hunch

Hunch

Hunch provides functions like: All, First, Retry, Waterfall etc., that makes asynchronous flow control more intuitive.

About Hunch

Go have several concurrency patterns, here're some articles:

• https://blog.golang.org/pipelines
• https://blog.golang.org/context
• https://blog.golang.org/go-concurrency-patterns-timing-out-and
• https://blog.golang.org/advanced-go-concurrency-patterns

But nowadays, using the context package is the most powerful pattern.

So base on context, Hunch provides functions that can help you deal with complex asynchronous logics with ease.

Usage

Installation

go get

$ go get -u -v github.com/aaronjan/hunch

go mod (Recommended)

import "github.com/aaronjan/hunch"

$ go mod tidy

Types

type Executable func(context.Context) (interface{}, error)

type ExecutableInSequence func(context.Context, interface{}) (interface{}, error)

API

All

func All(parentCtx context.Context, execs ...Executable) ([]interface{}, error) 

All returns all the outputs from all Executables, order guaranteed.

ctx := context.Background()
r, err := hunch.All(
    ctx,
    func(ctx context.Context) (interface{}, error) {
        time.Sleep(300 * time.Millisecond)
        return 1, nil
    },
    func(ctx context.Context) (interface{}, error) {
        time.Sleep(200 * time.Millisecond)
        return 2, nil
    },
    func(ctx context.Context) (interface{}, error) {
        time.Sleep(100 * time.Millisecond)
        return 3, nil
    },
)

fmt.Println(r, err)
// Output:
// [1 2 3] <nil>

Take

func Take(parentCtx context.Context, num int, execs ...Executable) ([]interface{}, error)

Take returns the first num values outputted by the Executables.

ctx := context.Background()
r, err := hunch.Take(
    ctx,
    // Only need the first 2 values.
    2,
    func(ctx context.Context) (interface{}, error) {
        time.Sleep(300 * time.Millisecond)
        return 1, nil
    },
    func(ctx context.Context) (interface{}, error) {
        time.Sleep(200 * time.Millisecond)
        return 2, nil
    },
    func(ctx context.Context) (interface{}, error) {
        time.Sleep(100 * time.Millisecond)
        return 3, nil
    },
)

fmt.Println(r, err)
// Output:
// [3 2] <nil>

Last

func Last(parentCtx context.Context, num int, execs ...Executable) ([]interface{}, error)

Last returns the last num values outputted by the Executables.

ctx := context.Background()
r, err := hunch.Last(
    ctx,
    // Only need the last 2 values.
    2,
    func(ctx context.Context) (interface{}, error) {
        time.Sleep(300 * time.Millisecond)
        return 1, nil
    },
    func(ctx context.Context) (interface{}, error) {
        time.Sleep(200 * time.Millisecond)
        return 2, nil
    },
    func(ctx context.Context) (interface{}, error) {
        time.Sleep(100 * time.Millisecond)
        return 3, nil
    },
)

fmt.Println(r, err)
// Output:
// [2 1] <nil>

Waterfall

func Waterfall(parentCtx context.Context, execs ...ExecutableInSequence) (interface{}, error)

Waterfall runs ExecutableInSequences one by one, passing previous result to next Executable as input. When an error occurred, it stop the process then returns the error. When the parent Context canceled, it returns the Err() of it immediately.

ctx := context.Background()
r, err := hunch.Waterfall(
    ctx,
    func(ctx context.Context, n interface{}) (interface{}, error) {
        return 1, nil
    },
    func(ctx context.Context, n interface{}) (interface{}, error) {
        return n.(int) + 1, nil
    },
    func(ctx context.Context, n interface{}) (interface{}, error) {
        return n.(int) + 1, nil
    },
)

fmt.Println(r, err)
// Output:
// 3 <nil>

Retry

func Retry(parentCtx context.Context, retries int, fn Executable) (interface{}, error)

Retry attempts to get a value from an Executable instead of an Error. It will keeps re-running the Executable when failed no more than retries times. Also, when the parent Context canceled, it returns the Err() of it immediately.

count := 0
getStuffFromAPI := func() (int, error) {
    if count == 5 {
        return 1, nil
    }
    count++

    return 0, fmt.Errorf("timeout")
}

ctx := context.Background()
r, err := hunch.Retry(
    ctx,
    10,
    func(ctx context.Context) (interface{}, error) {
        rs, err := getStuffFromAPI()

        return rs, err
    },
)

fmt.Println(r, err, count)
// Output:
// 1 <nil> 5

Credits

Heavily inspired by Async and ReactiveX.

Licence

Apache 2.0