# gpool - a generic context-aware resizable goroutines pool to bound concurrency.
[](https://github.com/avelino/awesome-go#goroutines)
<a>
<img src="https://img.shields.io/github/v/tag/sherifabdlnaby/gpool?label=release&sort=semver">
</a>
[](http://godoc.org/github.com/sherifabdlnaby/gpool)
[](https://goreportcard.com/report/github.com/sherifabdlnaby/gpool)
[](https://travis-ci.org/sherifabdlnaby/gpool)
[](https://codecov.io/gh/sherifabdlnaby/gpool)
[](https://github.com/SherifAbdlNaby/gpool/blob/master/LICENSE)
## Installation
``` bash
$ go get github.com/sherifabdlnaby/gpool
```
``` go
import "github.com/sherifabdlnaby/gpool"
```
## Introduction
Easily manages a resizeable pool of context aware goroutines to bound concurrency, A **`Job`** is **Enqueued** to the pool and only **`N`** jobs can be processing concurrently at the same time.
- A Job is simply a `func(){}`, when you `Enqueue(..)` a job, the enqueue call will return *ONCE* the job has **started** processing. Otherwise if the pool is full it will **block** until:
1. pool has room for the job.
2. job's `context` is canceled.
3. the pool is stopped.
- The Pool can be re-sized using `Resize()` that will resize the pool in a concurrent safe-way. `Resize` can enlarge the pool and any blocked enqueue will unblock after pool is resized, in case of shrinking the pool `resize` will not affect any already processing/waiting jobs.
- Enqueuing a Job will return error `nil` once a job starts, `ErrPoolClosed` if the pool is closed, or **the context's error if the job's context is canceled while blocking waiting for the pool.**
- Stopping the Pool using `pool.Stop()` will **wait** for all processing jobs to finish before returning, it will also unblock any **blocked** job enqueues (enqueues will return ErrPoolClosed).
- `Start`, `Stop`, and `Resize(N)` are all concurrent safe and can be called from multiple goroutines, subsequent calls of Start or Stop has no effect unless called interchangeably.
further documentation at : [](http://godoc.org/github.com/sherifabdlnaby/gpool)
------------------------------------------------------
## Usage
- Create new pool
```
pool, err := gpool.NewPool(concurrency)
```
- Enqueue a job
```
job := func() {
time.Sleep(2000 * time.Millisecond)
fmt.Println("did some work")
}
// Enqueue Job
err := pool.Enqueue(ctx, job)
```
A call to `pool.Enqueue()` will return `nil` if `job` started processing, blocks if the pool is full, `ctx.Err()` if context was canceled while waiting/blocking, or finally `ErrPoolClosed` if the pool stopped or was never started.
- Resize the pool
```
err = pool.Resize(size)
```
Will live change the size of the pool, If new size is larger, waiting job enqueues from another goroutines will be unblocked to fit the new size, and if new size is smaller, any new enqueues will block until the current size of the pool is less than the new one.
- Stop the pool
```
pool.Stop()
```
- ALL Blocked/Waiting jobs will return immediately.
- Stop() WILL Block until all running jobs is done.
- Different types of "Enqueues"
- `Enqueue(ctx, job)` returns ONCE the job has started executing (not after job finishes/return)
- `EnqueueAndWait(ctx, job)` returns ONCE the job has started **and** finished executing.
- `TryEnqueue(job)` will not block if the pool is full, returns `true` ONCE the job has started executing and `false` if pool is full.
- `TryEnqueueAndWait(job)` will not block if the pool is full, returns `true` ONCE the job has started **and** finished executing. and `false` if pool is full.
