Add IsFailure to Config

With this IsFailure config, users can provide a predicate function to 
determine whether the error returned from Handler counts as a failure.

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- `IsFailure` config option is added to determine whether error returned from Handler counts as a failure.
+
 ## [0.18.4] - 2020-08-17
 
 ### Fixed

internal/base/base.go

@@ -645,7 +645,7 @@ type Broker interface {
 	Requeue(msg *TaskMessage) error
 	Schedule(msg *TaskMessage, processAt time.Time) error
 	ScheduleUnique(msg *TaskMessage, processAt time.Time, ttl time.Duration) error
-	Retry(msg *TaskMessage, processAt time.Time, errMsg string) error
+	Retry(msg *TaskMessage, processAt time.Time, errMsg string, isFailure bool) error
 	Archive(msg *TaskMessage, errMsg string) error
 	ForwardIfReady(qnames ...string) error
 	ListDeadlineExceeded(deadline time.Time, qnames ...string) ([]*TaskMessage, error)

internal/rdb/benchmark_test.go

@@ -184,7 +184,7 @@ func BenchmarkRetry(b *testing.B) {
 		asynqtest.SeedDeadlines(b, r.client, zs, base.DefaultQueueName)
 		b.StartTimer()
 
-		if err := r.Retry(msgs[0], time.Now().Add(1*time.Minute), "error"); err != nil {
+		if err := r.Retry(msgs[0], time.Now().Add(1*time.Minute), "error", true /*isFailure*/); err != nil {
 			b.Fatalf("Retry failed: %v", err)
 		}
 	}

internal/rdb/rdb.go

@@ -467,6 +467,7 @@ func (r *RDB) ScheduleUnique(msg *base.TaskMessage, processAt time.Time, ttl tim
 // ARGV[2] -> updated base.TaskMessage value
 // ARGV[3] -> retry_at UNIX timestamp
 // ARGV[4] -> stats expiration timestamp
+// ARGV[5] -> is_failure (bool)
 var retryCmd = redis.NewScript(`
 if redis.call("LREM", KEYS[2], 0, ARGV[1]) == 0 then
   return redis.error_reply("NOT FOUND")
@@ -476,6 +477,7 @@ if redis.call("ZREM", KEYS[3], ARGV[1]) == 0 then
 end
 redis.call("ZADD", KEYS[4], ARGV[3], ARGV[1])
 redis.call("HSET", KEYS[1], "msg", ARGV[2], "state", "retry")
+if tonumber(ARGV[5]) == 1 then
 	local n = redis.call("INCR", KEYS[5])
 	if tonumber(n) == 1 then
 		redis.call("EXPIREAT", KEYS[5], ARGV[4])
@@ -484,15 +486,19 @@ local m = redis.call("INCR", KEYS[6])
 	if tonumber(m) == 1 then
 		redis.call("EXPIREAT", KEYS[6], ARGV[4])
 	end
+end
 return redis.status_reply("OK")`)
 
-// Retry moves the task from active to retry queue, incrementing retry count
+// Retry moves the task from active to retry queue.
-// and assigning error message to the task message.
+// It also annotates the message with the given error message and
-func (r *RDB) Retry(msg *base.TaskMessage, processAt time.Time, errMsg string) error {
+// if isFailure is true increments the retried counter.
+func (r *RDB) Retry(msg *base.TaskMessage, processAt time.Time, errMsg string, isFailure bool) error {
 	var op errors.Op = "rdb.Retry"
 	now := time.Now()
 	modified := *msg
+	if isFailure {
 		modified.Retried++
+	}
 	modified.ErrorMsg = errMsg
 	modified.LastFailedAt = now.Unix()
 	encoded, err := base.EncodeMessage(&modified)
@@ -513,6 +519,7 @@ func (r *RDB) Retry(msg *base.TaskMessage, processAt time.Time, errMsg string) e
 		encoded,
 		processAt.Unix(),
 		expireAt.Unix(),
+		isFailure,
 	}
 	return r.runScript(op, retryCmd, keys, argv...)
 }

internal/rdb/rdb_test.go

@@ -1158,7 +1158,7 @@ func TestRetry(t *testing.T) {
 		h.SeedAllRetryQueues(t, r.client, tc.retry)
 
 		callTime := time.Now() // time when method was called
-		err := r.Retry(tc.msg, tc.processAt, tc.errMsg)
+		err := r.Retry(tc.msg, tc.processAt, tc.errMsg, true /*isFailure*/)
 		if err != nil {
 			t.Errorf("(*RDB).Retry = %v, want nil", err)
 			continue
@@ -1210,6 +1210,173 @@ func TestRetry(t *testing.T) {
 	}
 }
 
