Added log truncation option

Updated logrus version to match same than most plugins

examples/configs/snap-config-sample.json

@@ -1,6 +1,7 @@
 {
     "log_level": 2,
     "log_path": "/some/log/dir",
+    "log_truncate": false,
     "gomaxprocs": 2,
     "control": {
         "auto_discover_path": "/some/directory/with/plugins",

examples/configs/snap-config-sample.yaml

@@ -10,6 +10,11 @@ log_level: 2
 # the provided directory.
 log_path: /some/log/dir
 
+# log_truncate specifies how the log file with be opened
+# false => append
+# true  => truncate
+log_truncate: false
+
 # Gomaxprocs sets the number of cores to use on the system
 # for snapd to use. Default for gomaxprocs is 1
 gomaxprocs: 2

snapd.go

@@ -60,6 +60,10 @@ var (
 		Usage:  "Path for logs. Empty path logs to stdout.",
 		EnvVar: "SNAP_LOG_PATH",
 	}
+	flLogTruncate = cli.BoolFlag{
+		Name:  "log-truncate",
+		Usage: "Log file truncating mode. Default is false => append (true => truncate).",
+	}
 	flLogLevel = cli.IntFlag{
 		Name:   "log-level, l",
 		Usage:  "1-5 (Debug, Info, Warning, Error, Fatal)",
@@ -93,24 +97,26 @@ var (
 
 // default configuration values
 const (
-	defaultLogLevel   int    = 3
-	defaultGoMaxProcs int    = 1
-	defaultLogPath    string = ""
-	defaultConfigPath string = "/etc/snap/snapd.conf"
+	defaultLogLevel    int    = 3
+	defaultGoMaxProcs  int    = 1
+	defaultLogPath     string = ""
+	defaultLogTruncate bool   = false
+	defaultConfigPath  string = "/etc/snap/snapd.conf"
 )
 
 // holds the configuration passed in through the SNAP config file
 //   Note: if this struct is modified, then the switch statement in the
 //         UnmarshalJSON method in this same file needs to be modified to
 //         match the field mapping that is defined here
 type Config struct {
-	LogLevel   int               `json:"log_level"yaml:"log_level"`
-	GoMaxProcs int               `json:"gomaxprocs"yaml:"gomaxprocs"`
-	LogPath    string            `json:"log_path"yaml:"log_path"`
-	Control    *control.Config   `json:"control"yaml:"control"`
-	Scheduler  *scheduler.Config `json:"scheduler"yaml:"scheduler"`
-	RestAPI    *rest.Config      `json:"restapi"yaml:"restapi"`
-	Tribe      *tribe.Config     `json:"tribe"yaml:"tribe"`
+	LogLevel    int               `json:"log_level,omitempty"yaml:"log_level,omitempty"`
+	GoMaxProcs  int               `json:"gomaxprocs,omitempty"yaml:"gomaxprocs,omitempty"`
+	LogPath     string            `json:"log_path,omitempty"yaml:"log_path,omitempty"`
+	LogTruncate bool              `json:"log_truncate,omitempty"yaml:"log_truncate,omitempty"`
+	Control     *control.Config   `json:"control,omitempty"yaml:"control,omitempty"`
+	Scheduler   *scheduler.Config `json:"scheduler,omitempty"yaml:"scheduler,omitempty"`
+	RestAPI     *rest.Config      `json:"restapi,omitempty"yaml:"restapi,omitempty"`
+	Tribe       *tribe.Config     `json:"tribe,omitempty"yaml:"tribe,omitempty"`
 }
 
 const (
@@ -129,6 +135,10 @@ const (
 				"description": "path to log file for snapd to use",
 				"type": "string"
 			},
+			"log_truncate": {
+				"description": "truncate log file default is false",
+				"type": "boolean"
+			},
 			"gomaxprocs": {
 				"description": "value to be used for gomaxprocs",
 				"type": "integer",
@@ -179,6 +189,7 @@ func main() {
 	app.Flags = []cli.Flag{
 		flLogLevel,
 		flLogPath,
+		flLogTruncate,
 		flMaxProcs,
 		flConfig,
 	}
@@ -227,8 +238,11 @@ func action(ctx *cli.Context) {
 		if !f.IsDir() {
 			log.Fatal("log path provided must be a directory")
 		}
-
-		file, err := os.OpenFile(fmt.Sprintf("%s/snapd.log", logPath), os.O_RDWR|os.O_CREATE|os.O_APPEND, 0666)
+		aMode := os.O_APPEND
+		if cfg.LogTruncate {
+			aMode = os.O_TRUNC
+		}
+		file, err := os.OpenFile(fmt.Sprintf("%s/snapd.log", logPath), os.O_RDWR|os.O_CREATE|aMode, 0666)
 		if err != nil {
 			log.Fatal(err)
 		}
@@ -435,13 +449,14 @@ func action(ctx *cli.Context) {
 // get the default snapd configuration
 func getDefaultConfig() *Config {
 	return &Config{
-		LogLevel:   defaultLogLevel,
-		GoMaxProcs: defaultGoMaxProcs,
-		LogPath:    defaultLogPath,
-		Control:    control.GetDefaultConfig(),
-		Scheduler:  scheduler.GetDefaultConfig(),
-		RestAPI:    rest.GetDefaultConfig(),
-		Tribe:      tribe.GetDefaultConfig(),
+		LogLevel:    defaultLogLevel,
+		GoMaxProcs:  defaultGoMaxProcs,
+		LogPath:     defaultLogPath,
+		LogTruncate: defaultLogTruncate,
+		Control:     control.GetDefaultConfig(),
+		Scheduler:   scheduler.GetDefaultConfig(),
+		RestAPI:     rest.GetDefaultConfig(),
+		Tribe:       tribe.GetDefaultConfig(),
 	}
 }
 
@@ -560,6 +575,7 @@ func applyCmdLineFlags(cfg *Config, ctx *cli.Context) {
 	cfg.GoMaxProcs = setIntVal(cfg.GoMaxProcs, ctx, "max-procs")
 	cfg.LogLevel = setIntVal(cfg.LogLevel, ctx, "log-level")
 	cfg.LogPath = setStringVal(cfg.LogPath, ctx, "log-path")
+	cfg.LogTruncate = setBoolVal(cfg.LogTruncate, ctx, "log-truncate")
 	// next for the flags related to the control package
 	cfg.Control.MaxRunningPlugins = setIntVal(cfg.Control.MaxRunningPlugins, ctx, "max-running-plugins")
 	cfg.Control.PluginTrust = setIntVal(cfg.Control.PluginTrust, ctx, "plugin-trust")
@@ -680,6 +696,10 @@ func (c *Config) UnmarshalJSON(data []byte) error {
 			if err := json.Unmarshal(v, &(c.LogPath)); err != nil {
 				return fmt.Errorf("%v (while parsing 'log_path')", err)
 			}
+		case "log_truncate":
+			if err := json.Unmarshal(v, &(c.LogTruncate)); err != nil {
+				return fmt.Errorf("%v (while parsing 'log_truncate')", err)
+			}
 		case "control":
 			if err := json.Unmarshal(v, c.Control); err != nil {
 				return err