/
event.go
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/
event.go
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package event
import (
"errors"
"fmt"
"sync"
)
var (
// DefaultEvent is the default event and is used by AddHandler, Trigger, AddQueue, Start and Stop.
DefaultEvent = New()
// ErrDone represents that a queue is finished.
ErrDone = errors.New("queue is done")
// ErrNotExist is passed to ErrorHandler if handler not exists.
ErrNotExist = errors.New("handler not exist")
)
// AddHandler is shorthand of the DefaultEvent.AddHandler.
func AddHandler(name string, queueName string, handler func(args ...interface{}) error) error {
return DefaultEvent.AddHandler(name, queueName, handler)
}
// Trigger is shorthand of the DefaultEvent.Trigger.
func Trigger(name string, args ...interface{}) error {
return DefaultEvent.Trigger(name, args...)
}
// RegisterQueue is shorthand of the DefaultEvent.RegisterQueue.
func RegisterQueue(name string, queue Queue) error {
return DefaultEvent.RegisterQueue(name, queue)
}
// Start is shorthand of the DefaultEvent.Start.
func Start() {
DefaultEvent.Start()
}
// Stop is shorthand of the DefaultEvent.Stop.
func Stop() {
DefaultEvent.Stop()
}
// Event represents an Event.
type Event struct {
// ErrorHandler is the error handler.
// If you want to use your own error handler, set ErrorHandler.
ErrorHandler func(err interface{})
workersPerQueue int
queues map[string]Queue
handlerQueues map[string]map[string][]handlerFunc
workers []*worker
wg struct{ enqueue, dequeue sync.WaitGroup }
}
// New returns a new Event.
func New() *Event {
return &Event{
workersPerQueue: 1,
queues: make(map[string]Queue),
handlerQueues: make(map[string]map[string][]handlerFunc),
wg: struct{ enqueue, dequeue sync.WaitGroup }{},
}
}
// AddHandler adds handlers that related to name and queue.
// The name is an event name such as "log.error" that will be used for Trigger.
// The queueName is a name of queue registered by RegisterQueue in advance.
// If you add handler by name that has already been added, handler will associated
// to that name additionally.
// If queue of queueName still hasn't been registered, it returns error.
func (e *Event) AddHandler(name string, queueName string, handler func(args ...interface{}) error) error {
queue := e.queues[queueName]
if queue == nil {
return fmt.Errorf("kocha: event: queue `%s' isn't registered", queueName)
}
if _, exist := e.handlerQueues[name]; !exist {
e.handlerQueues[name] = make(map[string][]handlerFunc)
}
hq := e.handlerQueues[name]
hq[queueName] = append(hq[queueName], handler)
return nil
}
// Trigger emits the event.
// The name is an event name. It must be added in advance using AddHandler.
// If Trigger called by not added name, it returns error.
// If args are given, they will be passed to handlers added by AddHandler.
func (e *Event) Trigger(name string, args ...interface{}) error {
hq, exist := e.handlerQueues[name]
if !exist {
return fmt.Errorf("kocha: event: handler `%s' isn't added", name)
}
e.triggerAll(hq, name, args...)
return nil
}
// RegisterQueue makes a background queue available by the provided name.
// If queue is already registerd or if queue nil, it panics.
func (e *Event) RegisterQueue(name string, queue Queue) error {
if queue == nil {
return fmt.Errorf("kocha: event: Register queue is nil")
}
if _, exist := e.queues[name]; exist {
return fmt.Errorf("kocha: event: Register queue `%s' is already registered", name)
}
e.queues[name] = queue
return nil
}
func (e *Event) triggerAll(hq map[string][]handlerFunc, name string, args ...interface{}) {
e.wg.enqueue.Add(len(hq))
for queueName := range hq {
queue := e.queues[queueName]
go func() {
defer e.wg.enqueue.Done()
defer func() {
if err := recover(); err != nil {
if e.ErrorHandler != nil {
e.ErrorHandler(err)
}
}
}()
if err := e.enqueue(queue, payload{name, args}); err != nil {
panic(err)
}
}()
}
}
// alias.
type handlerFunc func(args ...interface{}) error
func (e *Event) enqueue(queue Queue, pld payload) error {
var data string
if err := pld.encode(&data); err != nil {
return err
}
return queue.Enqueue(data)
}
// Start starts background event workers.
// By default, workers per queue is 1. To set the workers per queue, use
// SetWorkersPerQueue before Start calls.
func (e *Event) Start() {
for name, queue := range e.queues {
for i := 0; i < e.workersPerQueue; i++ {
worker := e.newWorker(name, queue.New(e.workersPerQueue))
e.workers = append(e.workers, worker)
go worker.start()
}
}
}
// SetWorkersPerQueue sets the number of workers per queue.
// It must be called before Start calls.
func (e *Event) SetWorkersPerQueue(n int) {
if n < 1 {
n = 1
}
e.workersPerQueue = n
}
// Stop wait for all workers to complete.
func (e *Event) Stop() {
e.wg.enqueue.Wait()
defer func() {
e.workers = nil
}()
defer e.wg.dequeue.Wait()
for _, worker := range e.workers {
worker.stop()
}
}
type worker struct {
queueName string
queue Queue
e *Event
}
func (e *Event) newWorker(queueName string, queue Queue) *worker {
return &worker{
queueName: queueName,
queue: queue,
e: e,
}
}
func (w *worker) start() {
var done bool
for !done {
func() {
defer func() {
if err := recover(); err != nil {
if w.e.ErrorHandler != nil {
w.e.ErrorHandler(err)
}
}
}()
if err := w.run(); err != nil {
if err == ErrDone {
done = true
return
}
panic(err)
}
}()
}
}
func (w *worker) run() (err error) {
w.e.wg.dequeue.Add(1)
defer w.e.wg.dequeue.Done()
pld, err := w.dequeue()
if err != nil {
return err
}
hq, exist := w.e.handlerQueues[pld.Name]
if !exist {
return ErrNotExist
}
w.runAll(hq, pld)
return nil
}
func (w *worker) runAll(hq map[string][]handlerFunc, pld payload) {
for queueName, handlers := range hq {
if w.queueName != queueName {
continue
}
w.e.wg.dequeue.Add(len(handlers))
for _, h := range handlers {
go func(handler handlerFunc) {
defer w.e.wg.dequeue.Done()
if err := handler(pld.Args...); err != nil {
if w.e.ErrorHandler != nil {
w.e.ErrorHandler(err)
}
}
}(h)
}
}
}
func (w *worker) dequeue() (pld payload, err error) {
data, err := w.queue.Dequeue()
if err != nil {
return pld, err
}
if err := pld.decode(data); err != nil {
return pld, err
}
return pld, nil
}
func (w *worker) stop() {
w.queue.Stop()
}
// Queue is the interface that must be implemeted by background event queue.
type Queue interface {
// New returns a new Queue to launch the workers.
// You can use an argument n as a hint when you create a new queue.
// n is the number of workers per queue.
New(n int) Queue
// Enqueue add data to the queue.
Enqueue(data string) error
// Dequeue returns the data that fetch from the queue.
// It will return ErrDone as err when Stop is called.
Dequeue() (data string, err error)
// Stop wait for Enqueue and/or Dequeue to complete then will stop a queue.
Stop()
}