.String(logFileFlag.Name)
+		rotation   = ctx.Bool(logRotateFlag.Name)
+	)
+	if len(logFile) > 0 {
+		if err := validateLogLocation(filepath.Dir(logFile)); err != nil {
+			return fmt.Errorf("failed to initiatilize file logger: %v", err)
 		}
-	} else {
-		output := io.Writer(os.Stderr)
-		if useColor {
-			output = colorable.NewColorableStderr()
-		}
-		logOutputStream = log.StreamHandler(output, logfmt)
 	}
-	glogger.SetHandler(logOutputStream)
+	context := []interface{}{"rotate", rotation}
+	if len(logFmtFlag) > 0 {
+		context = append(context, "format", logFmtFlag)
+	} else {
+		context = append(context, "format", "terminal")
+	}
+	if rotation {
+		// Lumberjack uses <processname>-lumberjack.log in is.TempDir() if empty.
+		// so typically /tmp/geth-lumberjack.log on linux
+		if len(logFile) > 0 {
+			context = append(context, "location", logFile)
+		} else {
+			context = append(context, "location", filepath.Join(os.TempDir(), "geth-lumberjack.log"))
+		}
+		ostream = log.MultiHandler(log.StreamHandler(&lumberjack.Logger{
+			Filename:   logFile,
+			MaxSize:    ctx.Int(logMaxSizeMBsFlag.Name),
+			MaxBackups: ctx.Int(logMaxBackupsFlag.Name),
+			MaxAge:     ctx.Int(logMaxAgeFlag.Name),
+			Compress:   ctx.Bool(logCompressFlag.Name),
+		}, logfmt), stdHandler)
+	} else if logFile != "" {
+		if logOutputStream, err := log.FileHandler(logFile, logfmt); err != nil {
+			return err
+		} else {
+			ostream = log.MultiHandler(logOutputStream, stdHandler)
+			context = append(context, "location", logFile)
+		}
+	}
+	glogger.SetHandler(ostream)
 
 	// logging
 	verbosity := ctx.Int(verbosityFlag.Name)
@@ -236,6 +298,9 @@ func Setup(ctx *cli.Context) error {
 		// It cannot be imported because it will cause a cyclical dependency.
 		StartPProf(address, !ctx.IsSet("metrics.addr"))
 	}
+	if len(logFile) > 0 || rotation {
+		log.Info("Logging configured", context...)
+	}
 	return nil
 }
 
@@ -263,3 +328,17 @@ func Exit() {
 		closer.Close()
 	}
 }
+
+func validateLogLocation(path string) error {
+	if err := os.MkdirAll(path, os.ModePerm); err != nil {
+		return fmt.Errorf("error creating the directory: %w", err)
+	}
+	// Check if the path is writable by trying to create a temporary file
+	tmp := filepath.Join(path, "tmp")
+	if f, err := os.Create(tmp); err != nil {
+		return err
+	} else {
+		f.Close()
+	}
+	return os.Remove(tmp)
+}