run

README

run

run.Group is a universal mechanism to manage goroutine lifecycles.

Create a zero-value run.Group, and then add actors to it. Actors are defined as a pair of functions: an execute function, which should run synchronously; and an interrupt function, which, when invoked, should cause the execute function to return. Finally, invoke Run, which blocks until the first actor returns. This general-purpose API allows callers to model pretty much any runnable task, and achieve well-defined lifecycle semantics for the group.

run.Group was written to manage component lifecycles in func main for OK Log. But it's useful in any circumstance where you need to orchestrate multiple goroutines as a unit whole. Click here to see a video of a talk where run.Group is described.

Examples

context.Context

ctx, cancel := context.WithCancel(context.Background())
g.Add(func() error {
	return myProcess(ctx, ...)
}, func(error) {
	cancel()
})

net.Listener

ln, _ := net.Listen("tcp", ":8080")
g.Add(func() error {
	return http.Serve(ln, nil)
}, func(error) {
	ln.Close()
})

io.ReadCloser

var conn io.ReadCloser = ...
g.Add(func() error {
	s := bufio.NewScanner(conn)
	for s.Scan() {
		println(s.Text())
	}
	return s.Err()
}, func(error) {
	conn.Close()
})

Comparisons

Package run is somewhat similar to package errgroup, except it doesn't require actor goroutines to understand context semantics.

It's somewhat similar to package tomb.v1 or tomb.v2, except it has a much smaller API surface, delegating e.g. staged shutdown of goroutines to the caller.

Documentation

Overview

Package run implements an actor-runner with deterministic teardown. It is somewhat similar to package errgroup, except it does not require actor goroutines to understand context semantics. This makes it suitable for use in more circumstances; for example, goroutines which are handling connections from net.Listeners, or scanning input from a closable io.Reader.

Index

• type Group
  • func (g *Group) Add(execute func() error, interrupt func(error))
  • func (g *Group) Run() error

Types

type Group

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

Group collects actors (functions) and runs them concurrently. When one actor (function) returns, all actors are interrupted. The zero value of a Group is useful.

func (*Group) Add

func (g *Group) Add(execute func() error, interrupt func(error))

Add an actor (function) to the group. Each actor must be pre-emptable by an interrupt function. That is, if interrupt is invoked, execute should return. Also, it must be safe to call interrupt even after execute has returned.

The first actor (function) to return interrupts all running actors. The error is passed to the interrupt functions, and is returned by Run.

func (*Group) Run

func (g *Group) Run() error

Run all actors (functions) concurrently. When the first actor returns, all others are interrupted. Run only returns when all actors have exited. Run returns the error returned by the first exiting actor.