A goroutine pool for Go

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📖 Introduction

Library ants implements a goroutine pool with fixed capacity, managing and recycling a massive number of goroutines, allowing developers to limit the number of goroutines in your concurrent programs.

🚀 Features:

• Managing and recycling a massive number of goroutines automatically
• Purging overdue goroutines periodically
• Abundant APIs: submitting tasks, getting the number of running goroutines, tuning the capacity of the pool dynamically, releasing the pool, rebooting the pool
• Handle panic gracefully to prevent programs from crash
• Efficient in memory usage and it even achieves higher performance than unlimited goroutines in Golang
• Nonblocking mechanism

💡 How ants works

Flow Diagram

Activity Diagrams

🧰 How to install

For ants v1

go get -u github.com/panjf2000/ants

For ants v2 (with GO111MODULE=on)

go get -u github.com/panjf2000/ants/v2

🛠 How to use

Just imagine that your program starts a massive number of goroutines, resulting in a huge consumption of memory. To mitigate that kind of situation, all you need to do is to import ants package and submit all your tasks to a default pool with fixed capacity, activated when package ants is imported:

package main

import (
	"fmt"
	"sync"
	"sync/atomic"
	"time"

	"github.com/panjf2000/ants/v2"
)

var sum int32

func myFunc(i interface{}) {
	n := i.(int32)
	atomic.AddInt32(&sum, n)
	fmt.Printf("run with %d\n", n)
}

func demoFunc() {
	time.Sleep(10 * time.Millisecond)
	fmt.Println("Hello World!")
}

func main() {
	defer ants.Release()

	runTimes := 1000

	// Use the common pool.
	var wg sync.WaitGroup
	syncCalculateSum := func() {
		demoFunc()
		wg.Done()
	}
	for i := 0; i < runTimes; i++ {
		wg.Add(1)
		_ = ants.Submit(syncCalculateSum)
	}
	wg.Wait()
	fmt.Printf("running goroutines: %d\n", ants.Running())
	fmt.Printf("finish all tasks.\n")

	// Use the pool with a function,
	// set 10 to the capacity of goroutine pool and 1 second for expired duration.
	p, _ := ants.NewPoolWithFunc(10, func(i interface{}) {
		myFunc(i)
		wg.Done()
	})
	defer p.Release()
	// Submit tasks one by one.
	for i := 0; i < runTimes; i++ {
		wg.Add(1)
		_ = p.Invoke(int32(i))
	}
	wg.Wait()
	fmt.Printf("running goroutines: %d\n", p.Running())
	fmt.Printf("finish all tasks, result is %d\n", sum)
	if sum != 499500 {
		panic("the final result is wrong!!!")
	}

	// Use the MultiPool and set the capacity of the 10 goroutine pools to unlimited.
	// If you use -1 as the pool size parameter, the size will be unlimited.
	// There are two load-balancing algorithms for pools: ants.RoundRobin and ants.LeastTasks.
	mp, _ := ants.NewMultiPool(10, -1, ants.RoundRobin)
	defer mp.ReleaseTimeout(5 * time.Second)
	for i := 0; i < runTimes; i++ {
		wg.Add(1)
		_ = mp.Submit(syncCalculateSum)
	}
	wg.Wait()
	fmt.Printf("running goroutines: %d\n", mp.Running())
	fmt.Printf("finish all tasks.\n")

	// Use the MultiPoolFunc and set the capacity of 10 goroutine pools to (runTimes/10).
	mpf, _ := ants.NewMultiPoolWithFunc(10, runTimes/10, func(i interface{}) {
		myFunc(i)
		wg.Done()
	}, ants.LeastTasks)
	defer mpf.ReleaseTimeout(5 * time.Second)
	for i := 0; i < runTimes; i++ {
		wg.Add(1)
		_ = mpf.Invoke(int32(i))
	}
	wg.Wait()
	fmt.Printf("running goroutines: %d\n", mpf.Running())
	fmt.Printf("finish all tasks, result is %d\n", sum)
	if sum != 499500*2 {
		panic("the final result is wrong!!!")
	}
}