+func TestRetryWithNonFailureError(t *testing.T) {
+	r := setup(t)
+	defer r.Close()
+	now := time.Now()
+	t1 := &base.TaskMessage{
+		ID:      uuid.New(),
+		Type:    "send_email",
+		Payload: h.JSON(map[string]interface{}{"subject": "Hola!"}),
+		Retried: 10,
+		Timeout: 1800,
+		Queue:   "default",
+	}
+	t2 := &base.TaskMessage{
+		ID:      uuid.New(),
+		Type:    "gen_thumbnail",
+		Payload: h.JSON(map[string]interface{}{"path": "some/path/to/image.jpg"}),
+		Timeout: 3000,
+		Queue:   "default",
+	}
+	t3 := &base.TaskMessage{
+		ID:      uuid.New(),
+		Type:    "reindex",
+		Payload: nil,
+		Timeout: 60,
+		Queue:   "default",
+	}
+	t4 := &base.TaskMessage{
+		ID:      uuid.New(),
+		Type:    "send_notification",
+		Payload: nil,
+		Timeout: 1800,
+		Queue:   "custom",
+	}
+	t1Deadline := now.Unix() + t1.Timeout
+	t2Deadline := now.Unix() + t2.Timeout
+	t4Deadline := now.Unix() + t4.Timeout
+	errMsg := "SMTP server is not responding"
+
+	tests := []struct {
+		active        map[string][]*base.TaskMessage
+		deadlines     map[string][]base.Z
+		retry         map[string][]base.Z
+		msg           *base.TaskMessage
+		processAt     time.Time
+		errMsg        string
+		wantActive    map[string][]*base.TaskMessage
+		wantDeadlines map[string][]base.Z
+		getWantRetry  func(failedAt time.Time) map[string][]base.Z
+	}{
+		{
+			active: map[string][]*base.TaskMessage{
+				"default": {t1, t2},
+			},
+			deadlines: map[string][]base.Z{
+				"default": {{Message: t1, Score: t1Deadline}, {Message: t2, Score: t2Deadline}},
+			},
+			retry: map[string][]base.Z{
+				"default": {{Message: t3, Score: now.Add(time.Minute).Unix()}},
+			},
+			msg:       t1,
+			processAt: now.Add(5 * time.Minute),
+			errMsg:    errMsg,
+			wantActive: map[string][]*base.TaskMessage{
+				"default": {t2},
+			},
+			wantDeadlines: map[string][]base.Z{
+				"default": {{Message: t2, Score: t2Deadline}},
+			},
+			getWantRetry: func(failedAt time.Time) map[string][]base.Z {
+				return map[string][]base.Z{
+					"default": {
+						// Task message should include the error message but without incrementing the retry count.
+						{Message: h.TaskMessageWithError(*t1, errMsg, failedAt), Score: now.Add(5 * time.Minute).Unix()},
+						{Message: t3, Score: now.Add(time.Minute).Unix()},
+					},
+				}
+			},
+		},
+		{
+			active: map[string][]*base.TaskMessage{
+				"default": {t1, t2},
+				"custom":  {t4},
+			},
+			deadlines: map[string][]base.Z{
+				"default": {{Message: t1, Score: t1Deadline}, {Message: t2, Score: t2Deadline}},
+				"custom":  {{Message: t4, Score: t4Deadline}},
+			},
+			retry: map[string][]base.Z{
+				"default": {},
+				"custom":  {},
+			},
+			msg:       t4,
+			processAt: now.Add(5 * time.Minute),
