asynq/README.md

Asynq 

Simple, efficent asynchronous task processing library in Go.

Table of Contents

• Overview
• Requirements
• Installation
• Getting Started
• License

Overview

Asynq provides a simple interface to asynchronous task processing.

Asynq also ships with a CLI to monitor the queues and take manual actions if needed.

Asynq provides:

• Clear separation of task producer and consumer
• Ability to schedule task processing in the future
• Automatic retry of failed tasks with exponential backoff
• Ability to configure max retry count per task
• Ability to configure max number of worker goroutines to process tasks
• Unix signal handling to safely shutdown background processing
• Enhanced reliability TODO(hibiken): link to wiki page describing this.
• CLI to query and mutate queues state for mointoring and administrative purposes

Requirements

Dependency	Version
Redis	v2.6+
Go	v1.12+
github.com/go-redis/redis	v.7.0+

Installation

go get github.com/hibiken/asynq

Getting Started

1. Import asynq in your file.

import "github.com/hibiken/asynq"

2. Create a Client instance to create tasks.

func main() {
    r := redis.NewClient(&redis.Options{
        Addr: "localhost:6379",
    }
    client := asynq.NewClient(r)

    // create a task with typename and payload.
    t1 := asynq.NewTask(
        "send_welcome_email",
        map[string]interface{}{"user_id": 42})

    t2 := asynq.NewTask(
        "send_reminder_email",
        map[string]interface{}{"user_id": 42})

    // process the task immediately.
    err := client.Schedule(t1, time.Now())

    // process the task 24 hours later.
    err = client.Schedule(t2, time.Now().Add(24 * time.Hour))

    // specify the max number of retry (default: 25)
    err = client.Schedule(t1, time.Now(), asynq.MaxRetry(1))
}

3. Create a Background instance to process tasks.

func main() {
    r := redis.NewClient(&redis.Options{
        Addr: "localhost:6379",
    }
    bg := asynq.NewBackground(r, &asynq.Config{
        Concurrency: 20,
    })

    // Blocks until signal TERM or INT is received.
    // For graceful shutdown, send signal TSTP to stop processing more tasks
    // before sending TERM or INT signal.
    bg.Run(handler)
}

The argument to (*asynq.Background).Run is an interface asynq.Handler which has one method ProcessTask.

// ProcessTask should return nil if the processing of a task
// is successful.
//
// If ProcessTask return a non-nil error or panics, the task
// will be retried.
type Handler interface {
    ProcessTask(*Task) error
}

The simplest way to implement a handler is to define a function with the same signature and use asynq.HandlerFunc adapter type when passing it to Run.

func handler(t *asynq.Task) error {
    switch t.Type {
    case "send_welcome_email":
        id, err := t.Payload.GetInt("user_id")
        if err != nil {
            return err
        }
        fmt.Printf("Send Welcome Email to %d\n", id)

    // ... handle other types ...

    default:
        return fmt.Errorf("unexpected task type: %s", t.Type)
    }
    return nil
}

func main() {
    r := redis.NewClient(&redis.Options{
        Addr: "localhost:6379",
    }
    bg := asynq.NewBackground(r, &asynq.Config{
        Concurrency: 20,
    })

    // Use asynq.HandlerFunc adapter for a handler function
    bg.Run(asynq.HandlerFunc(handler))
}

License

Asynq is released under the MIT license. See LICENSE.