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// Copyright 2020 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.
package queue
import (
// ChannelUniqueQueueType is the type for channel queue
const ChannelUniqueQueueType Type = "unique-channel"
// ChannelUniqueQueueConfiguration is the configuration for a ChannelUniqueQueue
type ChannelUniqueQueueConfiguration ChannelQueueConfiguration
// ChannelUniqueQueue implements UniqueQueue
// It is basically a thin wrapper around a WorkerPool but keeps a store of
// what has been pushed within a table.
// Please note that this Queue does not guarantee that a particular
// task cannot be processed twice or more at the same time. Uniqueness is
// only guaranteed whilst the task is waiting in the queue.
type ChannelUniqueQueue struct {
lock sync.Mutex
table map[Data]bool
exemplar interface{}
workers int
name string
// NewChannelUniqueQueue create a memory channel queue
func NewChannelUniqueQueue(handle HandlerFunc, cfg, exemplar interface{}) (Queue, error) {
configInterface, err := toConfig(ChannelUniqueQueueConfiguration{}, cfg)
if err != nil {
return nil, err
config := configInterface.(ChannelUniqueQueueConfiguration)
if config.BatchLength == 0 {
config.BatchLength = 1
queue := &ChannelUniqueQueue{
table: map[Data]bool{},
exemplar: exemplar,
workers: config.Workers,
name: config.Name,
queue.WorkerPool = NewWorkerPool(func(data ...Data) {
for _, datum := range data {
delete(queue.table, datum)
}, config.WorkerPoolConfiguration)
queue.qid = GetManager().Add(queue, ChannelUniqueQueueType, config, exemplar)
return queue, nil
// Run starts to run the queue
func (q *ChannelUniqueQueue) Run(atShutdown, atTerminate func(context.Context, func())) {
atShutdown(context.Background(), func() {
log.Warn("ChannelUniqueQueue: %s is not shutdownable!",
atTerminate(context.Background(), func() {
log.Warn("ChannelUniqueQueue: %s is not terminatable!",
log.Debug("ChannelUniqueQueue: %s Starting",
go func() {
_ = q.AddWorkers(q.workers, 0)
// Push will push data into the queue if the data is not already in the queue
func (q *ChannelUniqueQueue) Push(data Data) error {
return q.PushFunc(data, nil)
// PushFunc will push data into the queue
func (q *ChannelUniqueQueue) PushFunc(data Data, fn func() error) error {
if !assignableTo(data, q.exemplar) {
return fmt.Errorf("Unable to assign data: %v to same type as exemplar: %v in queue: %s", data, q.exemplar,
locked := true
defer func() {
if locked {
if _, ok := q.table[data]; ok {
return ErrAlreadyInQueue
// FIXME: We probably need to implement some sort of limit here
// If the downstream queue blocks this table will grow without limit
q.table[data] = true
if fn != nil {
err := fn()
if err != nil {
delete(q.table, data)
return err
locked = false
return nil
// Has checks if the data is in the queue
func (q *ChannelUniqueQueue) Has(data Data) (bool, error) {
defer q.lock.Unlock()
_, has := q.table[data]
return has, nil
// Name returns the name of this queue
func (q *ChannelUniqueQueue) Name() string {
func init() {
queuesMap[ChannelUniqueQueueType] = NewChannelUniqueQueue