bokchoy

Introduction

Bokchoy is a simple Go library for queueing tasks and processing them in the background with workers. It should be integrated in your web stack easily and it's designed to have a low barrier entry for newcomers.

It currently only supports Redis (client, sentinel and cluster) with some Lua magic, but internally it relies on a generic broker implementation to extends it.

Motivation

It's relatively easy to make a producer/receiver system in Go since the language contains builtins features to build it from scratch but we keep adding the same system everywhere instead of thinking reusable.

Bokchoy is a plug and play component, it does its job and it does it well for you that you can focus on your business logic.

Features

• Lightweight
• A Simple API close to net/http - if you already use net/http then you can learn it pretty quickly
• Designed with a modular/composable APIs - middlewares, queue middlewares
• Context control - built on context package, providing value chaining, cancelations and timeouts
• Highly configurable - tons of options to swap internal parts (broker, logger, timeouts, etc), if you cannot customize something then an option is missing
• Extensions - RPC server powered by gRPC, Sentry, etc.

Getting started

First, run a Redis server, of course:

redis-server

Define your producer which will send tasks:

package main

import (
	"context"
	"fmt"
	"log"

	"github.com/thoas/bokchoy"
)

func main() {
	ctx := context.Background()

	// define the main engine which will manage queues
	engine, err := bokchoy.NewDefault(ctx, "redis://localhost:6379")
	if err != nil {
		log.Fatal(err)
	}

	payload := map[string]string{
		"data": "hello world",
	}

	task, err := engine.Queue("tasks.message").Publish(ctx, payload)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Println(task, "has been published")
}

See producer directory for more information and to run it.

Now we have a producer which can send tasks to our engine, we need a worker to process them in the background:

package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"os/signal"

	"github.com/thoas/bokchoy"
)

func main() {
	ctx := context.Background()

	engine, err := bokchoy.NewDefault(ctx, "redis://localhost:6379")
	if err != nil {
		log.Fatal(err)
	}

	engine.Queue("tasks.message").HandleFunc(func(r *bokchoy.Request) error {
		fmt.Println("Receive request", r)
		fmt.Println("Payload:", r.Task.Payload)

		return nil
	})

	c := make(chan os.Signal, 1)
	signal.Notify(c, os.Interrupt)

	go func() {
		for range c {
			log.Print("Received signal, gracefully stopping")
			engine.Stop(ctx)
		}
	}()

	engine.Run(ctx)
}

A worker is defined by handlers, to define a Handler you have to follow this interface:

type Handler interface {
	Handle(*Request) error
}

You can create your own struct which implements this interface or use the HandlerFunc to generate a Handler from your function.

See worker directory for more information and to run it.

If you want a complete application example, you can read A Tour of Bokchoy which explain how to use the main features of it.

Installation

Using Go Modules

go get github.com/thoas/bokchoy

Advanced topics

Delayed tasks

When publishing a task, it will be immediately processed by the worker if it's not already occupied, you may want to delay the task on some occasions by using bokchoy.WithCountdown option:

payload := map[string]string{
    "data": "hello world",
}

queue.Publish(ctx, payload, bokchoy.WithCountdown(5*time.Second))

This task will be executed in 5 seconds.

Priority tasks

A task can be published at front of others by providing a negative countdown.

payload := map[string]string{
    "data": "hello world",
}

queue.Publish(ctx, payload, bokchoy.WithCountdown(-1))

This task will be published and processed immediately.

Custom instantiation

bokchoy.NewDefault allows simple instantiation when you have a simple setup. You may want to have more control over your setup. This allows you to use a customer serializer, custom logger, etc. Use bokchoy.New to do this:

bokchoy.New(ctx, bokchoy.Config{
    Broker: bokchoy.BrokerConfig{
        Type: "redis",
        Redis: bokchoy.RedisConfig{
            Type: "client",
            Client: bokchoy.RedisClientConfig{
                Addr: "localhost:6379",
            },
        },
    },
})

Note: bokchoy.NewDefault uses redis.ParseURL internally so it can handle connection strings like redis://user:pass@host:port/db without the need for bokchoy.New.

Custom serializer

By default the task serializer is JSON, you can customize it when initializing the Bokchoy engine, it must respect the Serializer interface.

bokchoy.New(ctx, bokchoy.Config{
    Broker: bokchoy.BrokerConfig{
        Type: "redis",
        Redis: bokchoy.RedisConfig{
            Type: "client",
            Client: bokchoy.RedisClientConfig{
                Addr: "localhost:6379",
            },
        },
    },
}, bokchoy.WithSerializer(MySerializer{}))

You will be capable to define a msgpack, yaml serializers if you want.