+			errMsg:    errMsg,
+			wantActive: map[string][]*base.TaskMessage{
+				"default": {t1, t2},
+				"custom":  {},
+			},
+			wantDeadlines: map[string][]base.Z{
+				"default": {{Message: t1, Score: t1Deadline}, {Message: t2, Score: t2Deadline}},
+				"custom":  {},
+			},
+			getWantRetry: func(failedAt time.Time) map[string][]base.Z {
+				return map[string][]base.Z{
+					"default": {},
+					"custom": {
+						// Task message should include the error message but without incrementing the retry count.
+						{Message: h.TaskMessageWithError(*t4, errMsg, failedAt), Score: now.Add(5 * time.Minute).Unix()},
+					},
+				}
+			},
+		},
+	}
+
+	for _, tc := range tests {
+		h.FlushDB(t, r.client)
+		h.SeedAllActiveQueues(t, r.client, tc.active)
+		h.SeedAllDeadlines(t, r.client, tc.deadlines)
+		h.SeedAllRetryQueues(t, r.client, tc.retry)
+
+		callTime := time.Now() // time when method was called
+		err := r.Retry(tc.msg, tc.processAt, tc.errMsg, false /*isFailure*/)
+		if err != nil {
+			t.Errorf("(*RDB).Retry = %v, want nil", err)
+			continue
+		}
+
+		for queue, want := range tc.wantActive {
+			gotActive := h.GetActiveMessages(t, r.client, queue)
+			if diff := cmp.Diff(want, gotActive, h.SortMsgOpt); diff != "" {
+				t.Errorf("mismatch found in %q; (-want, +got)\n%s", base.ActiveKey(queue), diff)
+			}
+		}
+		for queue, want := range tc.wantDeadlines {
+			gotDeadlines := h.GetDeadlinesEntries(t, r.client, queue)
+			if diff := cmp.Diff(want, gotDeadlines, h.SortZSetEntryOpt); diff != "" {
+				t.Errorf("mismatch found in %q; (-want, +got)\n%s", base.DeadlinesKey(queue), diff)
+			}
+		}
+		cmpOpts := []cmp.Option{
+			h.SortZSetEntryOpt,
+			cmpopts.EquateApproxTime(5 * time.Second), // for LastFailedAt field
+		}
+		wantRetry := tc.getWantRetry(callTime)
+		for queue, want := range wantRetry {
+			gotRetry := h.GetRetryEntries(t, r.client, queue)
+			if diff := cmp.Diff(want, gotRetry, cmpOpts...); diff != "" {
+				t.Errorf("mismatch found in %q; (-want, +got)\n%s", base.RetryKey(queue), diff)
+			}
+		}
+
+		// If isFailure is set to false, no stats should be recorded to avoid skewing the error rate.
+		processedKey := base.ProcessedKey(tc.msg.Queue, time.Now())
+		gotProcessed := r.client.Get(processedKey).Val()
+		if gotProcessed != "" {
+			t.Errorf("GET %q = %q, want empty", processedKey, gotProcessed)
+		}
+
+		// If isFailure is set to false, no stats should be recorded to avoid skewing the error rate.
+		failedKey := base.FailedKey(tc.msg.Queue, time.Now())
+		gotFailed := r.client.Get(failedKey).Val()
+		if gotFailed != "" {
+			t.Errorf("GET %q = %q, want empty", failedKey, gotFailed)
+		}
+	}
+}
+
 func TestArchive(t *testing.T) {
 	r := setup(t)
 	defer r.Close()

