From f160b155bbf102560c81fff57775175ebaa34441 Mon Sep 17 00:00:00 2001
From: aluvare <luvare@gmail.com>
Date: Thu, 11 Feb 2021 15:56:16 +0100
Subject: [PATCH] The syslog library has been changed to prevent crashes if the
 syslog server is down, writing does not degrade if syslog server is slow.

---
 hooks/syslog/syslog.go | 89 +++++++++++++++++++++++++++++++-----------
 1 file changed, 67 insertions(+), 22 deletions(-)

diff --git a/hooks/syslog/syslog.go b/hooks/syslog/syslog.go
index 02b8df3..0d75516 100644
--- a/hooks/syslog/syslog.go
+++ b/hooks/syslog/syslog.go
@@ -4,50 +4,95 @@ package syslog
 
 import (
 	"fmt"
-	"log/syslog"
+	//"log/syslog"
+	"github.com/GolangResources/syslog/syslog"
 	"os"
+	"time"
 
 	"github.com/sirupsen/logrus"
 )
 
+const (
+	NUM_SYSLOG_WORKERS = 8
+	CHANNEL_DEPTH = 8192
+)
+
 // SyslogHook to send logs via syslog.
 type SyslogHook struct {
-	Writer        *syslog.Writer
-	SyslogNetwork string
-	SyslogRaddr   string
+	Writer		*syslog.Writer
+	SyslogNetwork	string
+	SyslogRaddr	string
+	Tag		string
+	syschan		chan *SEntry
+}
+
+type SEntry struct {
+	line		string
+	level		logrus.Level
 }
 
 // Creates a hook to be added to an instance of logger. This is called with
 // `hook, err := NewSyslogHook("udp", "localhost:514", syslog.LOG_DEBUG, "")`
 // `if err == nil { log.Hooks.Add(hook) }`
 func NewSyslogHook(network, raddr string, priority syslog.Priority, tag string) (*SyslogHook, error) {
-	w, err := syslog.Dial(network, raddr, priority, tag)
-	return &SyslogHook{w, network, raddr}, err
+	w, err := syslog.Dial("ctcp" , raddr, priority, nil)
+	if err != nil {
+		return nil, err
+	}
+	hook := &SyslogHook{
+		w,
+		network,
+		raddr,
+		tag,
+		make(chan *SEntry, CHANNEL_DEPTH),
+	}
+	for i := 0; i <= NUM_SYSLOG_WORKERS; i++ {
+		go hook.worker(i)
+	}
+	return hook, err
+}
+
+func (hook *SyslogHook) worker(i int) {
+	for entry := range hook.syschan {
+		time.Sleep(1)
+		func() error {
+			switch entry.level {
+			case logrus.PanicLevel:
+				return hook.Writer.Crit(&entry.line, hook.Tag)
+			case logrus.FatalLevel:
+				return hook.Writer.Crit(&entry.line, hook.Tag)
+			case logrus.ErrorLevel:
+				return hook.Writer.Err(&entry.line, hook.Tag)
+			case logrus.WarnLevel:
+				return hook.Writer.Warning(&entry.line, hook.Tag)
+			case logrus.InfoLevel:
+				return hook.Writer.Info(&entry.line, hook.Tag)
+			case logrus.DebugLevel, logrus.TraceLevel:
+				return hook.Writer.Debug(&entry.line, hook.Tag)
+			default:
+				return nil
+			}
+		}()
+	}
 }
 
 func (hook *SyslogHook) Fire(entry *logrus.Entry) error {
+	var err error
 	line, err := entry.String()
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "Unable to read entry, %v", err)
 		return err
 	}
-
-	switch entry.Level {
-	case logrus.PanicLevel:
-		return hook.Writer.Crit(line)
-	case logrus.FatalLevel:
-		return hook.Writer.Crit(line)
-	case logrus.ErrorLevel:
-		return hook.Writer.Err(line)
-	case logrus.WarnLevel:
-		return hook.Writer.Warning(line)
-	case logrus.InfoLevel:
-		return hook.Writer.Info(line)
-	case logrus.DebugLevel, logrus.TraceLevel:
-		return hook.Writer.Debug(line)
-	default:
-		return nil
+	sentry := &SEntry{
+		line:	line,
+		level:	entry.Level,
 	}
+	select {
+	case hook.syschan <- sentry:
+	default:
+		err = fmt.Errorf("logrus syslog chan full")
+	}
+	return err
 }
 
 func (hook *SyslogHook) Levels() []logrus.Level {