Functional options for ants pool

// Option represents the optional function.
type Option func(opts *Options)

// Options contains all options which will be applied when instantiating a ants pool.
type Options struct {
	// ExpiryDuration is a period for the scavenger goroutine to clean up those expired workers,
	// the scavenger scans all workers every `ExpiryDuration` and clean up those workers that haven't been
	// used for more than `ExpiryDuration`.
	ExpiryDuration time.Duration

	// PreAlloc indicates whether to make memory pre-allocation when initializing Pool.
	PreAlloc bool

	// Max number of goroutine blocking on pool.Submit.
	// 0 (default value) means no such limit.
	MaxBlockingTasks int

	// When Nonblocking is true, Pool.Submit will never be blocked.
	// ErrPoolOverload will be returned when Pool.Submit cannot be done at once.
	// When Nonblocking is true, MaxBlockingTasks is inoperative.
	Nonblocking bool

	// PanicHandler is used to handle panics from each worker goroutine.
	// if nil, panics will be thrown out again from worker goroutines.
	PanicHandler func(interface{})

	// Logger is the customized logger for logging info, if it is not set,
	// default standard logger from log package is used.
	Logger Logger
}

// WithOptions accepts the whole options config.
func WithOptions(options Options) Option {
	return func(opts *Options) {
		*opts = options
	}
}

// WithExpiryDuration sets up the interval time of cleaning up goroutines.
func WithExpiryDuration(expiryDuration time.Duration) Option {
	return func(opts *Options) {
		opts.ExpiryDuration = expiryDuration
	}
}

// WithPreAlloc indicates whether it should malloc for workers.
func WithPreAlloc(preAlloc bool) Option {
	return func(opts *Options) {
		opts.PreAlloc = preAlloc
	}
}

// WithMaxBlockingTasks sets up the maximum number of goroutines that are blocked when it reaches the capacity of pool.
func WithMaxBlockingTasks(maxBlockingTasks int) Option {
	return func(opts *Options) {
		opts.MaxBlockingTasks = maxBlockingTasks
	}
}

// WithNonblocking indicates that pool will return nil when there is no available workers.
func WithNonblocking(nonblocking bool) Option {
	return func(opts *Options) {
		opts.Nonblocking = nonblocking
	}
}

// WithPanicHandler sets up panic handler.
func WithPanicHandler(panicHandler func(interface{})) Option {
	return func(opts *Options) {
		opts.PanicHandler = panicHandler
	}
}

// WithLogger sets up a customized logger.
func WithLogger(logger Logger) Option {
	return func(opts *Options) {
		opts.Logger = logger
	}
}

ants.Optionscontains all optional configurations of the ants pool, which allows you to customize the goroutine pool by invoking option functions to set up each configuration in NewPool/NewPoolWithFuncmethod.

Customize limited pool

ants also supports customizing the capacity of the pool. You can invoke the NewPool method to instantiate a pool with a given capacity, as follows:

p, _ := ants.NewPool(10000)

Submit tasks

Tasks can be submitted by calling ants.Submit(func())

ants.Submit(func(){})

Tune pool capacity in runtime

You can tune the capacity of ants pool in runtime with Tune(int):

pool.Tune(1000) // Tune its capacity to 1000
pool.Tune(100000) // Tune its capacity to 100000

Don't worry about the contention problems in this case, the method here is thread-safe (or should be called goroutine-safe).

Pre-malloc goroutine queue in pool

ants allows you to pre-allocate the memory of the goroutine queue in the pool, which may get a performance enhancement under some special certain circumstances such as the scenario that requires a pool with ultra-large capacity, meanwhile, each task in goroutine lasts for a long time, in this case, pre-mallocing will reduce a lot of memory allocation in goroutine queue.

