README graceful goroutine orchestration



While Go provides goroutines, channels and selects as first-class citizens to support concurrent programming, it is not trivial to combine these elements to address important concerns of goroutine orchestration, e.g. error handling, panic recovery, goroutine leak prevention, goroutine reuse, goroutine throttle and logging.

The package provides a mini-framework to address those cross-cutting concerns.

Quick start
go get -u

Here is an example illustrating the usage of the goroutine pool and the group. The task is described in the "Google Search 2.0" page from this slide.

// the goroutine pool
pool := gopool.NewGoroutinePool(
	gopool.Max(8),                // the pool contains maximum 8 goroutines
	gopool.IdleTime(time.Minute), // a goroutine will stay in idle for maximum 1 minute before exiting

// the group
// the goroutine pool might have longer lifespan than the group
group := gopool.NewGroup(
	context.Background(), // a context that can cancel the whole group
	gopool.Pool(pool),       // the goroutine pool used by the group
	gopool.Recover(true),    // recover from panic and returns the PanicError
	gopool.Log(func(info *gopool.LogInfo) { // a log function for all starts/stops

searches := []*GoogleSearch{
	{Search: Web, Query: "golang"},
	{Search: Image, Query: "golang"},
	{Search: Video, Query: "golang"},
for _, search := range searches {
	// start searching in parallel
	if err := group.Go(search); err != nil {

// wait for all searches stop
if err := group.Wait(); err != nil {

for _, search := range searches {

See the full example here.


The package is built around the concept of a runner.

type Runner interface {
	Run(context.Context) error

Correct implementation of a runner should satisfy the following conditions:

  • blocks when the work is on going
  • returns when all work is done, an error occurred or context is cancelled

With goroutine pool and group in the package, the user does not need to use the go statement explicitly, but only needs to implement their objects satisfying the Runner interface.

A Group is useful when multiple concurrent sub-tasks needed to be combined as a single task (the task failed when one of them failed, every sub-task should be cancelled when the task is cancelled).

A Pool is useful when there are many short-lived goroutines.

A group can be built upon a pool, not vice versa.



    Package run provides graceful goroutine orchestration.



    This section is empty.


    View Source
    var ErrClosed = errors.New("run.Closer: already closed")

      ErrClosed is returned when the Closer is already closed


      func Closer

      func Closer(runner Runner) io.Closer

        Closer wraps a Runner into a Closer, whose Close method will cancel the runner and wait for its exit and return its error

        func WaitCloser

        func WaitCloser(runner Runner) io.Closer

          WaitCloser wraps a Runner into a Closer, whose Close method will wait for the runner to exit and return its error


          type Func

          type Func func(context.Context) error

            The Func type is an adapter to allow the use of ordinary functions as runners. If f is a function with the appropriate signature, Func(f) is a Runner that calls f.

            func (Func) Run

            func (f Func) Run(ctx context.Context) error

              Run calls f(ctx)

              type Group

              type Group struct {
              	// contains filtered or unexported fields

                A Group is an error group that cancels the context on error, without all those options

                modified from

                func NewGroup

                func NewGroup(ctx context.Context) *Group

                  NewGroup creates a new GroupGroup

                  func (*Group) Cancel

                  func (g *Group) Cancel()

                    Cancel cancels the group

                    func (*Group) Go

                    func (g *Group) Go(runner Runner)

                      Go runs the given runner in a goroutine

                      func (*Group) Wait

                      func (g *Group) Wait() error

                        Wait waits for all goroutines exit and returns the first returned error

                        type Runner

                        type Runner interface {
                        	Run(context.Context) error

                          Runner defines the Run method to be exeucuted within a goroutine


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