gorm日志输出到文件

日志原理分析

gorm手册上写着，如果需要自定义logger，则需要实现如下接口：

?

1 2 3 4 5 6 7

type Interface interface {     LogMode(LogLevel) Interface     Info(context.Context, string, ...interface{})     Warn(context.Context, string, ...interface{})     Error(context.Context, string, ...interface{})     Trace(ctx context.Context, begin time.Time, fc func() (sql string, rowsAffected int64), err error) }

 从源码分析一下实现过程

源码里面有个接口定义如下：

?

1 2 3 4

// Writer log writer interface type Writer interface {     Printf(string, ...interface{}) }

日志类定义如下：

?

1 2 3 4 5 6

type logger struct {     Writer     Config     infoStr, warnStr, errStr            string     traceStr, traceErrStr, traceWarnStr string }

logger使用了Write作为一个匿名字段，同时使得logger结构体调用Printf函数时候实际上调用流程是logger.Writer.Printf()。

以Info方法为例：

?

1 2 3 4 5 6

// Info print info func (l logger) Info(ctx context.Context, msg string, data ...interface{}) {     if l.LogLevel >= Info {         l.Printf(l.infoStr+msg, append([]interface{}{utils.FileWithLineNum()}, data...)...)     } }

l.Printf(l.infoStr+msg, append([]interface{}{utils.FileWithLineNum()}, data...)...)函数的实际调用将会是实现了Writer接口的结构体的调用，

结合gorm日志初始化代码中来看

Logger: logger.Default.LogMode(logger.Info)

Default字段的实现如下：

?

1 2 3 4 5 6

Default = New(log.New(os.Stdout, "\r\n", log.LstdFlags), Config{         SlowThreshold:             200 * time.Millisecond,         LogLevel:                  Warn,         IgnoreRecordNotFoundError: false,         Colorful:                  true,     })

log.New(os.Stdout, "\r\n", log.LstdFlags)返回的是一个log.Logger实例，而同时log.Logger也实现了Writer的Printf方法，代码如下：

?

1	func (l *Logger) Printf(format string, v ...any)

　因此gorm日志底层是使用golang日志包的logger来进行日志输出，同时把输出目标设定为os.Stdout来实现打印到标准输出的。

打印到文件

Stdout定义：Stdout = NewFile(uintptr(syscall.Stdout), "/dev/stdout")

因此打印到指定文件的一个简单办法代码实现就是替掉log.New方法中的stdout即可，

如下：

?

1 2 3 4 5 6 7 8 9 10

logfile, _ := os.Create("run.log") db.Session(&gorm.Session{ // 自定session并且GORM日志存放到文件         DryRun: true,         Logger: logger.New(log.New(logfile, "\r\n", log.LstdFlags),             logger.Config{                 SlowThreshold: time.Second,                 LogLevel:      logger.Info,                 Colorful:      true,             }), }).Select(clause.Associations).Delete(inst)

