Detailed introduction to the log module in golang

The following editor will bring you a detailed explanation of log rotate in golang. The editor thinks it is quite good, so I will share it with you now and give it as a reference for everyone. Let’s follow the editor and take a look

Operating system: CentOS 6.9_x64

go language version: 1.8.3

Problem description

The log module of golang provides the log writing function. The sample code is as follows:

/* golang log example */ package main import ( "log" "os" ) func main() { logFile,err := os.Create("test1.log") defer logFile.Close() if err != nil { log.Fatalln("open file error!") } logger := log.New(logFile,"[Debug]",log.Ldate | log.Ltime | log.Lshortfile) logger.Println("test debug message") logger.SetPrefix("[Info]") logger.Println("test info message") }

Operating effect:

[root@local t2]# go build logTest1.go [root@local t2]# ./logTest1 [root@local t2]# cat test1.log [Debug]2017/06/13 23:18:36 logTest1.go:19: test debug message [Info]2017/06/13 23:18:36 logTest1.go:21: test info message [root@local t2]#

The log module of the go language does not provide log rotate interface, but in actual development we need this function:

We don’t want a single log to be too large, otherwise the text editor cannot open it and it will be difficult to view;

We also don’t want to occupy too much storage Space, you can specify the maximum number of log files to store.

Solution

Achieved with the help of buffered channel.

The sample code is as follows:

/* golang log rotate example */ package main import ( "fmt" "log" "os" "time" ) const ( BACKUP_COUNT = 5 MAX_FILE_BYTES = 2 * 1024 ) func doRotate(fPrefix string) { for j := BACKUP_COUNT; j >= 1; j-- { curFileName := fmt.Sprintf("%s_%d.log",fPrefix,j) k := j-1 preFileName := fmt.Sprintf("%s_%d.log",fPrefix,k) if k == 0 { preFileName = fmt.Sprintf("%s.log", fPrefix) } _,err := os.Stat(curFileName) if err == nil { os.Remove(curFileName) fmt.Println("remove : ", curFileName) } _,err = os.Stat(preFileName) if err == nil { fmt.Println("rename : ", preFileName, " => ", curFileName) err = os.Rename(preFileName, curFileName) if err != nil { fmt.Println(err) } } } } func NewLogger(fPrefix string) (*log.Logger, *os.File) { var logger *log.Logger fileName := fmt.Sprintf("%s.log", fPrefix) fmt.Println("fileName :", fileName) logFile, err := os.OpenFile(fileName, os.O_RDWR|os.O_CREATE|os.O_APPEND, 0666) if err != nil { fmt.Println("open file error!") } else { logger = log.New(logFile, "[Debug]", log.Ldate|log.Ltime|log.Lshortfile) } return logger, logFile } func logWorker(msgQueue <-chan string) { fPrefix := "msg" logger, logFile := NewLogger(fPrefix) for msg := range msgQueue { logger.Println(msg) fi, err2 := logFile.Stat() if err2 == nil { if fi.Size() > MAX_FILE_BYTES { logFile.Close() doRotate(fPrefix) logger,logFile = NewLogger(fPrefix) } } } logFile.Close() } func main() { msgQueue := make(chan string, 1000) go logWorker(msgQueue) for j := 1; j <= 1000; j++ { msgQueue <- fmt.Sprintf("msg_%d", j) time.Sleep(1 * time.Second) } close(msgQueue) return }

The running effect is as follows:

[root@local t2]# ./logRotateTest1 fileName : msg.log rename : msg.log => msg_1.log fileName : msg.log rename : msg_1.log => msg_2.log rename : msg.log => msg_1.log fileName : msg.log rename : msg_2.log => msg_3.log rename : msg_1.log => msg_2.log rename : msg.log => msg_1.log fileName : msg.log ^C

Discussion

This is just a simple sample code that implements log rotate. More functions need to be developed by yourself.

Okay, that’s all, I hope it helps.

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