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A project scaffold implementing the Lucid architecture in Laravel 5
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Lucid

The Lucid Architecture is a software architecture that consolidates code-base maintenance as the application scales, from becoming overwhelming to handle, gets us rid of rotting code that will later become legacy code, and translate the day-to-day language such as Feature and Service into actual, physical code.

Read more about the Lucid Architecture Concept.

If you prefer a video, watch the announcement of The Lucid Architecture at LaraconEU 2016:

The Lucid Architecture for Building Scalable Applications - Laracon EU 2016

Abed Halawi - The Lucid Architecture for Building Scalable Applications

Join The Community on Slack

Slack Status

Index

Installation

5.8

To start your project with Lucid right away, run the following command:

composer create-project lucid-arch/laravel my-project

This will give you a Laravel 5.8 installation with Lucid out-of-the-box. If you wish to download other versions of Laravel you may specify it as well:

5.7
composer create-project lucid-arch/laravel=5.7.x my-project-5.7

Literally 5.7.x and not 5.7.0 or 5.7.1...

5.6
composer create-project lucid-arch/laravel=5.6.x my-project-5.6

Literally 5.6.x and not 5.6.0 or 5.6.1...

5.5
composer create-project lucid-arch/laravel=5.5.x my-project-5.5
5.4
composer create-project lucid-arch/laravel=5.4.x my-project-5.4
5.3
composer create-project lucid-arch/laravel=5.3.x my-project-5.3

Introduction

Directory Structure

src
├── Data
├── Domains
    └── * domain name *
            ├── Jobs
├── Foundation
└── Services
    └── * service name *
        ├── Console
        ├── Features
        ├── Http
        ├── Providers
        ├── Tests
        ├── database
        └── resources

Components

Component Path Description
Service src/Service/[service] Place for the Services
Feature src/Services/[service]/Features/[feature] Place for the Features of Services
Job src/Domains/[domain]/Jobs/[job] Place for the Jobs that expose the functionalities of Domains
Data src/Data Place for models, repositories, value objects and anything data-related
Foundation src/Foundation Place for foundational (abstract) elements used across the application

Service

Each part of an application is a service (i.e. Api, Web, Backend). Typically, each of these will have their way of handling and responding to requests, implementing different features of our application, hence, each of them will have their own routes, controllers, features and operations. A Service will seem like a sub-installation of a Laravel application, though it is just a logical grouping than anything else.

To better understand the concept behind Services, think of the terminology as: "Our application exposes data through an Api service", "You can manipulate and manage the data through the Backend service".

One other perk of using Lucid is that it makes the transition process to a Microservices architecture simpler, when the application requires it. See Microservices.

Service Directory Structure

Imagine we have generated a service called Api, can be done using the lucid cli by running:

You might want to Setup to be able to use the lucid command.

lucid make:service api

We will get the following directory structure:

src
└── Services
    └── Api
        ├── Console
        ├── Features
        ├── Http
        │   ├── Controllers
        │   ├── Middleware
        │   ├── Requests
        │   └── routes.php
        ├── Providers
        │   ├── ApiServiceProvider.php
        │   └── RouteServiceProvider.php
        ├── Tests
        │   └── Features
        ├── database
        │   ├── migrations
        │   └── seeds
        └── resources
            ├── lang
            └── views
                └── welcome.blade.php

Feature

A Feature is exactly what a feature is in our application (think Login feature, Search for hotel feature, etc.) as a class. Features are what the Services' controllers will serve, so our controllers will end up having only one line in our methods, hence, the thinnest controllers ever! Here's an example of generating a feature and serving it through a controller:

You might want to Setup to be able to use the lucid command.

IMPORTANT! You need at least one service to be able to host your features. In this example we are using the Api service generated previously, referred to as api in the commands.

lucid make:feature SearchUsers api

And we will have src/Services/Api/Features/SearchUsersFeature.php and its test src/Services/Api/Tests/Features/SearchUsersFeatureTest.php.

Inside the Feature class, there's a handle method which is the method that will be called when we dispatch that feature, and it supports dependency injection, which is the perfect place to define your dependencies.

Now we need a controller to serve that feature:

lucid make:controller user api

And our UserController is in src/Services/Api/Http/Controllers/UserController.php and to serve that feature, in a controller method we need to call its serve method as such:

namespace App\Services\Api\Http\Controllers;

use App\Services\Api\Features\SearchUsersFeature;

class UserController extends Controller
{
    public function index()
    {
        return $this->serve(SearchUsersFeature::class);
    }
}

Views

To access a service's view file, prepend the file's name with the service name followed by two colons ::

Example extending view file in blade:

@extends('servicename::index')

Usage with jobs is similar:

new RespondWithViewJob('servicename::user.login')

RespondWithJsonJob accepts the following parameters:

RespondWithViewJob($template, $data = [], $status = 200, array $headers = []);

Usage of template with data:

$this->run(new RespondWithViewJob('servicename::user.list', ['users' => $users]));

Or

$this->run(RespondWithViewJob::class, [
    'template' => 'servicename::user.list',
    'data' => [
        'users' => $users
    ],
]);

Job

A Job is responsible for one element of execution in the application, and play the role of a step in the accomplishment of a feature. They are the stewards of reusability in our code.