------------------------------------------------------
## Benchmarks
``` bash
$ go test -bench=. -cpu=2 -benchmem
```
```
go test -bench=. -cpu=2 -benchmem
goos: darwin
goarch: amd64
pkg: github.com/sherifabdlnaby/gpool
BenchmarkThroughput/PoolSize[2]-2 853724 730 ns/op 125 B/op 2 allocs/op
BenchmarkThroughput/PoolSize[10]-2 3647638 329 ns/op 10 B/op 0 allocs/op
BenchmarkThroughput/PoolSize[100]-2 4869789 248 ns/op 0 B/op 0 allocs/op
BenchmarkThroughput/PoolSize[1000]-2 4320566 280 ns/op 0 B/op 0 allocs/op
BenchmarkBulkJobs_UnderLimit/PoolSize[2]BulkJobs[2]-2 530328 2146 ns/op 275 B/op 5 allocs/op
BenchmarkBulkJobs_UnderLimit/PoolSize[2]BulkJobs[100]-2 10000 112478 ns/op 12737 B/op 239 allocs/op
BenchmarkBulkJobs_UnderLimit/PoolSize[2]BulkJobs[1000]-2 1069 1109384 ns/op 126943 B/op 2380 allocs/op
BenchmarkBulkJobs_UnderLimit/PoolSize[10]BulkJobs[2]-2 1417808 844 ns/op 58 B/op 1 allocs/op
BenchmarkBulkJobs_UnderLimit/PoolSize[10]BulkJobs[100]-2 30556 39187 ns/op 1764 B/op 33 allocs/op
BenchmarkBulkJobs_UnderLimit/PoolSize[10]BulkJobs[1000]-2 3012 385652 ns/op 15737 B/op 295 allocs/op
BenchmarkBulkJobs_UnderLimit/PoolSize[100]BulkJobs[2]-2 1986571 609 ns/op 16 B/op 1 allocs/op
BenchmarkBulkJobs_UnderLimit/PoolSize[100]BulkJobs[100]-2 41235 29004 ns/op 37 B/op 1 allocs/op
BenchmarkBulkJobs_UnderLimit/PoolSize[100]BulkJobs[1000]-2 4080 290791 ns/op 188 B/op 4 allocs/op
BenchmarkBulkJobs_UnderLimit/PoolSize[1000]BulkJobs[2]-2 1963564 605 ns/op 16 B/op 1 allocs/op
BenchmarkBulkJobs_UnderLimit/PoolSize[1000]BulkJobs[100]-2 42000 28442 ns/op 16 B/op 1 allocs/op
BenchmarkBulkJobs_UnderLimit/PoolSize[1000]BulkJobs[1000]-2 4333 284865 ns/op 17 B/op 1 allocs/op
BenchmarkBulkJobs_UnderLimit/PoolSize[10000]BulkJobs[2]-2 1963168 611 ns/op 16 B/op 1 allocs/op
BenchmarkBulkJobs_UnderLimit/PoolSize[10000]BulkJobs[100]-2 42238 28419 ns/op 16 B/op 1 allocs/op
BenchmarkBulkJobs_UnderLimit/PoolSize[10000]BulkJobs[1000]-2 4171 283981 ns/op 29 B/op 1 allocs/op
```
**BenchmarkOneThroughput/PoolSize[S]** = Enqueue Async Jobs ( Will not wait for result ) in a Pool of size = `S`
**BenchmarkBulkJobs/PoolSize[S]BulkJobs[J]** = Enqueue `J` Jobs In Pool of size `S` at a time where `J` < `S`
------------------------------------------------------
## Examples
### Example 1 - Simple Job Enqueue
```go
func main() {
concurrency := 2
// Create and start pool.
pool, _ := gpool.NewPool(concurrency)
defer pool.Stop()
// Create JOB
resultChan1 := make(chan int)
ctx := context.Background()
job := func() {
time.Sleep(2000 * time.Millisecond)
resultChan1 <- 1337
}
// Enqueue Job
err1 := pool.Enqueue(ctx, job)
if err1 != nil {
log.Printf("Job was not enqueued. Error: [%s]", err1.Error())
return
}
log.Printf("Job Enqueued and started processing")
log.Printf("Job Done, Received: %v", <-resultChan1)
}
```
----------
### Example 2 - Enqueue A Job with Timeout
```go
func main() {
concurrency := 2
// Create and start pool.
