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README.md
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@ -6,37 +6,99 @@
[![GoDoc](https://godoc.org/github.com/hibiken/asynq?status.svg)](https://godoc.org/github.com/hibiken/asynq)
[![Gitter chat](https://badges.gitter.im/go-asynq/gitter.svg)](https://gitter.im/go-asynq/community)
Simple and efficient asynchronous task processing library in Go.
Asynq is a simple Go library for queueing tasks and processing them in the background with workers.
It is backed by Redis and it is designed to have a low barrier to entry. It should be integrated in your web stack easily.
**Important Note**: Current major version is zero (v0.x.x) to accomodate rapid development and fast iteration while getting early feedback from users. The public API could change without a major version update before v1.0.0 release.
## Table of Contents
- [Overview](#overview)
- [Requirements](#requirements)
- [Installation](#installation)
- [Getting Started](#getting-started)
- [Command Line Tool](#command-line-tool)
- [Acknowledgements](#acknowledgements)
- [License](#license)
## Overview
![Gif](/docs/assets/asynqmon_stats.gif)
Package asynq provides a framework for asynchronous task processing.
## Installation
Asynq provides:
To install `asynq` library, run the following command:
- Clear separation of task producer and consumer
- Ability to process multiple tasks concurrently
- Ability to schedule task processing in the future
- Automatic retry of failed tasks with exponential backoff
- [Ability to configure](https://github.com/hibiken/asynq/wiki/Task-Retry) task retry count and retry delay
- Support for [priority queues](https://github.com/hibiken/asynq/wiki/Priority-Queues)
- [Unix signal handling](https://github.com/hibiken/asynq/wiki/Signals) to gracefully shutdown background processing
- [Automatic failover](https://github.com/hibiken/asynq/wiki/Automatic-Failover) using Redis sentinels
- [Command line tool](/tools/asynqmon/README.md) to query tasks for monitoring and troubleshooting purposes
```sh
go get -u github.com/hibiken/asynq
```
## Quick Start
First, make sure you are running a Redis server locally.
```sh
redis-server
```
To create and schedule tasks, use `Client` and provide a task and when to process the task.
```go
func main() {
r := &asynq.RedisClientOpt{
Addr: "localhost:6379",
}
client := asynq.NewClient(r)
// Create a task with task type 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 immediately
err := client.Schedule(t1, time.Now())
// Process 24 hrs later
err = client.Schedule(t2, time.Now().Add(24 * time.Hour))
// If processing fails, retry up to 10 times (Default is 25)
err = client.Schedule(t1, time.Now(), asynq.Retry(10))
// Use custom queue called "critical"
err = client.Schedule(t1, time.Now(), asynq.Queue("critical"))
}
```
To start the background workers, use `Background` and provide your `Handler` to process the tasks.
```go
func main() {
r := &asynq.RedisClientOpt{
Addr: "localhost:6379",
}
bg := asynq.NewBackground(r, &asynq.Config{
// Specify how many concurrent workers to use
Concurrency: 10,
// You can optionally create multiple queues
// with different priority level
Queues: map[string]uint{
"critical": 6,
"default": 3,
"low": 1,
},
// See the godoc for other configuration options
})
bg.Run(handler)
}
```
`Handler` is an interface with one method `ProcessTask` with the following signature.
```go
// 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 after delay.
type Handler interface {
ProcessTask(*Task) error
}
```
For a more detailed walk-through of the library, see our [Getting Started Guide](https://github.com/hibiken/asynq/wiki/Getting-Started).
To Learn more about `asynq` features and APIs, see our [Wiki pages](https://github.com/hibiken/asynq/wiki) and [godoc](https://godoc.org/github.com/hibiken/asynq).
## Requirements
@ -45,263 +107,6 @@ Asynq provides:
| [Redis](https://redis.io/) | v2.8+ |
| [Go](https://golang.org/) | v1.12+ |
## Installation
To install both `asynq` library and `asynqmon` command line tool, run the following command:
```
go get -u github.com/hibiken/asynq
go get -u github.com/hibiken/asynq/tools/asynqmon
```
## Getting Started
In this quick tour of `asynq`, we are going to create two programs.
- `producer.go` will create and schedule tasks to be processed asynchronously by the consumer.
- `consumer.go` will process the tasks created by the producer.
**This guide assumes that you are running a Redis server at `localhost:6379`**.
Before we start, make sure you have Redis installed and running.
The first thing we need to do is create two main files.
```sh
mkdir producer consumer
touch producer/producer.go consumer/consumer.go
```
Import `asynq` in both files.
```go
import "github.com/hibiken/asynq"
```
Asynq uses Redis as a message broker.
Use one of `RedisConnOpt` types to specify how to connect to Redis.
We are going to use `RedisClientOpt` here.
```go
// both in producer.go and consumer.go
var redis = &asynq.RedisClientOpt{
Addr: "localhost:6379",
// Omit if no password is required
Password: "mypassword",
// Use a dedicated db number for asynq.
// By default, Redis offers 16 databases (0..15)
DB: 0,
}
```
In `producer.go`, we are going to create a `Client` instance to create and schedule tasks.
