runner

README

What Is It ?

An utility package to allow run groups : one group fails, all peers are shutdown.

Used in gracefully shutdown multiple components that should not know each other.

Documentation

Index

• type Erroer
• type Group
  • func (g *Group) Add(execute Runner, interrupt Erroer)
  • func (g *Group) Wait(ctx context.Context, cancel context.CancelFunc) error
• type Runner

Examples

• Group.Add (Basic)
• Group.Add (Context)
• Group.Add (Listener)

Types

type Erroer

type Erroer func(error)

type Group

type Group struct {
	// contains filtered or unexported fields
}

func (*Group) Add

func (g *Group) Add(execute Runner, interrupt Erroer)

Example (Basic)

package main

import (
	"context"
	"errors"
	"fmt"
	"time"

	"github.com/badu/wg-cc/pkg/runner"
)

func main() {
	var g runner.Group
	{
		cancel := make(chan struct{})
		g.Add(func() error {
			select {
			case <-time.After(time.Second):
				fmt.Printf("The first funcPair had its time elapsed\n")
				return nil
			case <-cancel:
				fmt.Printf("The first funcPair was canceled\n")
				return nil
			}
		}, func(err error) {
			fmt.Printf("The first funcPair was interrupted with: %v\n", err)
			close(cancel)
		})
	}
	{
		g.Add(func() error {
			fmt.Printf("The second funcPair is returning immediately\n")
			return errors.New("immediate teardown")
		}, func(err error) {
			// Note that this interrupt function is called, even though the
			// corresponding execute function has already returned.
			fmt.Printf("The second funcPair was interrupted with: %v\n", err)
		})
	}
	ctx, cancel := context.WithCancel(context.Background())
	fmt.Printf("The group was terminated with: %v\n", g.Wait(ctx, cancel))
}

Output:

The second funcPair is returning immediately
The first funcPair was interrupted with: immediate teardown
The second funcPair was interrupted with: immediate teardown
The first funcPair was canceled
The group was terminated with: immediate teardown

Example (Context)

package main

import (
	"context"
	"fmt"

	"github.com/badu/wg-cc/pkg/runner"
)

func main() {
	ctx, cancel := context.WithCancel(context.Background())
	var g runner.Group
	{
		ctx, cancel := context.WithCancel(ctx) // note: shadowed
		g.Add(func() error {
			return runUntilCanceled(ctx)
		}, func(error) {
			cancel()
		})
	}
	go cancel()
	fmt.Printf("The group was terminated with: %v\n", g.Wait(ctx, cancel))
}

func runUntilCanceled(ctx context.Context) error {
	<-ctx.Done()
	return ctx.Err()
}

Output:

The group was terminated with: context done

Example (Listener)

package main

import (
	"context"
	"errors"
	"fmt"
	"net"
	"net/http"

	"github.com/badu/wg-cc/pkg/runner"
)

func main() {
	var g runner.Group
	{
		ln, _ := net.Listen("tcp", ":0")
		g.Add(func() error {
			defer fmt.Printf("http.Serve returned\n")
			return http.Serve(ln, http.NewServeMux())
		}, func(error) {
			ln.Close()
		})
	}
	{
		g.Add(func() error {
			return errors.New("immediate teardown")
		}, func(error) {
			//
		})
	}

	ctx, cancel := context.WithCancel(context.Background())
	fmt.Printf("The group was terminated with: %v\n", g.Wait(ctx, cancel))
}

Output:

http.Serve returned
The group was terminated with: immediate teardown

func (*Group) Wait

func (g *Group) Wait(ctx context.Context, cancel context.CancelFunc) error

type Runner

type Runner func() error