pool, _ := gpool.NewPool(concurrency)
defer pool.Stop()
// Create JOB
resultChan := make(chan int)
ctx := context.Background()
job := func() {
resultChan <- 1337
}
// Enqueue 2 Jobs to fill pool (Will not finish unless we pull result from resultChan)
_ = pool.Enqueue(ctx, job)
_ = pool.Enqueue(ctx, job)
ctxWithTimeout, _ := context.WithTimeout(ctx, 1000 * time.Millisecond)
// Will block for 1 second only because of Timeout
err1 := pool.Enqueue(ctxWithTimeout, job)
if err1 != nil {
log.Printf("Job was not enqueued. Error: [%s]", err1.Error())
}
log.Printf("Job 1 Done, Received: %v", <-resultChan)
log.Printf("Job 2 Done, Received: %v", <-resultChan)
}
```
----------
### Example 3
``` go
// size Workers / Concurrent jobs of the Pool
const concurrency = 2
func main() {
pool, _ := gpool.NewPool(concurrency)
defer pool.Stop()
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
go func() {
for i := 0; i < 10; i++ {
// Small Interval for more readable output
time.Sleep(500 * time.Millisecond)
go func(i int) {
x := make(chan int, 1)
log.Printf("Job [%v] Enqueueing", i)
err := pool.Enqueue(ctx, func() {
time.Sleep(2000 * time.Millisecond)
x <- i
})
if err != nil {
log.Printf("Job [%v] was not enqueued. [%s]", i, err.Error())
return
}
log.Printf("Job [%v] Enqueue-ed ", i)
log.Printf("Job [%v] Receieved, Result: [%v]", i, <-x)
}(i)
}
}()
// Uncomment to demonstrate ctx cancel of jobs.
//time.Sleep(100 * time.Millisecond)
//cancel()
time.Sleep(5000 * time.Millisecond)
fmt.Println("Stopping...")
pool.Stop()
fmt.Println("Stopped")
fmt.Println("Sleeping for couple of seconds so canceled job have a chance to print out their status")
time.Sleep(4000 * time.Millisecond)
}
```
#### Output
```
2019/01/08 20:15:39 Job [0] Enqueueing
2019/01/08 20:15:39 Job [0] Enqueue-ed
2019/01/08 20:15:39 Job [1] Enqueueing
2019/01/08 20:15:39 Job [1] Enqueue-ed
2019/01/08 20:15:40 Job [2] Enqueueing
2019/01/08 20:15:40 Job [3] Enqueueing
2019/01/08 20:15:41 Job [0] Receieved, Result: [0]
2019/01/08 20:15:41 Job [2] Enqueue-ed
2019/01/08 20:15:41 Job [4] Enqueueing
2019/01/08 20:15:41 Job [3] Enqueue-ed
2019/01/08 20:15:41 Job [1] Receieved, Result: [1]
2019/01/08 20:15:41 Job [5] Enqueueing
2019/01/08 20:15:42 Job [6] Enqueueing
2019/01/08 20:15:42 Job [7] Enqueueing
2019/01/08 20:15:43 Job [4] Enqueue-ed
2019/01/08 20:15:43 Job [2] Receieved, Result: [2]
2019/01/08 20:15:43 Job [8] Enqueueing
Stopping...
2019/01/08 20:15:43 Job [7] was not enqueued. [pool is closed]
2019/01/08 20:15:43 Job [5] was not enqueued. [pool is closed]
2019/01/08 20:15:43 Job [6] was not enqueued. [pool is closed]
2019/01/08 20:15:43 Job [3] Receieved, Result: [3]
2019/01/08 20:15:43 Job [8] was not enqueued. [pool is closed]
2019/01/08 20:15:43 Job [9] Enqueueing
Stopped
2019/01/08 20:15:45 Job [4] Receieved, Result: [4]
Sleeping for couple of seconds so canceled job have a chance to print out their status
2019/01/08 20:15:45 Job [9] was not enqueued. [pool is closed]
Process finished with exit code 0
```
# License
[MIT License](https://raw.githubusercontent.com/sherifabdlnaby/gpool/blob/master/LICENSE)
Copyright (c) 2019 Sherif Abdel-Naby
# Contribution
PR(s) are Open and Welcomed.