From 55261a2b155c4e3d699fc6bd4255f05fb8258157 Mon Sep 17 00:00:00 2001
From: Chris <ccbrown112@gmail.com>
Date: Fri, 23 Feb 2018 12:56:32 -0600
Subject: fix scheduled task race (#8355)

---
 model/scheduled_task.go | 97 ++++++++++++++++---------------------------------
 1 file changed, 32 insertions(+), 65 deletions(-)

(limited to 'model/scheduled_task.go')

diff --git a/model/scheduled_task.go b/model/scheduled_task.go
index 453828bd2..f3529dedb 100644
--- a/model/scheduled_task.go
+++ b/model/scheduled_task.go
@@ -5,7 +5,6 @@ package model
 
 import (
 	"fmt"
-	"sync"
 	"time"
 )
 
@@ -15,89 +14,57 @@ type ScheduledTask struct {
 	Name      string        `json:"name"`
 	Interval  time.Duration `json:"interval"`
 	Recurring bool          `json:"recurring"`
-	function  TaskFunc
-	timer     *time.Timer
-}
-
-var taskMutex = sync.Mutex{}
-var tasks = make(map[string]*ScheduledTask)
-
-func addTask(task *ScheduledTask) {
-	taskMutex.Lock()
-	defer taskMutex.Unlock()
-	tasks[task.Name] = task
-}
-
-func removeTaskByName(name string) {
-	taskMutex.Lock()
-	defer taskMutex.Unlock()
-	delete(tasks, name)
-}
-
-func GetTaskByName(name string) *ScheduledTask {
-	taskMutex.Lock()
-	defer taskMutex.Unlock()
-	if task, ok := tasks[name]; ok {
-		return task
-	}
-	return nil
-}
-
-func GetAllTasks() *map[string]*ScheduledTask {
-	taskMutex.Lock()
-	defer taskMutex.Unlock()
-	return &tasks
+	function  func()
+	cancel    chan struct{}
+	cancelled chan struct{}
 }
 
 func CreateTask(name string, function TaskFunc, timeToExecution time.Duration) *ScheduledTask {
-	task := &ScheduledTask{
-		Name:      name,
-		Interval:  timeToExecution,
-		Recurring: false,
-		function:  function,
-	}
-
-	taskRunner := func() {
-		go task.function()
-		removeTaskByName(task.Name)
-	}
-
-	task.timer = time.AfterFunc(timeToExecution, taskRunner)
-
-	addTask(task)
-
-	return task
+	return createTask(name, function, timeToExecution, false)
 }
 
 func CreateRecurringTask(name string, function TaskFunc, interval time.Duration) *ScheduledTask {
+	return createTask(name, function, interval, true)
+}
+
+func createTask(name string, function TaskFunc, interval time.Duration, recurring bool) *ScheduledTask {
 	task := &ScheduledTask{
 		Name:      name,
 		Interval:  interval,
-		Recurring: true,
+		Recurring: recurring,
 		function:  function,
+		cancel:    make(chan struct{}),
+		cancelled: make(chan struct{}),
 	}
 
-	taskRecurer := func() {
-		go task.function()
-		task.timer.Reset(task.Interval)
-	}
+	go func() {
+		defer close(task.cancelled)
 
-	task.timer = time.AfterFunc(interval, taskRecurer)
+		ticker := time.NewTicker(interval)
+		defer func() {
+			ticker.Stop()
+		}()
 
-	addTask(task)
+		for {
+			select {
+			case <-ticker.C:
+				function()
+			case <-task.cancel:
+				return
+			}
+
+			if !task.Recurring {
+				break
+			}
+		}
+	}()
 
 	return task
 }
 
 func (task *ScheduledTask) Cancel() {
-	task.timer.Stop()
-	removeTaskByName(task.Name)
-}
-
-// Executes the task immediatly. A recurring task will be run regularally after interval.
-func (task *ScheduledTask) Execute() {
-	task.function()
-	task.timer.Reset(task.Interval)
+	close(task.cancel)
+	<-task.cancelled
 }
 
 func (task *ScheduledTask) String() string {
-- 
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