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pool.go
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pool.go
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// MIT License
// Copyright (c) 2018 Andy Pan
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
package ants
import (
"sync"
"sync/atomic"
"time"
"github.com/panjf2000/ants/v2/internal"
)
// Pool accepts the tasks from client, it limits the total of goroutines to a given number by recycling goroutines.
type Pool struct {
// capacity of the pool, a negative value means that the capacity of pool is limitless, an infinite pool is used to
// avoid potential issue of endless blocking caused by nested usage of a pool: submitting a task to pool
// which submits a new task to the same pool.
capacity int32
// running is the number of the currently running goroutines.
running int32
// lock for protecting the worker queue.
lock sync.Locker
// workers is a slice that store the available workers.
workers workerArray
// state is used to notice the pool to closed itself.
state int32
// cond for waiting to get an idle worker.
cond *sync.Cond
// workerCache speeds up the obtainment of a usable worker in function:retrieveWorker.
workerCache sync.Pool
// blockingNum is the number of the goroutines already been blocked on pool.Submit, protected by pool.lock
blockingNum int
options *Options
}
// purgePeriodically clears expired workers periodically which runs in an individual goroutine, as a scavenger.
func (p *Pool) purgePeriodically() {
heartbeat := time.NewTicker(p.options.ExpiryDuration)
defer heartbeat.Stop()
for range heartbeat.C {
if p.IsClosed() {
break
}
p.lock.Lock()
expiredWorkers := p.workers.retrieveExpiry(p.options.ExpiryDuration)
p.lock.Unlock()
// Notify obsolete workers to stop.
// This notification must be outside the p.lock, since w.task
// may be blocking and may consume a lot of time if many workers
// are located on non-local CPUs.
for i := range expiredWorkers {
expiredWorkers[i].task <- nil
expiredWorkers[i] = nil
}
// There might be a situation that all workers have been cleaned up(no any worker is running)
// while some invokers still get stuck in "p.cond.Wait()",
// then it ought to wake all those invokers.
if p.Running() == 0 {
p.cond.Broadcast()
}
}
}
// NewPool generates an instance of ants pool.
func NewPool(size int, options ...Option) (*Pool, error) {
opts := loadOptions(options...)
if size <= 0 {
size = -1
}
if expiry := opts.ExpiryDuration; expiry < 0 {
return nil, ErrInvalidPoolExpiry
} else if expiry == 0 {
opts.ExpiryDuration = DefaultCleanIntervalTime
}
if opts.Logger == nil {
opts.Logger = defaultLogger
}
p := &Pool{
capacity: int32(size),
lock: internal.NewSpinLock(),
options: opts,
}
p.workerCache.New = func() interface{} {
return &goWorker{
pool: p,
task: make(chan func(), workerChanCap),
}
}
if p.options.PreAlloc {
if size == -1 {
return nil, ErrInvalidPreAllocSize
}
p.workers = newWorkerArray(loopQueueType, size)
} else {
p.workers = newWorkerArray(stackType, 0)
}
p.cond = sync.NewCond(p.lock)
// Start a goroutine to clean up expired workers periodically.
go p.purgePeriodically()
return p, nil
}
// ---------------------------------------------------------------------------
// Submit submits a task to this pool.
//
// Note that you are allowed to call Pool.Submit() from the current Pool.Submit(),
// but what calls for special attention is that you will get blocked with the latest
// Pool.Submit() call once the current Pool runs out of its capacity, and to avoid this,
// you should instantiate a Pool with ants.WithNonblocking(true).
func (p *Pool) Submit(task func()) error {
if p.IsClosed() {
return ErrPoolClosed
}
var w *goWorker
if w = p.retrieveWorker(); w == nil {
return ErrPoolOverload
}
w.task <- task
return nil
}
// Running returns the amount of the currently running goroutines.
func (p *Pool) Running() int {
return int(atomic.LoadInt32(&p.running))
}
// Free returns the amount of available goroutines to work, -1 indicates this pool is unlimited.