// ants will pre-malloc the whole capacity of pool when you invoke this method
p, _ := ants.NewPool(100000, ants.WithPreAlloc(true))

Release Pool

pool.Release()

Reboot Pool

// A pool that has been released can be still used once you invoke the Reboot().
pool.Reboot()

⚙️ About sequence

All tasks submitted to ants pool will not be guaranteed to be addressed in order, because those tasks scatter among a series of concurrent workers, thus those tasks would be executed concurrently.

👏 Contributors

Please read our Contributing Guidelines before opening a PR and thank you to all the developers who already made contributions to ants!

📄 License

The source code in ants is available under the MIT License.

📚 Relevant Articles

• Goroutine 并发调度模型深度解析之手撸一个高性能 goroutine 池
• Visually Understanding Worker Pool
• The Case For A Go Worker Pool
• Go Concurrency - GoRoutines, Worker Pools and Throttling Made Simple

🖥 Use cases

business companies

The following companies/organizations use ants in production.

open-source software

The open-source projects below do concurrent programming with the help of ants.

• gnet: A high-performance, lightweight, non-blocking, event-driven networking framework written in pure Go.
• milvus: An open-source vector database for scalable similarity search and AI applications.
• nps: A lightweight, high-performance, powerful intranet penetration proxy server, with a powerful web management terminal.
• siyuan: SiYuan is a local-first personal knowledge management system that supports complete offline use, as well as end-to-end encrypted synchronization.
• osmedeus: A Workflow Engine for Offensive Security.
• jitsu: An open-source Segment alternative. Fully-scriptable data ingestion engine for modern data teams. Set-up a real-time data pipeline in minutes, not days.
• triangula: Generate high-quality triangulated and polygonal art from images.
• teler: Real-time HTTP Intrusion Detection.
• bsc: A Binance Smart Chain client based on the go-ethereum fork.
• jaeles: The Swiss Army knife for automated Web Application Testing.
• devlake: The open-source dev data platform & dashboard for your DevOps tools.
• matrixone: MatrixOne is a future-oriented hyper-converged cloud and edge native DBMS that supports transactional, analytical, and streaming workloads with a simplified and distributed database engine, across multiple data centers, clouds, edges and other heterogeneous infrastructures.
• bk-bcs: BlueKing Container Service (BCS, same below) is a container management and orchestration platform for the micro-services under the BlueKing ecosystem.
• trueblocks-core: TrueBlocks improves access to blockchain data for any EVM-compatible chain (particularly Ethereum mainnet) while remaining entirely local.
• openGemini: openGemini is an open-source,cloud-native time-series database(TSDB) that can be widely used in IoT, Internet of Vehicles(IoV), O&M monitoring, and industrial Internet scenarios.
• AdGuardDNS: AdGuard DNS is an alternative solution for tracker blocking, privacy protection, and parental control.
• WatchAD2.0: WatchAD2.0 是 360 信息安全中心开发的一款针对域安全的日志分析与监控系统，它可以收集所有域控上的事件日志、网络流量，通过特征匹配、协议分析、历史行为、敏感操作和蜜罐账户等方式来检测各种已知与未知威胁，功能覆盖了大部分目前的常见内网域渗透手法。
• vanus: Vanus is a Serverless, event streaming system with processing capabilities. It easily connects SaaS, Cloud Services, and Databases to help users build next-gen Event-driven Applications.
• trpc-go: A pluggable, high-performance RPC framework written in Golang.
• motan-go: a remote procedure call (RPC) framework for the rapid development of high-performance distributed services.

All use cases:

• Repositories that depend on ants/v2

• Repositories that depend on ants/v1

If you have ants integrated into projects, feel free to open a pull request refreshing this list of use cases.

🔋 JetBrains OS licenses

ants had been being developed with GoLand under the free JetBrains Open Source license(s) granted by JetBrains s.r.o., hence I would like to express my thanks here.

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