上面的代码在进行delete操作时将把日志保存目标设定为指定的文件run.log。

自己实现日志 

实现目标：输出到文件的同时保留输出到os.Stdout的能力，同时允许扩展到更多输出点。

实现源码如下：

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165

package filelogger   import (     "context"     "errors"     "fmt"     gormlogger "gorm.io/gorm/logger"     "gorm.io/gorm/utils"     "log"     "os"     "syscall"     "time" )   const (     Reset       = "\033[0m"     Red         = "\033[31m"     Green       = "\033[32m"     Yellow      = "\033[33m"     Blue        = "\033[34m"     Magenta     = "\033[35m"     Cyan        = "\033[36m"     White       = "\033[37m"     BlueBold    = "\033[34;1m"     MagentaBold = "\033[35;1m"     RedBold     = "\033[31;1m"     YellowBold  = "\033[33;1m" )   const (     // Silent silent log level     Silent gormlogger.LogLevel = iota + 1     // Error error log level     Error     // Warn warn log level     Warn     // Info info log level     Info )   const DEFAULT_LOGFILE string = "run.log"   type LogConfig struct {     gormlogger.Config     LogFile         string     AddtionalLogger Loggers }   type Loggers []log.Logger   // FileLogger 文件系统日志 type FileLogger struct {     LogConfig     Loggers                             Loggers     infoStr, warnStr, errStr            string     traceStr, traceErrStr, traceWarnStr string }   func NewLogger(config LogConfig) *FileLogger {     if len(config.LogFile) == 0 {         config.LogFile = DEFAULT_LOGFILE     }       loggers := make([]log.Logger, 0)     stdout := os.NewFile(uintptr(syscall.Stdout), "/dev/stdout")     consoleLogger := log.New(stdout, "\r\n", log.LstdFlags)     loggers = append(loggers, *consoleLogger)       logfile, _ := os.Create(config.LogFile)     fileLogger := log.New(logfile, "\r\n", log.LstdFlags)     loggers = append(loggers, *fileLogger)       loggers = append(loggers, config.AddtionalLogger[:]...)       var (         infoStr      = "%s\n[info] "         warnStr      = "%s\n[warn] "         errStr       = "%s\n[error] "         traceStr     = "%s\n[%.3fms] [rows:%v] %s"         traceWarnStr = "%s %s\n[%.3fms] [rows:%v] %s"         traceErrStr  = "%s %s\n[%.3fms] [rows:%v] %s"     )       if config.Colorful {         infoStr = Green + "%s\n" + Reset + Green + "[info] " + Reset         warnStr = BlueBold + "%s\n" + Reset + Magenta + "[warn] " + Reset         errStr = Magenta + "%s\n" + Reset + Red + "[error] " + Reset         traceStr = Green + "%s\n" + Reset + Yellow + "[%.3fms] " + BlueBold + "[rows:%v]" + Reset + " %s"         traceWarnStr = Green + "%s " + Yellow + "%s\n" + Reset + RedBold + "[%.3fms] " + Yellow + "[rows:%v]" + Magenta + " %s" + Reset         traceErrStr = RedBold + "%s " + MagentaBold + "%s\n" + Reset + Yellow + "[%.3fms] " + BlueBold + "[rows:%v]" + Reset + " %s"     }       return &FileLogger{         LogConfig:    config,         Loggers:      loggers,         infoStr:      infoStr,         warnStr:      warnStr,         errStr:       errStr,         traceStr:     traceStr,         traceWarnStr: traceWarnStr,         traceErrStr:  traceErrStr,     } }   func (logger *FileLogger) printf(msg string, data ...interface{}) {     for _, l := range logger.Loggers {         l.Printf(msg, data...)     } }   func (logger *FileLogger) LogMode(lv gormlogger.LogLevel) gormlogger.Interface {     logger.LogLevel = lv     return logger }   func (logger *FileLogger) Info(ctx context.Context, msg string, data ...interface{}) {     if logger.LogLevel >= Info {         logger.printf(logger.infoStr+msg, append([]interface{}{utils.FileWithLineNum()}, data...)...)     } }   func (logger *FileLogger) Warn(ctx context.Context, msg string, data ...interface{}) {     if logger.LogLevel >= Warn {         logger.printf(logger.infoStr+msg, append([]interface{}{utils.FileWithLineNum()}, data...)...)     } }   func (logger *FileLogger) Error(ctx context.Context, msg string, data ...interface{}) {     if logger.LogLevel >= Error {         logger.printf(logger.infoStr+msg, append([]interface{}{utils.FileWithLineNum()}, data...)...)     } }   // Trace 打印sql语句 func (logger *FileLogger) Trace(ctx context.Context, begin time.Time, fc func() (sql string, rowsAffected int64), err error) {     if logger.LogLevel <= Silent {         return     }       elapsed := time.Since(begin)     switch {     case err != nil && logger.LogLevel >= Error && (!errors.Is(err, gormlogger.ErrRecordNotFound) || !logger.IgnoreRecordNotFoundError):         sql, rows := fc()         if rows == -1 {             logger.printf(logger.traceErrStr, utils.FileWithLineNum(), err, float64(elapsed.Nanoseconds())/1e6, "-", sql)         } else {             logger.printf(logger.traceErrStr, utils.FileWithLineNum(), err, float64(elapsed.Nanoseconds())/1e6, rows, sql)         }     case elapsed > logger.SlowThreshold && logger.SlowThreshold != 0 && logger.LogLevel >= Warn:         sql, rows := fc()         slowLog := fmt.Sprintf("SLOW SQL >= %v", logger.SlowThreshold)         if rows == -1 {             logger.printf(logger.traceWarnStr, utils.FileWithLineNum(), slowLog, float64(elapsed.Nanoseconds())/1e6, "-", sql)         } else {             logger.printf(logger.traceWarnStr, utils.FileWithLineNum(), slowLog, float64(elapsed.Nanoseconds())/1e6, rows, sql)         }     case logger.LogLevel == Info:         sql, rows := fc()         if rows == -1 {             logger.printf(logger.traceStr, utils.FileWithLineNum(), float64(elapsed.Nanoseconds())/1e6, "-", sql)         } else {             logger.printf(logger.traceStr, utils.FileWithLineNum(), float64(elapsed.Nanoseconds())/1e6, rows, sql)         }     } }

