README

run

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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 concurrently runs all of the actors, waits until the first actor exits, invokes the interrupt functions, and finally returns control to the caller only once all actors have returned. 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.

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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

    Examples

    Constants

    This section is empty.

    Variables

    This section is empty.

    Functions

    func SignalHandler

    func SignalHandler(ctx context.Context, signals ...os.Signal) (execute func() error, interrupt func(error))

      SignalHandler returns an actor, i.e. an execute and interrupt func, that terminates with SignalError when the process receives one of the provided signals, or the parent context is canceled.

      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.

          Example (Basic)
          Output:
          
          The second actor is returning immediately
          The first actor was interrupted with: immediate teardown
          The second actor was interrupted with: immediate teardown
          The first actor was canceled
          The group was terminated with: immediate teardown
          
          Example (Context)
          Output:
          
          The group was terminated with: context canceled
          
          Example (Listener)
          Output:
          
          http.Serve returned
          The group was terminated with: immediate teardown
          

          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.

            type SignalError

            type SignalError struct {
            	Signal os.Signal
            }

              SignalError is returned by the signal handler's execute function when it terminates due to a received signal.

              func (SignalError) Error

              func (e SignalError) Error() string

                Error implements the error interface.

                Source Files