Jobs live inside Domains, which requires them to be abstract, isolated and independent from any other job be it in the same domain or another - whatever the case, no Job should dispatch another Job.

They can be ran by any Feature from any Service, and it is the only way of communication between services and domains.

Example: Our SearchUsersFeature has to perform the following steps:

  • Validate user search query
  • Log the query somewhere we can look at later
  • If results were found
    • Log the results for later reference (async)
    • Increment the number of searches on the found elements (async)
    • Return results
  • If no results were found
    • Log the query in a "high priority" log so that it can be given more attention

Each of these steps will have a job in its name, implementing only that step. They must be generated in their corresponding domains that they implement the functionality of, i.e. our ValidateUserSearchQueryJob has to do with user input, hence it should be in the User domain. While logging has nothing to do with users and might be used in several other places so it gets a domain of its own and we generate the LogSearchResultsJob in that Log domain.

To generate a Job, use the make:job <job> <domain> command:

lucid make:job SearchUsersByName user

Similar to Features, Jobs also implement the handle method that gets its dependencies resolved, but sometimes we might want to pass in input that doesn't necessarily have to do with dependencies, those are the params of the job's constructor, specified here in src/Domains/User/Jobs/SearchUsersByNameJob.php:

namespace App\Domains\User\Jobs;

use Lucid\Foundation\Job;

class SearchUsersByNameJob extends Job
{
    private $query;
    private $limit;

    public function __construct($query, $limit = 25)
    {
        $this->query = $query;
        $this->limit = $limit;
    }

    public function handle(User $user)
    {
        return $user->where('name', $this->query)->take($this->limit)->get();
    }
}

Now we need to run this and the rest of the steps we mentioned in SearchUsersFeature::handle:

public function handle(Request $request)
{
    // validate input - if not valid the validator should
    // throw an exception of InvalidArgumentException
    $this->run(new ValidateUserSearchQueryJob($request->input()));

    $results = $this->run(SearchUsersJob::class, [
        'query' => $request->input('query'),
    ]);

    if (empty($results)) {
        $this->run(LogEmptySearchResultsJob::class, [
            'date' => new DateTime(),
            'query' => $request->query(),
        ]);

        $response = $this->run(new RespondWithJsonErrorJob('No users found'));
    } else {
        // this job is queueable so it will automatically get queued
        // and dispatched later.
        $this->run(LogUserSearchJob::class, [
            'date' => new DateTime(),
            'query' => $request->input(),
            'results' => $results->lists('id'), // only the ids of the results are required
        ]);

        $response = $this->run(new RespondWithJsonJob($results));
    }

    return $response;
}

As you can see, the sequence of steps is clearly readable with the least effort possible when following each $this->run call, and the signatures of each Job are easy to understand.

A few things to note regarding the implementation above:

  • There is no difference between running a job by instantiating it like $this->run(new SomeJob) and passing its class name $this->run(SomeJob::class) it is simply a personal preference for readability and writing less code, when a Job takes only one parameter it's instantiated.
  • The order of parameters that we use when calling a job with its class name is irrelevant to their order in the Job's constructor signature. i.e.
$this->run(LogUserSearchJob::class, [
    'date' => new DateTime(),
    'query' => $request->input(),
    'resultIds' => $results->lists('id'), // only the ids of the results are required
]);
class LogUserSearchJob
{
    public function __construct($query, array $resultIds, DateTime $date)
    {
        // ...
    }
}

This will work perfectly fine, as long as the key name ('resultIds' => ...) is the same as the variable's name in the constructor ($resultIds)

  • Of course, we need to create and import (use) our Job classes with the correct namespaces, but we won't do that here since this is only to showcase and not intended to be running, for a working example see Getting Started.

Data

Data is not really a component, more like a directory for all your data-related classes such as Models, Repositories, Value Objects and anything that has to do with data (algorithms etc.).

Foundation

This is a place for foundational elements that act as the most abstract classes that do not belong in any of the components, currently holds the ServiceProvider which is the link between the services and the framework (Laravel). You might never need or use this directory for anything else, but in case you encountered a case where a class needs to be shared across all components and does belong in any, feel free to use this one.

Every service must be registered inside the foundation's service provider after being created for Laravel to know about it, simply add $this->app->register([service name]ServiceProvider::class); to the register methods of the foundation's ServiceProvider. For example, with an Api Service:

// ...
use App\Services\Api\Providers\ApiServiceProvider;
// ...
public function register()
{
    $this->app->register(ApiServiceProvider::class);
}

Getting Started

This project ships with the Lucid Console which provides an interactive user interface and a command line interface that are useful for scaffolding and exploring Services, Features, and Jobs.

