Taskrunner

Background

Package taskrunner provides an API for running concurrent tasks in a promise-like style without having to deal with concurrency directly.

The library provides an interface that must be implemented to run a Task concurrently and a concurrency-safe API for running tasks concurrently without managing the channels, goroutines and waitgroups yourself.

Note that using the library is generally less efficient than using Go's concurrency primitives directly. This library hopes to provide code reuse with access to concurrency without having to reimplement the same channel patterns over and over again.

Using TaskRunner

To use Taskrunner, you'll need some setup. Define a struct that implements the Task interface to use as the payload to Run.

One example of a naive Task could be something like sending emails.

type EmailPayload struct {
    Email string
    Message string
}

func (p *EmailPayload) Task(ctx context.Context) (interface{}, error) {
    if err := p.sendEmail(); err != nil {
        return nil, err
    }

    return nil, nil
}

func (p *EmailPayload) sendEmail() error {
    // send email
    // ...
    // check and return errors
}

Once you've implemented the Task, running the Task is as simple as creating a new Taskrunner, starting it and running your Task.

Run returns a function closure over the result of your Task so that you can retrieve it at a later time. Run accepts a context and passes it to your task so that you can control the deadline of your Task and even pass request-scoped items via the context.

// Configure the number of workers using a functional option.
runner, err := taskrunner.NewTaskRunner(taskrunner.OptionMaxGoroutines(runtime.NUMCPU + 1))
if err != nil {
    panic(err.Error())
}

// Start the runner.
if err := runner.Start(); err != nil {
    panic(err.Error())
}

// Get your promise.
promise := runner.Run(context.TODO(), &EmailPayload{
    Email: "...",
    Message: "...",
}})

// Check the result of your promise.
if _, err := promise(); err != nil {
    log.Errorf("sending email failed - err=%+v", err)
}

Examples

See the examples directory for some codified example usages of taskrunner.

• helloworld shows how to run simple Tasks with no return value.
• helloworld shows how to run simple Tasks with a return value and possible error state. Shows how to use the promises and how to perform a type assertion to safely check the return value.
• expvar includes an example of accessing the metric hooks available via the Option functions and uses expvar to demonstrate.