Custom logger

By default the internal logger is disabled, you can provide a more verbose logger with options:

import (
	"context"
	"fmt"
	"log"

	"github.com/thoas/bokchoy/logging"
)

func main() {
	logger, err := logging.NewDevelopmentLogger()
	if err != nil {
		log.Fatal(err)
	}

	defer logger.Sync()

    bokchoy.New(ctx, bokchoy.Config{
        Broker: bokchoy.BrokerConfig{
            Type: "redis",
            Redis: bokchoy.RedisConfig{
                Type: "client",
                Client: bokchoy.RedisClientConfig{
                    Addr: "localhost:6379",
                },
            },
        },
    }, bokchoy.WithLogger(logger))
}

The builtin logger is based on zap but you can provide your own implementation easily if you have a central component.

If you don't need that much information, you can enable the Logger middleware.

Worker Concurrency

By default the worker concurrency is set to 1, you can override it based on your server capability, Bokchoy will spawn multiple goroutines to handle your tasks.

engine.Queue("tasks.message").HandleFunc(func(r *bokchoy.Request) error {
    fmt.Println("Receive request", r)
    fmt.Println("Payload:", r.Task.Payload)

    return nil
}, bokchoy.WithConcurrency(5))

You can still set it globally with bokchoy.WithConcurrency option when initializing the engine.

Retries

If your task handler is returning an error, the task will be marked as failed and retried 3 times, based on intervals: 60 seconds, 120 seconds, 180 seconds.

You can customize this globally on the engine or when publishing a new task by using bokchoy.WithMaxRetries and bokchoy.WithRetryIntervals options.

bokchoy.WithMaxRetries(1)
bokchoy.WithRetryIntervals([]time.Duration{
	180 * time.Second,
})

Timeout

By default a task will be forced to timeout and marked as canceled if its running time exceed 180 seconds.

You can customize this globally or when publishing a new task by using bokchoy.WithTimeout option:

bokchoy.WithTimeout(5*time.Second)

The worker will regain control and process the next task but be careful, each task is running in a goroutine so you have to cancel your task at some point or it will be leaking.

Catch events

You can catch events by registering handlers on your queue when your tasks are starting, succeeding, completing or failing.

queue := engine.Queue("tasks.message")
queue.OnStartFunc(func(r *bokchoy.Request) error {
    // we update the context by adding a value
    *r = *r.WithContext(context.WithValue(r.Context(), "foo", "bar"))

    return nil
})

queue.OnCompleteFunc(func(r *bokchoy.Request) error {
    fmt.Println(r.Context().Value("foo"))

    return nil
})

queue.OnSuccessFunc(func(r *bokchoy.Request) error {
    fmt.Println(r.Context().Value("foo"))

    return nil
})

queue.OnFailureFunc(func(r *bokchoy.Request) error {
    fmt.Println(r.Context().Value("foo"))

    return nil
})

Store results

By default, if you don't mutate the task in the handler its result will be always nil.

You can store a result in your task to keep it for later, for example: you might need statistics from a twitter profile to save them later.

queue.HandleFunc(func(r *bokchoy.Request) error {
	r.Task.Result = map[string]string{"result": "wow!"}

	return nil
})

You can store anything as long as your serializer can serializes it.

Keep in mind the default task TTL is 180 seconds, you can override it with bokchoy.WithTTL option.

Helpers

Let's define our previous queue:

queue := engine.Queue("tasks.message")

Empty the queue

queue.Empty()

It will remove all waiting tasks from your queue.

Cancel a waiting task

We produce a task without running the worker:

payload := map[string]string{
    "data": "hello world",
}

task, err := queue.Publish(ctx, payload)
if err != nil {
    log.Fatal(err)
}

Then we can cancel it by using its ID:

queue.Cancel(ctx, task.ID)

Retrieve a published task from the queue

queue.Get(ctx, task.ID)

Retrieve statistics from a queue

stats, err := queue.Count(ctx)
if err != nil {
    log.Fatal(err)
}

fmt.Println("Number of waiting tasks:", stats.Direct)
fmt.Println("Number of delayed tasks:", stats.Delayed)
fmt.Println("Number of total tasks:", stats.Total)

Middleware handlers

Bokchoy comes equipped with an optional middleware package, providing a suite of standard middlewares. Middlewares have the same API as handlers. It's easy to implement them and think of them like net/http middlewares, they share the same purpose to follow the lifecycle of a Bokchoy request.

Core middlewares

---

bokchoy/middleware	description
Logger	Logs the start and end of each request with the elapsed processing time
Recoverer	Gracefully absorb panics and prints the stack trace
RequestID	Injects a request ID into the context of each request
Timeout	Signals to the request context when the timeout deadline is reached

---

See middleware directory for more information.

FAQs

Are Task IDs unique?

Yes! There are based on ulid.

Is exactly-once execution of tasks guaranteed?

It's guaranteed by the underlying broker, it uses BRPOP/BLPOP from Redis.

If multiple clients are blocked for the same key, the first client to be served is the one that was waiting for more time (the first that blocked for the key).

Contributing

• Ping me on twitter:
  • @thoas
• Fork the project
• Fix bugs

Don't hesitate ;)

Project history

Bokchoy is highly influenced by the great rq and celery.

Both are great projects well maintained but only used in a Python ecosystem.

Some parts (middlewares mostly) of Bokchoy are heavily inspired or taken from go-chi.