Setup

The lucid executable will be in vendor/bin. If you don't have ./vendor/bin/ as part of your PATH you will need to execute it using ./vendor/bin/lucid, otherwise add it with the following command to be able to simply call lucid:

export PATH="./vendor/bin:$PATH"

For a list of all the commands that are available run lucid or see the CLI Reference.

Launching the Interactive Console (UI)

  1. Serve Application One way is to use the built-in server by running:
php artisan serve

Any other method would also work (Apache, Nginx, etc...)

  1. Run php artisan vendor:publish --provider="Lucid\Console\LucidServiceProvider"
  2. Visit your application at /lucid/dashboard

1. Create a Service

CLI
lucid make:service Api
UI

Using one of the methods above, a new service folder must've been created under src/Services with the name Api.

The Api directory will initially contain the following directories:

src/Services/Api
├── Console         # Everything that has to do with the Console (i.e. Commands)
├── Features        # Contains the Api's Features classes
├── Http            # Routes, controllers and middlewares
├── Providers       # Service providers and binding
├── database        # Database migrations and seeders
└── resources       # Assets, Lang and Views

One more step is required for Laravel to recognize the service we just created.

Register Service

  • Open src/Foundation/Providers/ServiceProvider
  • Add use App\Services\Api\Providers\ApiServiceProvider
  • In the register method add $this->app->register(ApiServiceProvider::class)

2. Create a Feature

CLI
lucid make:feature ListUsers api
UI

Using one of the methods above, the new Feature can be found at src/Services/Api/Features/ListUsersFeature.php. Now you can fill up a bunch of jobs in its handle method.

3. Create a Job

This project ships with a couple of jobs that can be found in their corresponding domains under src/Domains

CLI
lucid make:job GetUsers user
UI

Using one of the methods above, the new Job can be found at src/Domains/User/Jobs/GetUsers and now you can fill it with functionality in the handle method. For this example we will just add a static return statement:

public function handle()
{
    return [
        ['name' => 'John Doe'],
        ['name' => 'Jane Doe'],
        ['name' => 'Tommy Atkins'],
    ];
}

4. All Together

Back to the Feature we generated earlier, add $this->run(GetUsersJob) (remember to use the job with the correct namespace App\Domains\User\Jobs\GetUsersJob).

Run The Job

In ListUsersFeature::handle(Request $request)

public function handle(Request $request)
{
    $users = $this->run(GetUsersJob::class);

    return $this->run(new RespondWithJsonJob($users));
}

The RespondWithJsonJob is one of the Jobs that were shipped with this project, it lives in the Http domain and is used to respond to a request in a structured JSON format.

Serve The Feature

To be able to serve that Feature we need to create a route and a controller that does so.

Generate a plain controller with the following command

lucid make:controller user api --plain

Add the get method to it:

class UserController extends Controller
{
    public function get()
    {
        return $this->serve(ListUsersFeature::class);
    }
}

We just need to create a route that would delegate the request to our get method:

In src/Services/Api/Http/routes.php you will find the route group Route::group(['prefix' => 'api'], function() {... Add the /users route within that group.

Route::get('/users', 'UserController@get');

Now if you visit /api/users you should see the JSON structure.

Microservices

If you have been hearing about microservices lately, and wondering how that works and would like to plan your next project based on microservices, or build your application armed and ready for the shift when it occurs, Lucid is your best bet. It has been designed with scale at the core and the microservice transition in mind, it is no coincidence that the different parts of the application that will (most probably) later on become the different services with the microservice architecture are called Service. However, it is recommended that only when your monolith application grow so large that it becomes crucial to use microservices for the sake of the progression and maintenance of the project, to do the shift; because once you've built your application using Lucid, the transition to a microservice architecture will be logically simpler to plan and physically straight-forward to implement. There is a microservice counterpart to Lucid that you can check out here.

With more on the means of transitioning from a monolith to a microservice.

Event Hooks

Lucid exposes event hooks that allow you to listen on each dispatched feature, operation or job. This is especially useful for tracing:

use Illuminate\Support\Facades\Event;
use Lucid\Foundation\Events\FeatureStarted;
use Lucid\Foundation\Events\OperationStarted;
use Lucid\Foundation\Events\JobStarted;

Event::listen(FeatureStarted::class, function (FeatureStarted $event) {
    // $event->name
    // $event->arguments
});

Event::listen(OperationStarted::class, function (OperationStarted $event) {
    // $event->name
    // $event->arguments
});

Event::listen(JobStarted::class, function (JobStarted $event) {
    // $event->name
    // $event->arguments
});
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