In `asynq`, a unit of work to be performed is encapsluated in a struct called `Task`.
Which has two fields: `Type` and `Payload`.
```go
// Task represents a task to be performed.
type Task struct {
// Type indicates the type of task to be performed.
Type string
// Payload holds data needed to perform the task.
Payload Payload
}
```
To create a task, use `NewTask` function and pass type and payload for the task.
You schedule a task by calling `Client.Schedule` passing in the task and the timethe task neeeds to be processed.
```go
// producer.go
func main() {
client := asynq.NewClient(redis)
// 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())
if err != nil {
log.Fatal(err)
}
// Process the task 24 hours later.
err = client.Schedule(t2, time.Now().Add(24 * time.Hour))
if err != nil {
log.Fatal(err)
}
}
```
In `consumer.go`, create a `Background` instance to process the tasks.
`NewBackground` function takes `RedisConnOpt` and `Config`.
You can take a look at documentation on `Config` to see the available options.
We are only going to specify the concurrency in this example.
```go
// consumer.go
func main() {
bg := asynq.NewBackground(redis, &asynq.Config{
Concurrency: 10,
})
bg.Run(handler)
}
```
The argument to `(*asynq.Background).Run` is an interface `asynq.Handler` which has one method `ProcessTask`.
```go
// 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`.
```go
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 User %d\n", id)
case "send_reminder_email":
id, err := t.Payload.GetInt("user_id")
if err != nil {
return err
}
fmt.Printf("Send Reminder Email to User %d\n", id)
default:
return fmt.Errorf("unexpected task type: %s", t.Type)
}
return nil
}
func main() {
bg := asynq.NewBackground(redis, &asynq.Config{
Concurrency: 10,
})
// Use asynq.HandlerFunc adapter for a handler function
bg.Run(asynq.HandlerFunc(handler))
}
```
We could keep adding cases to this handler function, but in a realistic application, it's convenient to define the logic for each case in a separate function.
To refactor our code, let's create a simple dispatcher which maps task type to its handler.
```go
// consumer.go
// Dispatcher is used to dispatch tasks to registered handlers.
type Dispatcher struct {
mapping map[string]asynq.HandlerFunc
}
// HandleFunc registers a task handler
func (d *Dispatcher) HandleFunc(taskType string, fn asynq.HandlerFunc) {
d.mapping[taskType] = fn
}
// ProcessTask processes a task.
//
// NOTE: Dispatcher satisfies asynq.Handler interface.
func (d *Dispatcher) ProcessTask(task *asynq.Task) error {
fn, ok := d.mapping[task.Type]
if !ok {
return fmt.Errorf("no handler registered for %q", task.Type)
}
return fn(task)
}
func main() {
d := &Dispatcher{mapping: make(map[string]asynq.HandlerFunc)}
d.HandleFunc("send_welcome_email", sendWelcomeEmail)
d.HandleFunc("send_reminder_email", sendReminderEmail)
bg := asynq.NewBackground(redis, &asynq.Config{
Concurrency: 10,
})
bg.Run(d)
}
func sendWelcomeEmail(t *asynq.Task) error {
id, err := t.Payload.GetInt("user_id")
if err != nil {
return err
}
fmt.Printf("Send Welcome Email to User %d\n", id)
return nil
}
func sendReminderEmail(t *asynq.Task) error {
id, err := t.Payload.GetInt("user_id")
if err != nil {
return err
}
fmt.Printf("Send Welcome Email to User %d\n", id)
return nil
}
```
Now that we have both task producer and consumer, we can run both programs.
```sh
go run producer.go
```
This will create two tasks: One that should processed immediately and another to be processed 24 hours later.
Let's use `asynqmon` tool to inspect the tasks.
```sh
asynqmon stats
```
You should able to see that there's one task in **Enqueued** state and another in **Scheduled** state.
Note: To understand the meaning of each state, see [Life of a Task](https://github.com/hibiken/asynq/wiki/Life-of-a-Task) on our Wiki page.
Let's run `asynqmon` with `watch` command so that we can continuously run the command to see the changes.
```sh
watch -n 3 asynqmon stats # Runs `asynqmon stats` every 3 seconds
```
And finally, let's start the consumer program to process scheduled tasks.
```sh
go run consumer.go
```
**Note**: This will not exit until you send a signal to terminate the program. See [Signal Wiki page](https://github.com/hibiken/asynq/wiki/Signals) for best practice on how to safely terminate background processing.
You should be able to see text printed in your terminal indicating that the task was processed successfully.
This was a whirlwind tour of `asynq` basics. To learn more about all of its features such as **[priority queues](https://github.com/hibiken/asynq/wiki/Priority-Queues)** and **[custom retry](https://github.com/hibiken/asynq/wiki/Task-Retry)**, see our [Wiki page](https://github.com/hibiken/asynq/wiki).
## Command Line Tool
Asynq ships with a command line tool to inspect the state of queues and tasks.

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tools/asynqmon/README.md
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@ -65,7 +65,7 @@ Example:
asynqmon ls retry
asynqmon ls scheduled
asynqmon ls dead
asynqmon ls enqueued
asynqmon ls enqueued:default
asynqmon ls inprogress
### Enqueue