README
¶
async.go
Status: EXPERIMENTAL
This library is primarily intended as a directed learning exercise and eventual collection of utilities and patterns for working asynchronously in Go.
Documentation
Full go doc style documentation for the project can be viewed online without
installing this package by using the excellent GoDoc site here:
http://godoc.org/github.com/41north/async.go
You can also view the documentation locally once the package is installed with
the godoc tool by running godoc -http=":6060" and pointing your browser to
http://localhost:6060/pkg/github.com/41north/async.go
Installation
$ go get -u github.com/41north/async.go
Add this import line to the file you're working in:
import "github.com/41north/async.go"
Quick Start
Future
A basic example:
// create a string future
f := NewFuture[string]()
// create a consumer channel
ch := f.Get()
go func() {
println(fmt.Sprintf("Value: %s", <-ch))
}()
// set the value
f.Set("hello")
Counting Semaphore
A basic example:
// we create an input and output channel for work needing to be done
inCh := make(chan string, 128)
outCh := make(chan int, 128)
// we want a max of 10 in-flight processes
s := NewCountingSemaphore(10)
// we create more workers than tokens available
for i := 0; i < 100; i++ {
go func() {
for {
// acquire a token, waiting until one is available
s.Acquire(1)
// consume from the input channel
v, ok := <-inCh
if !ok {
// channel was closed
return
}
// do some work and produce an output value
outCh <- len(v)
// you need to be careful about releasing, if possible perform it with defer
s.Release(1)
}
}()
}
// generate some work and put it into the work queue
// ...
// ...
There are more examples available in the go doc.
License
Go-async is licensed under the Apache 2.0 License
Contact
If you want to get in touch drop us an email at [email protected]
Documentation
¶
Overview ¶
Package async provides constructs for various asynchronous patterns.
Index ¶
Examples ¶
Constants ¶
const (
PanicSetOnImmediateFuture = "you cannot set a value on an immediate future"
)
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type CountingSemaphore ¶
type CountingSemaphore interface {
// Size returns the total number of tokens available withing this CountingSemaphore.
Size() int32
// Acquire attempts to acquire an amount of tokens from the semaphore, waiting until it is successful.
Acquire(count int32)
// TryAcquire attempts to acquire an amount of tokens from the semaphore and returns whether
// it was successful or not.
TryAcquire(count int32) bool
// Release attempts to return a certain amount of tokens to the semaphore, waiting until it is successful.
Release(count int32)
// TryRelease attempts to return a certain amount of tokens to the semaphore and returns whether
// it was successful or not.
TryRelease(count int32) bool
}
CountingSemaphore can be used to limit the amount of in-flight processes / tasks.
Example ¶
// we create an input and output channel for work needing to be done
inCh := make(chan string, 128)
outCh := make(chan int, 128)
// we want a max of 10 in-flight processes
s := async.NewCountingSemaphore(10)
// we create more workers than tokens available
for i := 0; i < 100; i++ {
go func() {
for {
// acquire a token, waiting until one is available
s.Acquire(1)
// consume from the input channel
v, ok := <-inCh
if !ok {
// channel was closed
return
}
// do some work and produce an output value
outCh <- len(v)
// you need to be careful about releasing, if possible perform it with defer
s.Release(1)
}
}()
}
// generate some work and put it into the work queue
// ...
// ...
func NewCountingSemaphore ¶
func NewCountingSemaphore(size int32) CountingSemaphore
NewCountingSemaphore creates a new semaphore with specified amount of available tokens.
type Future ¶
type Future[T any] interface { // Get returns a response channel of size 1 for receiving the future value. // If the value has already been set it will already be available within the return channel. Get() <-chan T // Set sets the return value and notifies consumers. Consumers are notified once only, // with the return value indicating if Set was successful or not. Set(value T) bool }
Future represents a value of type T that will be set at some time in the future.
Example (Basic) ¶
// create a string future
f := async.NewFuture[string]()
// create a consumer channel
ch := f.Get()
go func() {
println(fmt.Sprintf("Value: %s", <-ch))
}()
// set the value
f.Set("hello")
Example (Multiple) ¶
// create some futures
foo := async.NewFuture[string]()
bar := async.NewFuture[string]()
// compute in the background
go func() {
foo.Set("foo")
}()
go func() {
foo.Set("bar")
}()
// wait for their results
println(<-foo.Get())
println(<-bar.Get())
Example (Select) ¶
// create some futures
foo := async.NewFuture[string]()
bar := async.NewFuture[string]()
// compute their values in the background
go func() {
foo.Set("foo")
}()
go func() {
bar.Set("bar")
}()
// create some consumer channels
fooCh := foo.Get()
barCh := bar.Get()
// wait with timeout
ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
defer cancel()
var result []string
finished := false
for {
select {
case <-ctx.Done():
fmt.Println("timeout")
finished = true
case v, ok := <-fooCh:
if ok {
result = append(result, v)
}
finished = len(result) == 2
case v, ok := <-barCh:
if ok {
result = append(result, v)
}
finished = len(result) == 2
}
if finished {
// break out of the loop
break
}
}
// print all the results
fmt.Println(result)
func NewFutureImmediate ¶
NewFutureImmediate creates a future of type T that has a value that is already set.
Example ¶
f := async.NewFutureImmediate("hello")
println(<-f.Get())
type Result ¶
type Result[T any] interface { // Unwrap deconstructs the contents of this Result into a tuple. Unwrap() (T, error) }
Result is a simple wrapper for representing a value or an error.
func NewResult ¶
NewResult creates a result instance with a provided value and error. It's sometimes more convenient to instantiate like this when implementing library code.
Example ¶
result := async.NewResultValue[string]("success")
v, _ := result.Unwrap()
println(v)
func NewResultErr ¶
NewResultErr creates a failed result.
Example ¶
result := async.NewResultErr[string](errors.New("failure"))
_, err := result.Unwrap()
panic(err)
func NewResultValue ¶
NewResultValue creates a successful result.
Source Files