Simplelog is a log package mainly with a focus on simplicity, ease of use and performance.
Once started, the simple logger runs as a service and listens for logging requests. The simple logger writes log records to either standard out, a log file, or standard out and a log file simultaneously (multi log).
In order to use or work with the simplelog package, the following set of functions were exposed to be used as the simplelog API:
// SetPrefix sets the prefix for log records.
func SetPrefix(destination int, prefix ...string)
// Shutdown stops the log service including post-processing and cleanup.
func Shutdown(archivelog bool)
// Startup starts the log service.
func Startup(bufferSize int)
// SetupLog opens and initially creates a log file.
func SetupLog(logName string, appendlog bool)
// SwitchLog closes the current log file and a new log file with the specified name is created and used.
func SwitchLog(newLogName string)
// Write writes a log message to a specified destination.
// Possible destinations are STDOUT, FILE or MULTI (a combination of STDOUT and FILE).
func Write(destination int, values ...any)
// ConditionalWrite writes or doesn't write a log message to a specified destination based on a condition.
func ConditionalWrite(condition bool, destination int, values ...any)
Using the simplelog framework is pretty easy. Firstly, the log service has to be started and initialized by calling the Startup function. Afterwards, the logging can be started by triggering any number of Write function calls. Finally, the log service has to be stopped by calling the Shutdown function. This is important to ensure, the log buffer has been flushed completely and no log message is missing.
Hint:
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The appearance of a log line can be adjusted by specifying prefixes. These prefixes can be defined independently for the standard out logger and the file logger by calling the SetPrefix function. If the prefix should also contain actual date and time data, the Golang reference time placeholders can be applied for given data:
Time Item Placeholder Year 2006 Month 01 Day 02 Hour 15 Minute 04 Second 05 Millisecond 000000 In addition, to distinguish and parse date and time information, the reference time string has to be delimited by the prefix and suffix tag #, for example: #2006-01-02 15:04:05.000000#. Then, all placeholders are replaced at runtime by the logging service accordingly.
Note that not all placeholders have to be used and they can be used in any order.
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The log file used by the log service can be changed by calling the SwitchLog function. Thereby, the current log is closed (not deleted) and a new log file with the specified name is created (a file with the new name must not already exist). The log service does not have to be stopped for this purpose.
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Log files can also be archived automatically when the log service is shut down. In such a case, the closed log file is renamed as follows: <log file name>_yyyymmddHHMMSS, whereas yyyymmddHHMMSS denotes the timestamp when the rename of the log occurred.
Example:
package main
import (
"strconv"
"sync"
"github.com/sabitor/simplelog"
)
func main() {
log1 := "log1.txt"
logBuffer := 2 // number of log messages which can be buffered before the log service blocks
simplelog.Startup(logBuffer)
defer simplelog.Shutdown(false)
simplelog.SetPrefix(simplelog.STDOUT, "STDOUT$")
simplelog.Write(simplelog.STDOUT, ">>> Start application")
simplelog.SetupLog(log1, false)
simplelog.SetPrefix(simplelog.FILE, "#02/01/2023 15:04:05.000000#", "-")
simplelog.Write(simplelog.STDOUT, "Log file is", log1)
simplelog.Write(simplelog.FILE, "[MAIN]", "Write", 1, "to FILE.")
simplelog.Write(simplelog.MULTI, "[MAIN]", "Write", 1, "to MULTI.")
log2 := "log2.txt"
simplelog.SwitchLog(log2)
simplelog.Write(simplelog.STDOUT, "New log file is", log2)
var wg sync.WaitGroup
for i := 1; i <= 4; i++ {
wg.Add(1)
go func(count int) {
defer wg.Done()
context := "[GOROUTINE " + strconv.Itoa(count) + "]"
simplelog.Write(simplelog.FILE, context, "Write", count+1, "to FILE.")
}(i)
}
wg.Wait()
simplelog.Write(simplelog.MULTI, "[MAIN]", "Write", 2, "to MULTI.")
simplelog.Write(simplelog.STDOUT, "<<< Stop application")
}The following log output was generated:
Standard out
STDOUT$ >>> Start application
STDOUT$ Log file is log1.txt
STDOUT$ [MAIN] Write 1 to MULTI.
STDOUT$ New log file is log2.txt
STDOUT$ [MAIN] Write 2 to MULTI.
STDOUT$ <<< Stop application
Log file log1.txt
2023/04/14 08:49:02.555266 - [MAIN] Write 1 to FILE.
2023/04/14 08:49:02.555332 - [MAIN] Write 1 to MULTI.
Log file log2.txt
2023/04/14 08:49:02.555448 - [GOROUTINE 4] Write 5 to FILE.
2023/04/14 08:49:02.555456 - [GOROUTINE 1] Write 2 to FILE.
2023/04/14 08:49:02.555460 - [GOROUTINE 3] Write 4 to FILE.
2023/04/14 08:49:02.555562 - [GOROUTINE 2] Write 3 to FILE.
2023/04/14 08:49:02.555604 - [MAIN] Write 2 to MULTI.