internal/testbroker/testbroker.go

@@ -108,13 +108,13 @@ func (tb *TestBroker) ScheduleUnique(msg *base.TaskMessage, processAt time.Time,
 	return tb.real.ScheduleUnique(msg, processAt, ttl)
 }
 
-func (tb *TestBroker) Retry(msg *base.TaskMessage, processAt time.Time, errMsg string) error {
+func (tb *TestBroker) Retry(msg *base.TaskMessage, processAt time.Time, errMsg string, isFailure bool) error {
 	tb.mu.Lock()
 	defer tb.mu.Unlock()
 	if tb.sleeping {
 		return errRedisDown
 	}
-	return tb.real.Retry(msg, processAt, errMsg)
+	return tb.real.Retry(msg, processAt, errMsg, isFailure)
 }
 
 func (tb *TestBroker) Archive(msg *base.TaskMessage, errMsg string) error {

processor.go

@@ -33,6 +33,7 @@ type processor struct {
 	orderedQueues []string
 
 	retryDelayFunc RetryDelayFunc
+	isFailureFunc  func(error) bool
 
 	errHandler ErrorHandler
 
@@ -70,6 +71,7 @@ type processorParams struct {
 	logger          *log.Logger
 	broker          base.Broker
 	retryDelayFunc  RetryDelayFunc
+	isFailureFunc   func(error) bool
 	syncCh          chan<- *syncRequest
 	cancelations    *base.Cancelations
 	concurrency     int
@@ -94,6 +96,7 @@ func newProcessor(params processorParams) *processor {
 		queueConfig:     queues,
 		orderedQueues:   orderedQueues,
 		retryDelayFunc:  params.retryDelayFunc,
+		isFailureFunc:   params.isFailureFunc,
 		syncRequestCh:   params.syncCh,
 		cancelations:    params.cancelations,
 		errLogLimiter:   rate.NewLimiter(rate.Every(3*time.Second), 1),
@@ -197,7 +200,7 @@ func (p *processor) exec() {
 			select {
 			case <-ctx.Done():
 				// already canceled (e.g. deadline exceeded).
-				p.retryOrKill(ctx, msg, ctx.Err())
+				p.retryOrArchive(ctx, msg, ctx.Err())
 				return
 			default:
 			}
@@ -214,7 +217,7 @@ func (p *processor) exec() {
 				p.requeue(msg)
 				return
 			case <-ctx.Done():
-				p.retryOrKill(ctx, msg, ctx.Err())
+				p.retryOrArchive(ctx, msg, ctx.Err())
 				return
 			case resErr := <-resCh:
 				// Note: One of three things should happen.
@@ -222,7 +225,7 @@ func (p *processor) exec() {
 				// 2) Retry    -> Removes the message from Active & Adds the message to Retry
 				// 3) Archive  -> Removes the message from Active & Adds the message to archive
 				if resErr != nil {
-					p.retryOrKill(ctx, msg, resErr)
+					p.retryOrArchive(ctx, msg, resErr)
 					return
 				}
 				p.markAsDone(ctx, msg)
@@ -263,22 +266,27 @@ func (p *processor) markAsDone(ctx context.Context, msg *base.TaskMessage) {
 // the task should not be retried and should be archived instead.
 var SkipRetry = errors.New("skip retry for the task")
 
-func (p *processor) retryOrKill(ctx context.Context, msg *base.TaskMessage, err error) {
+func (p *processor) retryOrArchive(ctx context.Context, msg *base.TaskMessage, err error) {
 	if p.errHandler != nil {
 		p.errHandler.HandleError(ctx, NewTask(msg.Type, msg.Payload), err)
 	}
+	if !p.isFailureFunc(err) {
+		// retry the task without marking it as failed
+		p.retry(ctx, msg, err, false /*isFailure*/)
+		return
+	}
 	if msg.Retried >= msg.Retry || errors.Is(err, SkipRetry) {
 		p.logger.Warnf("Retry exhausted for task id=%s", msg.ID)
 		p.archive(ctx, msg, err)
 	} else {
-		p.retry(ctx, msg, err)
+		p.retry(ctx, msg, err, true /*isFailure*/)
 	}
 }
 
-func (p *processor) retry(ctx context.Context, msg *base.TaskMessage, e error) {
+func (p *processor) retry(ctx context.Context, msg *base.TaskMessage, e error, isFailure bool) {
 	d := p.retryDelayFunc(msg.Retried, e, NewTask(msg.Type, msg.Payload))
 	retryAt := time.Now().Add(d)
-	err := p.broker.Retry(msg, retryAt, e.Error())
+	err := p.broker.Retry(msg, retryAt, e.Error(), isFailure)
 	if err != nil {
 		errMsg := fmt.Sprintf("Could not move task id=%s from %q to %q", msg.ID, base.ActiveKey(msg.Queue), base.RetryKey(msg.Queue))
 		deadline, ok := ctx.Deadline()
@@ -288,7 +296,7 @@ func (p *processor) retry(ctx context.Context, msg *base.TaskMessage, e error) {
 		p.logger.Warnf("%s; Will retry syncing", errMsg)
 		p.syncRequestCh <- &syncRequest{
 			fn: func() error {
-				return p.broker.Retry(msg, retryAt, e.Error())
+				return p.broker.Retry(msg, retryAt, e.Error(), isFailure)
 			},
 			errMsg:   errMsg,
 			deadline: deadline,

