martin-helmich/prometheus-nginxlog-exporter

package syslog

import (
    "fmt"
    "net/url"
    "os"

    "gopkg.in/mcuadros/go-syslog.v2"
    "gopkg.in/mcuadros/go-syslog.v2/format"
)

func openListener(s *syslog.Server, c string) (func() error, error) {
    u, err := url.Parse(c)
    if err != nil {
        return nil, err
    }

    switch u.Scheme {
    case "tcp":
        return nil, s.ListenTCP(u.Host)

    case "udp":
        return nil, s.ListenUDP(u.Host)

    case "unix":
        socketPath := u.Host + u.Path

        if err := s.ListenUnixgram(socketPath); err != nil {
            return nil, err
        }

        return func() error {
            return os.Remove(socketPath)
        }, nil

    default:
        return nil, fmt.Errorf("syslog server should be in format unix/tcp/udp://127.0.0.1:5533")
    }
}

// Listen opens up a new syslog server on either a TCP or UDP port
func Listen(conn string, formatSpec string) (syslog.LogPartsChannel, *syslog.Server, func() error, error) {
    channel := make(syslog.LogPartsChannel)
    handler := syslog.NewChannelHandler(channel)

    server := syslog.NewServer()

    var format format.Format = syslog.Automatic

    switch formatSpec {
    case "rfc3164":
        format = syslog.RFC3164
    case "rfc5424":
        format = syslog.RFC5424
    case "rfc6587":
        format = syslog.RFC6587
    case "auto":
        format = syslog.Automatic
    case "":
        format = syslog.Automatic
    default:
        return nil, nil, nil, fmt.Errorf("unknown syslog format: '%s'", format)
    }

    //RFC3164 or RFC5424 or RFC6587. nginx works on RFC3164
    server.SetFormat(format)
    server.SetHandler(handler)

    closeListener, err := openListener(server, conn)
    if err != nil {
        return nil, nil, nil, err
    }

    if err = server.Boot(); err != nil {
        return nil, nil, nil, err
    }

    stopFn := func() error {
        if err := server.Kill(); err != nil {
            return fmt.Errorf("failed to kill syslog server: %w", err)
        }

        return closeListener()
    }

    return channel, server, stopFn, nil
}