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worker.go
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worker.go
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package work
import (
"context"
"errors"
"fmt"
"runtime/debug"
"sync"
"time"
"github.com/cenkalti/backoff/v4"
)
// DequeueFunc generates a job.
type DequeueFunc func(*DequeueOptions) (*Job, error)
// DequeueMiddleware modifies DequeueFunc behavior.
type DequeueMiddleware func(DequeueFunc) DequeueFunc
// EnqueueFunc takes in a job for processing.
type EnqueueFunc func(*Job, *EnqueueOptions) error
// EnqueueMiddleware modifies EnqueueFunc behavior.
type EnqueueMiddleware func(EnqueueFunc) EnqueueFunc
// HandleFunc runs a job.
type HandleFunc func(*Job, *DequeueOptions) error
// ContextHandleFunc runs a job.
type ContextHandleFunc func(context.Context, *Job, *DequeueOptions) error
// HandleMiddleware modifies HandleFunc hehavior.
type HandleMiddleware func(HandleFunc) HandleFunc
// BackoffFunc computes when to retry this job from now.
type BackoffFunc func(*Job, *DequeueOptions) time.Duration
type handler struct {
QueueID string
HandleFunc ContextHandleFunc
JobOptions JobOptions
}
// WorkerOptions is used to create a worker.
type WorkerOptions struct {
Namespace string
Queue Queue
ErrorFunc func(error)
}
// Worker runs jobs.
type Worker struct {
opt WorkerOptions
cancel func()
wg sync.WaitGroup
handlerMap map[string]handler
}
// NewWorker creates a new worker.
func NewWorker(opt *WorkerOptions) *Worker {
return &Worker{
opt: *opt,
handlerMap: make(map[string]handler),
}
}
// JobOptions specifies how a job is executed.
type JobOptions struct {
MaxExecutionTime time.Duration
IdleWait time.Duration
NumGoroutines int64
Backoff BackoffFunc
DequeueMiddleware []DequeueMiddleware
HandleMiddleware []HandleMiddleware
}
// options validation error
var (
ErrMaxExecutionTime = errors.New("work: max execution time should be > 0")
ErrNumGoroutines = errors.New("work: number of goroutines should be > 0")
ErrIdleWait = errors.New("work: idle wait should be > 0")
)
// Validate validates JobOptions.
func (opt *JobOptions) Validate() error {
if opt.MaxExecutionTime <= 0 {
return ErrMaxExecutionTime
}
if opt.IdleWait <= 0 {
return ErrIdleWait
}
if opt.NumGoroutines <= 0 {
return ErrNumGoroutines
}
return nil
}
// Register adds handler for a queue.
// queueID and namespace should be the same as the one used to enqueue.
func (w *Worker) Register(queueID string, h HandleFunc, opt *JobOptions) error {
return w.RegisterWithContext(queueID, func(ctx context.Context, job *Job, o *DequeueOptions) error {
return h(job, o)
}, opt)
}
// RegisterWithContext adds handler for a queue with context.Context.
// queueID and namespace should be the same as the one used to enqueue.
// The context is created with context.WithTimeout set from MaxExecutionTime.
func (w *Worker) RegisterWithContext(queueID string, h ContextHandleFunc, opt *JobOptions) error {
err := opt.Validate()
if err != nil {
return err
}
w.handlerMap[queueID] = handler{
QueueID: queueID,
HandleFunc: h,
JobOptions: *opt,
}
return nil
}
// OnceJobOptions specifies how a job is executed.
type OnceJobOptions struct {
MaxExecutionTime time.Duration
Backoff BackoffFunc
DequeueMiddleware []DequeueMiddleware
HandleMiddleware []HandleMiddleware
}
// Validate validates OnceJobOptions.
func (opt *OnceJobOptions) Validate() error {
if opt.MaxExecutionTime <= 0 {
return ErrMaxExecutionTime
}
return nil
}
// RunOnce simply runs one job from a queue.
// The context is created with context.WithTimeout set from MaxExecutionTime.
//
// This is used with kubernetes where a pod is created directly to run a job.
func (w *Worker) RunOnce(ctx context.Context, queueID string, h ContextHandleFunc, opt *OnceJobOptions) error {
err := opt.Validate()
if err != nil {
return err
}
queue := w.opt.Queue
ns := w.opt.Namespace
dequeue := queue.Dequeue
for _, mw := range opt.DequeueMiddleware {
dequeue = mw(dequeue)
}
handle := func(job *Job, o *DequeueOptions) error {
ctx, cancel := context.WithTimeout(ctx, opt.MaxExecutionTime)
defer cancel()
return h(ctx, job, o)
}
for _, mw := range opt.HandleMiddleware {
handle = mw(handle)
}
handle = catchPanic(handle)
b := opt.Backoff
if b == nil {
b = defaultBackoff()
}
handle = retry(queue, b)(handle)
dopt := &DequeueOptions{
Namespace: ns,
QueueID: queueID,
At: time.Now(),
InvisibleSec: int64(opt.MaxExecutionTime / time.Second),
}
job, err := dequeue(dopt)
if err != nil {
return err
}
err = handle(job, dopt)
if err != nil {
return err
}
err = queue.Ack(job, &AckOptions{
Namespace: dopt.Namespace,
QueueID: dopt.QueueID,
})
if err != nil {
return err
}
return nil
}
// Start starts the worker.
