logging into file in background mode (#575)

* logging into file in background mode

* --logfile -> --log

* update docs

cmd/mount.go

@@ -200,7 +200,7 @@ func mount(c *cli.Context) error {
 		}
 		// The default log to syslog is only in daemon mode.
 		utils.InitLoggers(!c.Bool("no-syslog"))
-		err := makeDaemon(conf.Format.Name, conf.Mountpoint)
+		err := makeDaemon(c, conf.Format.Name, conf.Mountpoint)
 		if err != nil {
 			logger.Fatalf("Failed to make daemon: %s", err)
 		}

cmd/mount_unix.go

@@ -48,8 +48,9 @@ func checkMountpoint(name, mp string) {
 	logger.Fatalf("fail to mount after 10 seconds, please mount in foreground")
 }
 
-func makeDaemon(name, mp string) error {
-	onExit := func(stage int) error {
+func makeDaemon(c *cli.Context, name, mp string) error {
+	var attrs godaemon.DaemonAttr
+	attrs.OnExit = func(stage int) error {
 		if stage != 0 {
 			return nil
 		}
@@ -70,8 +71,14 @@ func makeDaemon(name, mp string) error {
 				}
 			}
 		}
+		var err error
+		logfile := c.String("logfile")
+		attrs.Stdout, err = os.OpenFile(logfile, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0755)
+		if err != nil {
+			logger.Errorf("open log file %s: %s", logfile, err)
+		}
 	}
-	_, _, err := godaemon.MakeDaemon(&godaemon.DaemonAttr{OnExit: onExit})
+	_, _, err := godaemon.MakeDaemon(&attrs)
 	return err
 }
 
@@ -86,6 +93,11 @@ func mount_flags() []cli.Flag {
 			Name:  "no-syslog",
 			Usage: "disable syslog",
 		},
+		&cli.StringFlag{
+			Name:  "log",
+			Value: "/var/log/juicefs.log",
+			Usage: "path of log file when running in background",
+		},
 		&cli.StringFlag{
 			Name:  "o",
 			Usage: "other FUSE options",

cmd/mount_windows.go

@@ -48,7 +48,7 @@ func mount_flags() []cli.Flag {
 	}
 }
 
-func makeDaemon(name, mp string) error {
+func makeDaemon(c *cli.Context, name, mp string) error {
 	logger.Warnf("Cannot run in background in Windows.")
 	return nil
 }

docs/en/command_reference.md

@@ -164,6 +164,9 @@ run in background (default: false)
 `--no-syslog`\
 disable syslog (default: false)
 
+`--log value`\
+path of log file when running in background (default: /var/log/juicefs.log)
+
 `-o value`\
 other FUSE options (see [this document](fuse_mount_options.md) for more information)
 

docs/en/fault_diagnosis_and_analysis.md

@@ -2,7 +2,7 @@
 
 ## Error Log
 
-When JuiceFS run in background (through [`-d` option](command_reference.md#juicefs-mount) when mount volume), logs will output to syslog. Depending on your operating system, you can get the logs through different commands:
+When JuiceFS run in background (through [`-d` option](command_reference.md#juicefs-mount) when mount volume), logs will output to syslog and /var/log/juicefs.log (v0.15+). Depending on your operating system, you can get the logs through different commands:
 
 ```bash
 # macOS
@@ -13,6 +13,9 @@ $ cat /var/log/syslog | grep 'juicefs'
 
 # CentOS based system
 $ cat /var/log/messages | grep 'juicefs'
+
+# v0.15+
+$ tail -n 100 /var/log/juicefs.log
 ```
 
 There are 4 log levels. You can use the `grep` command to filter different levels of logs for performance analysis or troubleshooting:

docs/zh_cn/command_reference.md

@@ -164,6 +164,9 @@ juicefs mount [command options] META-URL MOUNTPOINT
 `--no-syslog`\
 禁用系统日志 (默认: false)
 
+`--log value`\
+后台运行时日志文件的位置 (默认: /var/log/juicefs.log)
+
 `-o value`\
 其他 FUSE 选项 (参见[此文档](fuse_mount_options.md)来了解更多信息)
 

docs/zh_cn/fault_diagnosis_and_analysis.md

@@ -2,7 +2,7 @@
 
 ## 错误日志
 
-当 JuiceFS 通过 `-d` 选项在后台运行时，日志会输出到 syslog。取决于你使用的操作系统，你可以通过不同的命令获取日志：
+当 JuiceFS 通过 `-d` 选项在后台运行时，日志会输出到系统日志和 /var/log/juicefs.log (v0.15+)。取决于你使用的操作系统，你可以通过不同的命令获取日志：
 
 ```bash
 # macOS
@@ -13,6 +13,9 @@ $ cat /var/log/syslog | grep 'juicefs'
 
 # CentOS based system
 $ cat /var/log/messages | grep 'juicefs'
+
+# v0.15+
+$ tail -n 100 /var/log/juicefs.log
 ```
 
 日志等级有 4 种。你可以使用 `grep` 命令过滤显示不同等级的日志信息，从而进行性能统计和故障追踪。

go.mod

@@ -28,7 +28,7 @@ require (
 	github.com/huaweicloud/huaweicloud-sdk-go-obs v0.0.0-20190127152727-3a9e1f8023d5
 	github.com/hungys/go-lz4 v0.0.0-20170805124057-19ff7f07f099
 	github.com/jcmturner/gokrb5/v8 v8.4.2
-	github.com/juicedata/godaemon v0.0.0-20210118074000-659b6681b236
+	github.com/juicedata/godaemon v0.0.0-20210629045518-3da5144a127d
 	github.com/juju/ratelimit v1.0.1
 	github.com/kr/fs v0.1.0 // indirect
 	github.com/ks3sdklib/aws-sdk-go v0.0.0-20180820074416-dafab05ad142

go.sum

@@ -373,6 +373,8 @@ github.com/juicedata/go-fuse/v2 v2.1.1-0.20210629082323-0ec79f5f0a45 h1:EKaeYSLT
 github.com/juicedata/go-fuse/v2 v2.1.1-0.20210629082323-0ec79f5f0a45/go.mod h1:oRyA5eK+pvJyv5otpO/DgccS8y/RvYMaO00GgRLGryc=
 github.com/juicedata/godaemon v0.0.0-20210118074000-659b6681b236 h1:py4S1ZTRfz5hIvrhu83YSw7t0Z621+VrmmZBqSkQn5c=
 github.com/juicedata/godaemon v0.0.0-20210118074000-659b6681b236/go.mod h1:dlxKkLh3qAIPtgr2U/RVzsZJDuXA1ffg+Njikfmhvgw=
+github.com/juicedata/godaemon v0.0.0-20210629045518-3da5144a127d h1:kpQMvNZJKGY3PTt7OSoahYc4nM0HY67SvK0YyS0GLwA=
+github.com/juicedata/godaemon v0.0.0-20210629045518-3da5144a127d/go.mod h1:dlxKkLh3qAIPtgr2U/RVzsZJDuXA1ffg+Njikfmhvgw=
 github.com/juicedata/minio v0.0.0-20210222051636-e7cabdf948f4 h1:/Klbj2LgJnqWrVfK2RtsqNQm649uXi2diLc/2X3eis4=
 github.com/juicedata/minio v0.0.0-20210222051636-e7cabdf948f4/go.mod h1:pQt7BggRNk3m4ZLGmtZ8ShrWe70RvyeXsHljoapikM0=
 github.com/juju/ratelimit v1.0.1 h1:+7AIFJVQ0EQgq/K9+0Krm7m530Du7tIz0METWzN0RgY=