 

调用代码：

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

secLogfile, _ := os.Create("secLogfile.txt") //定义扩展第二个日志 secLogger := log.New(secLogfile, "\r\n", log.LstdFlags)   anotherLogfile, _ := os.Create("anotherlog.log") anotherLogger := log.New(anotherLogfile, "\r\n", log.LstdFlags) // 定义扩展第三个日志   mylogger := filelogger.NewLogger(filelogger.LogConfig{     LogFile:         "test.log",     AddtionalLogger: append(make(filelogger.Loggers, 0), *anotherLogger, *secLogger), // 附加日志列表     Config: logger.Config{  // gorm日志原始配置项         SlowThreshold:             200 * time.Millisecond,         IgnoreRecordNotFoundError: false,         Colorful:                  true,     }, }).LogMode(filelogger.Info)

运行结果如图：

 

 

 可以看到同时生成了test.log等其他两个日志文件，同时终端输出如下：

2023/02/25 22:28:59 /home/xxx/goworkspace/src/dbapp1/main.go:200
[0.184ms] [rows:2] SELECT * FROM `computers` WHERE `computers`.`UserId` = "31c70e86-3bd6-43d7-ba15-8db25bed48bb" AND `computers`.`del` = 0

2023/02/25 22:28:59 /home/xxx/goworkspace/src/dbapp1/main.go:200
[1.434ms] [rows:1] SELECT * FROM `employeers` WHERE (1=1 and name = '新员工1') AND `employeers`.`del` = 0 LIMIT 1

2023/02/25 22:28:59 /home/xxx/goworkspace/src/dbapp1/main.go:225
[0.035ms] [rows:0] UPDATE `computers` SET `del`=1 WHERE `computers`.`UserId` = "31c70e86-3bd6-43d7-ba15-8db25bed48bb" AND `computers`.`del` = 0
2023/02/25 22:28:59 employeer [31c70e86-3bd6-43d7-ba15-8db25bed48bb] deleted.

2023/02/25 22:28:59 /home/xxx/goworkspace/src/dbapp1/main.go:225
[0.193ms] [rows:0] UPDATE `employeers` SET `del`=1 WHERE `employeers`.`uuid` = "31c70e86-3bd6-43d7-ba15-8db25bed48bb" AND `employeers`.`del` = 0

　　

至此，gorm如何输出到文件及追加到更多文件日志实现。