processor_test.go

@@ -98,6 +98,7 @@ func TestProcessorSuccessWithSingleQueue(t *testing.T) {
 			logger:          testLogger,
 			broker:          rdbClient,
 			retryDelayFunc:  DefaultRetryDelayFunc,
+			isFailureFunc:   defaultIsFailureFunc,
 			syncCh:          syncCh,
 			cancelations:    base.NewCancelations(),
 			concurrency:     10,
@@ -190,6 +191,7 @@ func TestProcessorSuccessWithMultipleQueues(t *testing.T) {
 			logger:         testLogger,
 			broker:         rdbClient,
 			retryDelayFunc: DefaultRetryDelayFunc,
+			isFailureFunc:  defaultIsFailureFunc,
 			syncCh:         syncCh,
 			cancelations:   base.NewCancelations(),
 			concurrency:    10,
@@ -276,6 +278,7 @@ func TestProcessTasksWithLargeNumberInPayload(t *testing.T) {
 			logger:          testLogger,
 			broker:          rdbClient,
 			retryDelayFunc:  DefaultRetryDelayFunc,
+			isFailureFunc:   defaultIsFailureFunc,
 			syncCh:          syncCh,
 			cancelations:    base.NewCancelations(),
 			concurrency:     10,
@@ -395,6 +398,7 @@ func TestProcessorRetry(t *testing.T) {
 			logger:          testLogger,
 			broker:          rdbClient,
 			retryDelayFunc:  delayFunc,
+			isFailureFunc:   defaultIsFailureFunc,
 			syncCh:          nil,
 			cancelations:    base.NewCancelations(),
 			concurrency:     10,
@@ -486,6 +490,7 @@ func TestProcessorQueues(t *testing.T) {
 			logger:          testLogger,
 			broker:          nil,
 			retryDelayFunc:  DefaultRetryDelayFunc,
+			isFailureFunc:   defaultIsFailureFunc,
 			syncCh:          nil,
 			cancelations:    base.NewCancelations(),
 			concurrency:     10,
@@ -577,6 +582,7 @@ func TestProcessorWithStrictPriority(t *testing.T) {
 			logger:          testLogger,
 			broker:          rdbClient,
 			retryDelayFunc:  DefaultRetryDelayFunc,
+			isFailureFunc:   defaultIsFailureFunc,
 			syncCh:          syncCh,
 			cancelations:    base.NewCancelations(),
 			concurrency:     1, // Set concurrency to 1 to make sure tasks are processed one at a time.

recoverer.go

@@ -5,7 +5,7 @@
 package asynq
 
 import (
-	"fmt"
+	"context"
 	"sync"
 	"time"
 
@@ -17,6 +17,7 @@ type recoverer struct {
 	logger         *log.Logger
 	broker         base.Broker
 	retryDelayFunc RetryDelayFunc
+	isFailureFunc  func(error) bool
 
 	// channel to communicate back to the long running "recoverer" goroutine.
 	done chan struct{}
@@ -34,6 +35,7 @@ type recovererParams struct {
 	queues         []string
 	interval       time.Duration
 	retryDelayFunc RetryDelayFunc
+	isFailureFunc  func(error) bool
 }
 
 func newRecoverer(params recovererParams) *recoverer {
@@ -44,6 +46,7 @@ func newRecoverer(params recovererParams) *recoverer {
 		queues:         params.queues,
 		interval:       params.interval,
 		retryDelayFunc: params.retryDelayFunc,
+		isFailureFunc:  params.isFailureFunc,
 	}
 }
 
@@ -81,26 +84,25 @@ func (r *recoverer) recover() {
 		r.logger.Warn("recoverer: could not list deadline exceeded tasks")
 		return
 	}
-	const errMsg = "deadline exceeded"
 	for _, msg := range msgs {
 		if msg.Retried >= msg.Retry {
-			r.archive(msg, errMsg)
+			r.archive(msg, context.DeadlineExceeded)
 		} else {
-			r.retry(msg, errMsg)
+			r.retry(msg, context.DeadlineExceeded)
 		}
 	}
 }
 
-func (r *recoverer) retry(msg *base.TaskMessage, errMsg string) {
+func (r *recoverer) retry(msg *base.TaskMessage, err error) {
-	delay := r.retryDelayFunc(msg.Retried, fmt.Errorf(errMsg), NewTask(msg.Type, msg.Payload))
+	delay := r.retryDelayFunc(msg.Retried, err, NewTask(msg.Type, msg.Payload))
 	retryAt := time.Now().Add(delay)
-	if err := r.broker.Retry(msg, retryAt, errMsg); err != nil {
+	if err := r.broker.Retry(msg, retryAt, err.Error(), r.isFailureFunc(err)); err != nil {
 		r.logger.Warnf("recoverer: could not retry deadline exceeded task: %v", err)
 	}
 }
 
