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main.go
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package tasker
import (
"context"
"database/sql"
"fmt"
"time"
"github.com/kr/pretty"
// Import pq globally
_ "github.com/lib/pq"
"github.com/volatiletech/sqlboiler/boil"
"github.com/volatiletech/sqlboiler/queries/qm"
m "github.com/wesraph/tasker/models"
)
// Typed errors
var (
ErrStepNotFound = fmt.Errorf("step not found")
ErrMissingTaskName = fmt.Errorf("missing task name")
ErrMissingStepName = fmt.Errorf("missing step name")
ErrMissingSteps = fmt.Errorf("missing steps in task")
ErrMissingExecFunction = fmt.Errorf("missing exec function")
ErrReachedMaxRetry = fmt.Errorf("reached max retry for task")
ErrReachedEndOfTask = fmt.Errorf("reached end of task")
ErrNilUserTask = fmt.Errorf("user task is nil")
)
var ctx context.Context
var dbh *sql.DB
// Step is a function to execute
type Step struct {
Name string
Exec func(t *Task) error
}
// Task is a group of steps
type Task struct {
Name string
Steps []Step
UserTask *UserTask
MaxRetry int
}
// UserTask is a user task
type UserTask struct {
Buffer interface{}
Args interface{}
*m.Task
}
// UpdateDB update the task in db
func (u UserTask) UpdateDB() error {
var err error
if u.Buffer != nil {
err = u.UserBuffer.Marshal(u.Buffer)
if err != nil {
return err
}
}
_, err = u.Update(ctx, dbh, boil.Infer())
return err
}
// Scheduler is a group of tasks
type Scheduler struct {
Tasks []Task
}
// Init the database connection and context
func Init(db *sql.DB) {
dbh = db
ctx = context.Background()
}
// Exec execute all tasks in the scheduler
func (s *Scheduler) Exec() error {
fmt.Println("Launching scheduler")
for {
//Get all tasks waiting in db
fmt.Println("Checking new tasks")
todoTasks, err := m.Tasks(qm.Where("todo_date<?", time.Now()), qm.And("status=?", m.TaskStatusTodo)).All(ctx, dbh)
if err != nil {
return err
}
for _, todoTaskDB := range todoTasks {
//Find corresponding task
todoTask := &UserTask{
Task: todoTaskDB,
}
var fnt Task
for _, findNewTask := range s.Tasks {
if findNewTask.Name == todoTask.Name {
fnt = findNewTask
}
}
if fnt.Name == "" {
//TODO:Log error and commit status error
fmt.Println("tasker: task type not found")
continue
}
execTask := fnt
execTask.UserTask = todoTask
err = execTask.Exec()
if err != nil && err == ErrReachedMaxRetry {
//TODO:Log error and commit status error
fmt.Println("Task reached max retry count, setting state error")
execTask.UserTask.Status = m.TaskStatusError
} else if err != nil {
pretty.Println(err)
}
fmt.Println("Update task in DB")
err := execTask.UserTask.UpdateDB()
if err != nil {
return err
}
fmt.Println("Ok")
}
time.Sleep(time.Second)
}
}
// Exec execute at task
func (t *Task) Exec() error {
err := t.initValidate()
if err != nil {
return err
}
actStep, err := t.getActualStep()
for {
err = actStep.Exec(t)
if err != nil {
fmt.Printf("Step %s failed : %s\n", actStep.Name, err.Error())
if t.UserTask.Retry+1 >= t.MaxRetry {
return ErrReachedMaxRetry
}
t.UserTask.Retry++
return nil
}
actStep, err = t.getNextStep()
if err == ErrReachedEndOfTask {
t.UserTask.Status = m.TaskStatusDone
return nil
} else if err != nil {
return err
}
t.UserTask.ActualStep = actStep.Name
err = t.UserTask.UpdateDB()
if err != nil {
return err
}
}
}
func (t *Task) initValidate() error {
if len(t.Steps) == 0 {
return ErrMissingSteps
}
if t.Name == "" {
return ErrMissingTaskName
}
for _, s := range t.Steps {
if s.Name == "" {
return ErrMissingTaskName
}
if s.Exec == nil {
return ErrMissingExecFunction
}
}
if t.UserTask == nil {
return ErrNilUserTask
}
if t.UserTask.ActualStep == "" {
t.UserTask.ActualStep = t.Steps[0].Name
}
if t.UserTask.Status == "" {
t.UserTask.Status = m.TaskStatusTodo
}
return nil
}
func (t *Task) getActualStep() (*Step, error) {
if t.UserTask.ActualStep == "" {
return &t.Steps[0], nil
}
// Find the next step
for _, s := range t.Steps {
if s.Name == t.UserTask.ActualStep {
return &s, nil
}
}
return nil, ErrStepNotFound
}
func (t *Task) getNextStep() (*Step, error) {
if t.UserTask.ActualStep == "" {
return nil, ErrStepNotFound
}
// Find the next step
for i, s := range t.Steps {
if s.Name == t.UserTask.ActualStep {
if i+1 < len(t.Steps) {
return &t.Steps[i+1], nil
}
// No next step, we finished the work
return nil, ErrReachedEndOfTask
}
}
return nil, ErrStepNotFound
}