A goroutine pool for Go
[![Build Status][1]][2] [![codecov][3]][4] [![goreportcard for panjf2000/ants][5]][6] [![godoc for panjf2000/ants][7]][8] [![MIT Licence][9]][10] [中文](README_ZH.md) | [Project Tutorial](http://blog.taohuawu.club/article/goroutine-pool) 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: - Automatically managing and recycling a massive number of goroutines. - Periodically purging overdue goroutines. - Friendly interfaces: submitting tasks, getting the number of running goroutines, tuning capacity of pool dynamically, closing pool. - Handle panic gracefully to prevent programs from crash. - Efficient in memory usage and it even achieves higher performance than unlimited goroutines in golang. ## Tested in the following Golang versions: - 1.8.x - 1.9.x - 1.10.x - 1.11.x - 1.12.x ## How to install ``` sh go get -u github.com/panjf2000/ants ``` Or, using glide: ``` sh glide get github.com/panjf2000/ants ``` ## How to use Just take a imagination that your program starts a massive number of goroutines, from which a vast amount of memory will be consumed. 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: ``` go package main import ( "fmt" "sync" "sync/atomic" "time" "github.com/panjf2000/ants" ) 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) } ``` ## Integrate with http server ```go package main import ( "io/ioutil" "net/http" "github.com/panjf2000/ants" ) type Request struct { Param []byte Result chan []byte } func main() { pool, _ := ants.NewPoolWithFunc(100, func(payload interface{}) { request, ok := payload.(*Request) if !ok { return } reverseParam := func(s []byte) []byte { for i, j := 0, len(s)-1; i < j; i, j = i+1, j-1 { s[i], s[j] = s[j], s[i] } return s }(request.Param) request.Result <- reverseParam }) defer pool.Release() http.HandleFunc("/reverse", func(w http.ResponseWriter, r *http.Request) { param, err := ioutil.ReadAll(r.Body) if err != nil { http.Error(w, "request error", http.StatusInternalServerError) } defer r.Body.Close() request := &Request{Param: param, Result: make(chan []byte)} // Throttle the requests traffic with ants pool. This process is asynchronous and // you can receive a result from the channel defined outside. if err := pool.Invoke(request); err != nil { http.Error(w, "throttle limit error", http.StatusInternalServerError) } w.Write(<-request.Result) }) http.ListenAndServe(":8080", nil) } ``` ## Submit tasks Tasks can be submitted by calling `ants.Submit(func())` ```go ants.Submit(func(){}) ``` ## Customize limited pool `ants` also supports customizing the capacity of pool. You can invoke the `NewPool` function to instantiate a pool with a given capacity, as following: ``` go // Set 10000 the size of goroutine pool p, _ := ants.NewPool(10000) // Submit a task p.Submit(func(){}) ``` ## Tune pool capacity in runtime You can tune the capacity of `ants` pool in runtime with `Tune(int)`: ``` go pool.Tune(1000) // Tune its capacity to 1000 pool.Tune(100000) // Tune its capacity to 100000 ``` Don't worry about the synchronous problems in this case, the function here is thread-safe (or should be called goroutine-safe). ## Release Pool ```go pool.Release() ``` ## 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. ## Benchmarks ``` OS: macOS High Sierra Processor: 2.7 GHz Intel Core i5 Memory: 8 GB 1867 MHz DDR3 Go Version: 1.9 ```