func (w *Worker) Start() {
ctx, cancel := context.WithCancel(context.Background())
w.cancel = cancel
for _, h := range w.handlerMap {
for i := int64(0); i < h.JobOptions.NumGoroutines; i++ {
w.wg.Add(1)
go func(h handler) {
defer w.wg.Done()
w.start(ctx, h)
}(h)
}
}
}
func (w *Worker) start(ctx context.Context, h handler) {
// print errors by default so that problems are noticeable.
errFunc := func(err error) { fmt.Println(err) }
if w.opt.ErrorFunc != nil {
errFunc = w.opt.ErrorFunc
}
var dequeueMiddleware []DequeueMiddleware
dequeueMiddleware = append(dequeueMiddleware, h.JobOptions.DequeueMiddleware...)
dequeueMiddleware = append(dequeueMiddleware, idleWait(ctx, h.JobOptions.IdleWait))
var handleMiddleware []HandleMiddleware
handleMiddleware = append(handleMiddleware, h.JobOptions.HandleMiddleware...)
handleMiddleware = append(handleMiddleware, catchPanic, wrapHandlerError)
opt := &OnceJobOptions{
MaxExecutionTime: h.JobOptions.MaxExecutionTime,
Backoff: h.JobOptions.Backoff,
DequeueMiddleware: dequeueMiddleware,
HandleMiddleware: handleMiddleware,
}
for {
select {
case <-ctx.Done():
return
default:
err := w.RunOnce(ctx, h.QueueID, h.HandleFunc, opt)
if err != nil {
var wrappedError *wrappedHandlerError
if errors.As(err, &wrappedError) {
} else if errors.Is(err, ErrEmptyQueue) {
} else {
errFunc(err)
}
}
}
}
}
// ExportMetrics dumps queue stats if the queue implements MetricsExporter.
func (w *Worker) ExportMetrics() (*Metrics, error) {
var queueMetrics []*QueueMetrics
for _, h := range w.handlerMap {
queue := w.opt.Queue
ns := w.opt.Namespace
exporter, ok := queue.(MetricsExporter)
if !ok {
continue
}
m, err := exporter.GetQueueMetrics(&QueueMetricsOptions{
Namespace: ns,
QueueID: h.QueueID,
At: time.Now(),
})
if err != nil {
return nil, err
}
queueMetrics = append(queueMetrics, m)
}
return &Metrics{
Queue: queueMetrics,
}, nil
}
// Stop stops the worker.
func (w *Worker) Stop() {
if w.cancel != nil {
w.cancel()
}
w.wg.Wait()
}
func idleWait(ctx context.Context, d time.Duration) DequeueMiddleware {
return func(f DequeueFunc) DequeueFunc {
return func(opt *DequeueOptions) (*Job, error) {
job, err := f(opt)
if err != nil {
if errors.Is(err, ErrEmptyQueue) {
select {
case <-time.After(d):
case <-ctx.Done():
}
}
return nil, err
}
return job, nil
}
}
}
type wrappedHandlerError struct {
Err error
}
func (e *wrappedHandlerError) Unwrap() error {
return e.Err
}
func (e *wrappedHandlerError) Error() string {
return e.Err.Error()
}
func wrapHandlerError(f HandleFunc) HandleFunc {
return func(job *Job, opt *DequeueOptions) error {
err := f(job, opt)
if err != nil {
return &wrappedHandlerError{Err: err}
}
return nil
}
}
func catchPanic(f HandleFunc) HandleFunc {
return func(job *Job, opt *DequeueOptions) (err error) {
defer func() {
if r := recover(); r != nil {
err = fmt.Errorf("panic: %v\n\n%s", r, debug.Stack())
}
}()
return f(job, opt)
}
}
// retry error
var (
// ErrDoNotRetry is returned if the job should not be retried;
// this may be because the job is unrecoverable, or because
// the handler has already rescheduled it.
ErrDoNotRetry = errors.New("work: do not retry")
// ErrUnrecoverable is returned if the error is unrecoverable.
// The job will be discarded.
ErrUnrecoverable = fmt.Errorf("work: permanent error: %w", ErrDoNotRetry)
)
// https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md
func defaultBackoff() BackoffFunc {
return func(job *Job, opt *DequeueOptions) time.Duration {
b := backoff.NewExponentialBackOff()
b.InitialInterval = 2 * time.Second
b.RandomizationFactor = 0.2
b.Multiplier = 1.6
b.MaxInterval = 24 * time.Hour
b.MaxElapsedTime = 0
b.Reset()
var next time.Duration
for i := int64(0); i < job.Retries; i++ {
next = b.NextBackOff()
}
return next
}
}
func retry(queue Queue, backoff BackoffFunc) HandleMiddleware {
return func(f HandleFunc) HandleFunc {
return func(job *Job, opt *DequeueOptions) error {
err := f(job, opt)
if err != nil {
if errors.Is(err, ErrUnrecoverable) {
return nil // ack
}
if errors.Is(err, ErrDoNotRetry) {
// don't ack and don't reenqueue
return err
}
now := time.Now()
job.Retries++
job.LastError = err.Error()
job.UpdatedAt = now
job.EnqueuedAt = now.Add(backoff(job, opt))
queue.Enqueue(job, &EnqueueOptions{
Namespace: opt.Namespace,
QueueID: opt.QueueID,
})
return err
}
return nil
}
}
}