func (p *Pool) Free() int {
c := p.Cap()
if c < 0 {
return -1
}
return c - p.Running()
}
// Cap returns the capacity of this pool.
func (p *Pool) Cap() int {
return int(atomic.LoadInt32(&p.capacity))
}
// Tune changes the capacity of this pool, note that it is noneffective to the infinite or pre-allocation pool.
func (p *Pool) Tune(size int) {
capacity := p.Cap()
if capacity == -1 || size <= 0 || size == capacity || p.options.PreAlloc {
return
}
atomic.StoreInt32(&p.capacity, int32(size))
if size > capacity {
if size-capacity == 1 {
p.cond.Signal()
return
}
p.cond.Broadcast()
}
}
// IsClosed indicates whether the pool is closed.
func (p *Pool) IsClosed() bool {
return atomic.LoadInt32(&p.state) == CLOSED
}
// Release closes this pool and releases the worker queue.
func (p *Pool) Release() {
atomic.StoreInt32(&p.state, CLOSED)
p.lock.Lock()
p.workers.reset()
p.lock.Unlock()
// There might be some callers waiting in retrieveWorker(), so we need to wake them up to prevent
// those callers blocking infinitely.
p.cond.Broadcast()
}
// Reboot reboots a closed pool.
func (p *Pool) Reboot() {
if atomic.CompareAndSwapInt32(&p.state, CLOSED, OPENED) {
go p.purgePeriodically()
}
}
// ---------------------------------------------------------------------------
// incRunning increases the number of the currently running goroutines.
func (p *Pool) incRunning() {
atomic.AddInt32(&p.running, 1)
}
// decRunning decreases the number of the currently running goroutines.
func (p *Pool) decRunning() {
atomic.AddInt32(&p.running, -1)
}
// retrieveWorker returns an available worker to run the tasks.
func (p *Pool) retrieveWorker() (w *goWorker) {
spawnWorker := func() {
w = p.workerCache.Get().(*goWorker)
w.run()
}
p.lock.Lock()
w = p.workers.detach()
if w != nil { // first try to fetch the worker from the queue
p.lock.Unlock()
} else if capacity := p.Cap(); capacity == -1 || capacity > p.Running() {
// if the worker queue is empty and we don't run out of the pool capacity,
// then just spawn a new worker goroutine.
p.lock.Unlock()
spawnWorker()
} else { // otherwise, we'll have to keep them blocked and wait for at least one worker to be put back into pool.
if p.options.Nonblocking {
p.lock.Unlock()
return
}
retry:
if p.options.MaxBlockingTasks != 0 && p.blockingNum >= p.options.MaxBlockingTasks {
p.lock.Unlock()
return
}
p.blockingNum++
p.cond.Wait() // block and wait for an available worker
p.blockingNum--
var nw int
if nw = p.Running(); nw == 0 { // awakened by the scavenger
p.lock.Unlock()
if !p.IsClosed() {
spawnWorker()
}
return
}
if w = p.workers.detach(); w == nil {
if nw < capacity {
p.lock.Unlock()
spawnWorker()
return
}
goto retry
}
p.lock.Unlock()
}
return
}
// revertWorker puts a worker back into free pool, recycling the goroutines.
func (p *Pool) revertWorker(worker *goWorker) bool {
if capacity := p.Cap(); (capacity > 0 && p.Running() > capacity) || p.IsClosed() {
p.cond.Broadcast()
return false
}
worker.recycleTime = time.Now()
p.lock.Lock()
// To avoid memory leaks, add a double check in the lock scope.
// Issue: https://github.com/panjf2000/ants/issues/113
if p.IsClosed() {
p.lock.Unlock()
return false
}
err := p.workers.insert(worker)
if err != nil {
p.lock.Unlock()
return false
}
// Notify the invoker stuck in 'retrieveWorker()' of there is an available worker in the worker queue.
p.cond.Signal()
p.lock.Unlock()
return true
}