slogemail

slogemail

Go's log/slog email handler. Wraps slog's JSONHandler or TextHander. There are three ways to create a handler.

Synchronous handler

Behaves as a regular handler but also send an email. By default, email subject is log level and body is log message rendered by base handler. This can be customized by setting GetSubject and GetBody in slogemail.EmailHandlerOpts.

h, err := slogemail.NewHandler(
	os.Stdout, 
	&slog.HandlerOptions{AddSource: true, Level: slog.LevelDebug}, 
	slogemail.EmailHandlerOpts{
                FromAddr:       "from@example.com",
                ToAddrs:        []string{"one@example.com", "two@example.com"},
                JSON:           true,
                // Level can be different from base handler options
                Level:          slog.LevelError, 
                ConnectionInfo: slogemail.SMTPConnectionInfo{
                        Host:     "example.com",
                        Port:     587,
                        Username: "user",
                        Password: "pwd",
                },
        })
if err != nil {
		panic(err)
}

logger := slog.New(h)
// will printed to stdout and sent to email
logger.Error("database error", "detail", "database has gone away")
// will only be printed
logger.Info("login", "user", os.Getenv("USER"))

Asynchronous handler

The same as synchronous, but sending email is performed in a separate goroutine, so that log handling takes less time for the calling goroutine. The handler should be explicitly stopped by calling a provided function, otherwise some log records may be lost.

h, stop, err := slogemail.NewAsyncHandler(
	os.Stdout, 
	&slog.HandlerOptions{AddSource: true, Level: slog.LevelDebug}, 
	slogemail.EmailHandlerOpts{				
				// how many log records can be sent to handler before it starts to process them synchronously
				AsyncQueueSize: 10,
                FromAddr:       "from@example.com",
                ToAddrs:        []string{"one@example.com", "two@example.com"},
                JSON:           true,
                Level:          slog.LevelError, 
                ConnectionInfo: slogemail.SMTPConnectionInfo{
                        Host:     "example.com",
                        Port:     587,
                        Username: "user",
                        Password: "pwd",
                },
        })
if err != nil {
		panic(err)
}

// Needs to be called before application exits so that handler can process remaining logs
defer stop()

logger := slog.New(h)
// will printed to stdout and sent to email
logger.Error("just awful", "err", "database error")
// will only be printed
logger.Info("hello, world", "user", os.Getenv("USER"))

Custom synchronous handler

User defines a function that will handle log record.

h := slogemail.NewCustomHandler(
		os.Stdout,
		&slog.HandlerOptions{Level: slog.LevelDebug},
		func(ctx context.Context, r slog.Record, logOutput string) error {
				doSomething(ctx, logOutput)
		},
		true)

logger := slog.New(h)