-func (r *recoverer) archive(msg *base.TaskMessage, errMsg string) {
+func (r *recoverer) archive(msg *base.TaskMessage, err error) {
-	if err := r.broker.Archive(msg, errMsg); err != nil {
+	if err := r.broker.Archive(msg, err.Error()); err != nil {
 		r.logger.Warnf("recoverer: could not move task to archive: %v", err)
 	}
 }

recoverer_test.go

@@ -234,6 +234,7 @@ func TestRecoverer(t *testing.T) {
 			queues:         []string{"default", "critical"},
 			interval:       1 * time.Second,
 			retryDelayFunc: func(n int, err error, task *Task) time.Duration { return 30 * time.Second },
+			isFailureFunc:  defaultIsFailureFunc,
 		})
 
 		var wg sync.WaitGroup
@@ -259,7 +260,7 @@ func TestRecoverer(t *testing.T) {
 			gotRetry := h.GetRetryMessages(t, r, qname)
 			var wantRetry []*base.TaskMessage // Note: construct message here since `LastFailedAt` is relative to each test run
 			for _, msg := range msgs {
-				wantRetry = append(wantRetry, h.TaskMessageAfterRetry(*msg, "deadline exceeded", runTime))
+				wantRetry = append(wantRetry, h.TaskMessageAfterRetry(*msg, "context deadline exceeded", runTime))
 			}
 			if diff := cmp.Diff(wantRetry, gotRetry, h.SortMsgOpt, cmpOpt); diff != "" {
 				t.Errorf("%s; mismatch found in %q: (-want, +got)\n%s", tc.desc, base.RetryKey(qname), diff)
@@ -269,7 +270,7 @@ func TestRecoverer(t *testing.T) {
 			gotArchived := h.GetArchivedMessages(t, r, qname)
 			var wantArchived []*base.TaskMessage
 			for _, msg := range msgs {
-				wantArchived = append(wantArchived, h.TaskMessageWithError(*msg, "deadline exceeded", runTime))
+				wantArchived = append(wantArchived, h.TaskMessageWithError(*msg, "context deadline exceeded", runTime))
 			}
 			if diff := cmp.Diff(wantArchived, gotArchived, h.SortMsgOpt, cmpOpt); diff != "" {
 				t.Errorf("%s; mismatch found in %q: (-want, +got)\n%s", tc.desc, base.ArchivedKey(qname), diff)

server.go

@@ -64,6 +64,14 @@ type Config struct {
 	// By default, it uses exponential backoff algorithm to calculate the delay.
 	RetryDelayFunc RetryDelayFunc
 
+	// Predicate function to determine whether the error returned from Handler is a failure.
+	// If the function returns false, Server will not increment the retried counter for the task,
+	// and Server won't record the queue stats (processed and failed stats) to avoid skewing the error
+	// rate of the queue.
+	//
+	// By default, if the given error is non-nil the function returns true.
+	IsFailure func(error) bool
+
 	// List of queues to process with given priority value. Keys are the names of the
 	// queues and values are associated priority value.
 	//
@@ -268,6 +276,8 @@ func DefaultRetryDelayFunc(n int, e error, t *Task) time.Duration {
 	return time.Duration(s) * time.Second
 }
 
+func defaultIsFailureFunc(err error) bool { return err != nil }
+
 var defaultQueueConfig = map[string]int{
 	base.DefaultQueueName: 1,
 }
@@ -293,6 +303,10 @@ func NewServer(r RedisConnOpt, cfg Config) *Server {
 	if delayFunc == nil {
 		delayFunc = DefaultRetryDelayFunc
 	}
+	isFailureFunc := cfg.IsFailure
+	if isFailureFunc == nil {
+		isFailureFunc = defaultIsFailureFunc
+	}
 	queues := make(map[string]int)
 	for qname, p := range cfg.Queues {
 		if err := base.ValidateQueueName(qname); err != nil {
@@ -362,6 +376,7 @@ func NewServer(r RedisConnOpt, cfg Config) *Server {
 		logger:          logger,
 		broker:          rdb,
 		retryDelayFunc:  delayFunc,
+		isFailureFunc:   isFailureFunc,
 		syncCh:          syncCh,
 		cancelations:    cancels,
 		concurrency:     n,
@@ -376,6 +391,7 @@ func NewServer(r RedisConnOpt, cfg Config) *Server {
 		logger:         logger,
 		broker:         rdb,
 		retryDelayFunc: delayFunc,
+		isFailureFunc:  isFailureFunc,
 		queues:         qnames,
 		interval:       1 * time.Minute,
 	})