Golang windows service not writting to logfile - go

Question

I have a simple TCP-server written in Go and running as windows service. It installs/uninstalls just fine, it is working as service and doing it's job but it's not writing a single word in a log file. When I run it simply as an executable in a console - logging works fine. But when it starts as a service - log file is created, application process opens it (thus disallowing to delete it for example) but file remains empty. What I'm doing wrong?
Any word of advice is appreciated.
logging is confured like this
func (p *Program) run() {
exec, _ := os.Executable()
WORK_DIR = filepath.Join(filepath.Dir(exec), "ATT")
_, err := checkDir(WORK_DIR)
if err != nil {
panic("Не удалось создать рабочий каталог")
}
f, err := os.OpenFile(filepath.Join(filepath.Dir(exec), "server.log"), os.O_RDWR|os.O_CREATE|os.O_APPEND, 0666)
if err != nil {
log.Fatalf("Не удалось создать лог-файл: %v", err)
}
defer f.Close()
wrt := io.MultiWriter(os.Stdout, f)
log.SetOutput(wrt)
server, err := net.Listen("tcp", ":"+PORT)
if err != nil {
log.Fatal(err)
}
defer server.Close()
log.Println("Сервер запущен на порту:", PORT)
for {
connection, err := server.Accept()
if err != nil {
log.Println("Не удалось установить соединение с клиентом", err)
}
go HandleServer(connection)
}
}

Answer 1

The issue you're encountering with logging can be related to file permissions when running as a service. When a service starts, it runs with a different set of permissions than when it runs as a regular executable. In some cases, the service might not have permission to write to a log file in the same location as the executable.
One possible solution is to specify a different location for the log file, such as C:\Windows\System32\LogFiles, which is a common location for log files in Windows. You could also try specifying the absolute path to the log file in the OpenFile call to avoid any confusion about the working directory.
Another potential issue could be with the defer statement that closes the log file. When the service terminates, any deferred statements will be executed, which could cause the log file to be closed before all log messages have been written. To avoid this, you could remove the defer statement and manually close the log file when the service stops.
It may also be a good idea to add error handling to the logging calls to ensure that all log messages are being written even if the log file becomes unavailable. Here is an example:
func (p *Program) run() {
exec, _ := os.Executable()
WORK_DIR = filepath.Join(filepath.Dir(exec), "ATT")
_, err := checkDir(WORK_DIR)
if err != nil {
panic("Не удалось создать рабочий каталог")
}
// Specify the absolute path for the log file
logFilePath := filepath.Join(filepath.Dir(exec), "server.log")
f, err := os.OpenFile(logFilePath, os.O_RDWR|os.O_CREATE|os.O_APPEND, 0666)
if err != nil {
log.Fatalf("Не удалось создать лог-файл: %v", err)
}
// Remove the defer statement to close the log file manually later
// defer f.Close()
wrt := io.MultiWriter(os.Stdout, f)
log.SetOutput(wrt)
server, err := net.Listen("tcp", ":"+PORT)
if err != nil {
log.Fatal(err)
}
defer server.Close()
log.Println("Сервер запущен на порту:", PORT)
for {
connection, err := server.Accept()
if err != nil {
log.Println("Не удалось установить соединение с клиентом", err)
}
go HandleServer(connection)
}
// Manually close the log file when the service stops
f.Close()
}
// Add error handling to the logging calls
func logMessage(message string) {
_, logErr := log.Println(message)
if logErr != nil {
fmt.Printf("Error logging message: %v\n", logErr)
}
}
I hope these suggestions help you resolve the issue with logging in your service. Please let me know.