semaphore go

Fast resizable golang semaphore primitive

Programming language: Go

License: MIT License

Tags: Workers     Goroutines     Task Queue     Semaphore    

Latest version: v2.4.1

README

semaphore

[](LICENSE)

Fast resizable golang semaphore based on CAS

• allows weighted acquire/release;
• supports cancellation via context;
• allows change semaphore limit after creation;
• faster than channel based semaphores.

Usage

Initiate

import "github.com/marusama/semaphore/v2"
...
sem := semaphore.New(5) // new semaphore with limit = 5

Acquire

sem.Acquire(ctx, n)     // acquire n with context
sem.TryAcquire(n)       // try acquire n without blocking 
...
ctx := context.WithTimeout(context.Background(), time.Second)
sem.Acquire(ctx, n)     // acquire n with timeout

Release

sem.Release(n)          // release n

Change semaphore limit

sem.SetLimit(new_limit) // set new semaphore limit

Some benchmarks

Run on MacBook Pro (2017) with 3,1GHz Core i5 cpu and 8GB DDR3 ram, macOS High Sierra, go version go1.11.4 darwin/amd64:

// this semaphore:
BenchmarkSemaphore_Acquire_Release_under_limit_simple-4                     20000000            98.6 ns/op        96 B/op          1 allocs/op
BenchmarkSemaphore_Acquire_Release_under_limit-4                             1000000          1593 ns/op         960 B/op         10 allocs/op
BenchmarkSemaphore_Acquire_Release_over_limit-4                               100000         20760 ns/op        9600 B/op        100 allocs/op


// some other implementations:

// golang.org/x/sync/semaphore:
BenchmarkXSyncSemaphore_Acquire_Release_under_limit_simple-4                50000000            34.9 ns/op         0 B/op          0 allocs/op
BenchmarkXSyncSemaphore_Acquire_Release_under_limit-4                        1000000          1103 ns/op           0 B/op          0 allocs/op
BenchmarkXSyncSemaphore_Acquire_Release_over_limit-4                           30000         65927 ns/op       15985 B/op        299 allocs/op

// github.com/abiosoft/semaphore:
BenchmarkAbiosoftSemaphore_Acquire_Release_under_limit_simple-4             10000000           208 ns/op           0 B/op          0 allocs/op
BenchmarkAbiosoftSemaphore_Acquire_Release_under_limit-4                      500000          3147 ns/op           0 B/op          0 allocs/op
BenchmarkAbiosoftSemaphore_Acquire_Release_over_limit-4                        50000         37148 ns/op           0 B/op          0 allocs/op

// github.com/dropbox/godropbox
BenchmarkDropboxBoundedSemaphore_Acquire_Release_under_limit_simple-4       20000000            75.9 ns/op         0 B/op          0 allocs/op
BenchmarkDropboxBoundedSemaphore_Acquire_Release_under_limit-4               2000000           629 ns/op           0 B/op          0 allocs/op
BenchmarkDropboxBoundedSemaphore_Acquire_Release_over_limit-4                 200000         27308 ns/op           0 B/op          0 allocs/op
BenchmarkDropboxUnboundedSemaphore_Acquire_Release_under_limit_simple-4     50000000            39.7 ns/op         0 B/op          0 allocs/op
BenchmarkDropboxUnboundedSemaphore_Acquire_Release_under_limit-4             1000000          1170 ns/op           0 B/op          0 allocs/op
BenchmarkDropboxUnboundedSemaphore_Acquire_Release_over_limit-4               100000         21013 ns/op           0 B/op          0 allocs/op

// github.com/kamilsk/semaphore
BenchmarkKamilskSemaphore_Acquire_Release_under_limit_simple-4              20000000           110 ns/op          16 B/op          1 allocs/op
BenchmarkKamilskSemaphore_Acquire_Release_under_limit-4                      1000000          1520 ns/op         160 B/op         10 allocs/op
BenchmarkKamilskSemaphore_Acquire_Release_over_limit-4                         50000         42693 ns/op        1600 B/op        100 allocs/op

// github.com/pivotal-golang/semaphore
BenchmarkPivotalGolangSemaphore_Acquire_Release_under_limit_simple-4         3000000           558 ns/op         136 B/op          2 allocs/op
BenchmarkPivotalGolangSemaphore_Acquire_Release_under_limit-4                 200000          9530 ns/op        1280 B/op         20 allocs/op
BenchmarkPivotalGolangSemaphore_Acquire_Release_over_limit-4                   10000        111264 ns/op       12801 B/op        200 allocs/op

You can rerun these benchmarks, just checkout benchmarks branch and run go test -bench=. -benchmem ./bench/...