cmd, internal, log: write logs into 1MB file chunks

cmd/geth/main.go

@@ -185,7 +185,7 @@ func init() {
 
 	app.Before = func(ctx *cli.Context) error {
 		runtime.GOMAXPROCS(runtime.NumCPU())
-		if err := debug.Setup(ctx); err != nil {
+		if err := debug.Setup(ctx, ctx.GlobalBool(utils.DashboardEnabledFlag.Name), utils.DataDirFlag.Value.Value); err != nil {
 			return err
 		}
 		// Start system runtime metrics collection

cmd/swarm/main.go

@@ -363,7 +363,7 @@ DEPRECATED: use 'swarm db clean'.
 	app.Flags = append(app.Flags, swarmmetrics.Flags...)
 	app.Before = func(ctx *cli.Context) error {
 		runtime.GOMAXPROCS(runtime.NumCPU())
-		if err := debug.Setup(ctx); err != nil {
+		if err := debug.Setup(ctx, ctx.GlobalBool(utils.DashboardEnabledFlag.Name), utils.DataDirFlag.Value.Value); err != nil {
 			return err
 		}
 		swarmmetrics.Setup(ctx)

internal/debug/flags.go

@@ -108,13 +108,17 @@ 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 {
+func Setup(ctx *cli.Context, dashboard bool, path string) error {
 	// logging
 	log.PrintOrigins(ctx.GlobalBool(debugFlag.Name))
 	glogger.Verbosity(log.Lvl(ctx.GlobalInt(verbosityFlag.Name)))
 	glogger.Vmodule(ctx.GlobalString(vmoduleFlag.Name))
 	glogger.BacktraceAt(ctx.GlobalString(backtraceAtFlag.Name))
-	log.Root().SetHandler(glogger)
+	h := log.Handler(glogger)
+	if dashboard {
+		h = log.MultiHandler(h, log.DashboardHandler(path+"/dashboard/logs"))
+	}
+	log.Root().SetHandler(h)
 
 	// profiling, tracing
 	runtime.MemProfileRate = ctx.GlobalInt(memprofilerateFlag.Name)

log/handler.go

@@ -9,6 +9,7 @@ import (
 	"sync"
 
 	"github.com/go-stack/stack"
+	"strings"
 )
 
 // Handler defines where and how log records are written.
@@ -70,6 +71,36 @@ func FileHandler(path string, fmtr Format) (Handler, error) {
 	return closingHandler{f, StreamHandler(f, fmtr)}, nil
 }
 
+// DashboardHandler returns a handler which writes log records to file chunks
+// at the given path. When a file's size reaches the 1MB, the handler creates
+// a new file named with the timestamp of the first log record it will contain.
+func DashboardHandler(path string) Handler {
+	if _, err := os.Stat(path); os.IsNotExist(err) {
+		if err = os.MkdirAll(path, 0755); err != nil {
+			// TODO (kurkomisi): handle error?
+			return DiscardHandler()
+		}
+	}
+
+	var size uint
+	maxSize := uint(1048576)
+	var h Handler
+	formatter := JsonFormat()
+
+	return FuncHandler(func(r *Record) error {
+		var err error
+		if h == nil || size > maxSize {
+			if h, err = FileHandler(fmt.Sprintf("%s/%s.log", path,
+				strings.Replace(r.Time.Format("060102150405.00"), ".", "", 1)), formatter); err != nil {
+				return err
+			}
+			size = 0
+		}
+		size += uint(len(formatter.Format(r)))
+		return h.Log(r)
+	})
+}
+
 // NetHandler opens a socket to the given address and writes records
 // over the connection.
 func NetHandler(network, addr string, fmtr Format) (Handler, error) {