From 3d1341ce2c22580f905a6422decdffc688ffbb08 Mon Sep 17 00:00:00 2001
From: Aditya Mukerjee <dev@chimeracoder.net>
Date: Fri, 4 Aug 2017 11:24:22 -0400
Subject: [PATCH 1/4] Add AddHook method for logger

---
 logger.go | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/logger.go b/logger.go
index 2acab05..fdaf8a6 100644
--- a/logger.go
+++ b/logger.go
@@ -315,3 +315,9 @@ func (logger *Logger) level() Level {
 func (logger *Logger) SetLevel(level Level) {
 	atomic.StoreUint32((*uint32)(&logger.Level), uint32(level))
 }
+
+func (logger *Logger) AddHook(hook Hook) {
+	logger.mu.Lock()
+	defer logger.mu.Unlock()
+	logger.Hooks.Add(hook)
+}

From 66230b287179d93b8a9ca65d5e08495b24163535 Mon Sep 17 00:00:00 2001
From: Aditya Mukerjee <dev@chimeracoder.net>
Date: Fri, 4 Aug 2017 13:00:10 -0400
Subject: [PATCH 2/4] Add test for race condition in hooks

---
 hook_test.go | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/hook_test.go b/hook_test.go
index 13f34cb..d14d1e3 100644
--- a/hook_test.go
+++ b/hook_test.go
@@ -1,6 +1,7 @@
 package logrus
 
 import (
+	"sync"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -120,3 +121,22 @@ func TestErrorHookShouldFireOnError(t *testing.T) {
 		assert.Equal(t, hook.Fired, true)
 	})
 }
+
+func TestAddHookRace(t *testing.T) {
+	var wg sync.WaitGroup
+	wg.Add(2)
+	hook := new(ErrorHook)
+	LogAndAssertJSON(t, func(log *Logger) {
+		go func() {
+			defer wg.Done()
+			log.AddHook(hook)
+		}()
+		go func() {
+			defer wg.Done()
+			log.Error("test")
+		}()
+		wg.Wait()
+	}, func(fields Fields) {
+		assert.Equal(t, hook.Fired, true)
+	})
+}

From c830992a61feb7c379da5708645b44cf27041a02 Mon Sep 17 00:00:00 2001
From: Aditya Mukerjee <dev@chimeracoder.net>
Date: Fri, 4 Aug 2017 13:00:43 -0400
Subject: [PATCH 3/4] Take lock on mutex when firing hooks

---
 entry.go | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/entry.go b/entry.go
index 5bf582e..1fad45e 100644
--- a/entry.go
+++ b/entry.go
@@ -94,7 +94,10 @@ func (entry Entry) log(level Level, msg string) {
 	entry.Level = level
 	entry.Message = msg
 
-	if err := entry.Logger.Hooks.Fire(level, &entry); err != nil {
+	entry.Logger.mu.Lock()
+	err := entry.Logger.Hooks.Fire(level, &entry)
+	entry.Logger.mu.Unlock()
+	if err != nil {
 		entry.Logger.mu.Lock()
 		fmt.Fprintf(os.Stderr, "Failed to fire hook: %v\n", err)
 		entry.Logger.mu.Unlock()

From 9bc52e39813590fd3b61e23badfc85c3bbee2a73 Mon Sep 17 00:00:00 2001
From: Aditya Mukerjee <dev@chimeracoder.net>
Date: Fri, 4 Aug 2017 13:01:04 -0400
Subject: [PATCH 4/4] Fix test assertion

---
 hook_test.go | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/hook_test.go b/hook_test.go
index d14d1e3..4fea751 100644
--- a/hook_test.go
+++ b/hook_test.go
@@ -137,6 +137,8 @@ func TestAddHookRace(t *testing.T) {
 		}()
 		wg.Wait()
 	}, func(fields Fields) {
-		assert.Equal(t, hook.Fired, true)
+		// the line may have been logged
+		// before the hook was added, so we can't
+		// actually assert on the hook
 	})
 }