Serverless Laravel

Last week I introduced Bref as a solution to running PHP serverless.

Today let's try to deploy a Laravel application on AWS lambda using Bref. The code shown in this article is available on GitHub.

You can check out the demo Laravel application on AWS lambda here: https://k6ay4xiyld.execute-api.eu-west-3.amazonaws.com/dev. It is a simple application that uses a 3rd party HTTP API to convert between currencies.

An introduction to serverless PHP

Serverless basically means "Running apps without worrying about servers". The main difference with a traditional hosting is that you do not maintain the servers and reserve their capacity. They are scaled up or down automatically and you pay only for what you use.

One notable example is AWS S3: instead of renting a fix disk space, you pay for only the storage you are actually using. AWS S3 has no limits, you can store 10kb or 10Tb and you do not need to scale up or down the storage. AWS S3 is serverless file storage.

The idea behind serverless applications, aka Function as a Service (FaaS) is to apply the same principles:

Serverless hosting has the advantages of scaling very well since there are (theoretically) no limits. It can also help optimize costs by avoiding paying for unused server resources. You can read more about advantages and drawbacks here.

Making PHP work on AWS Lambda

I will take the example of AWS Lambda because it is the most popular provider for serverless applications, but there are other providers available. Unfortunately AWS Lambda does not support PHP (supported languages are for example Javascript, Go, Python…). To run PHP we must add the PHP binary in the lambda and have, for example, Javascript execute it.

The technical details can be found in this section so I will not cover them again. The conclusion is that deploying PHP on serverless providers is possible but a PITA. That is how Bref is born.

Bref's goals are:

For the first part Bref builds on top of the serverless framework and brings additional tooling specific to PHP.

For the second part I have been working on bridges to make PHP frameworks work on lambdas.

Laravel on lambdas

What follows is a step-by-step explanation, if you want the short version either check out the Bref documentation or the demo on GitHub. I will also focus on AWS Lambda here because it is what I used for those tests.

Let's start by creating a new Laravel application:

$ composer create-project laravel/laravel demo
$ cd demo

Now let's install Bref (read the setup instructions) and initialize it:

$ composer require mnapoli/bref
$ vendor/bin/bref init

When applications run on lambdas they do not work like with traditional hosting providers: public/index.php is no longer the application's entry point because there is no Apache, Nginx or PHP-FPM. Bref takes care of connecting the HTTP layer (API Gateway + AWS lambda integration) to your application. It will convert the HTTP request from API Gateway into a format Laravel can understand, and will convert back the HTTP response the other way around.

Note: you don't need to know about API Gateway, Bref takes care of that part.

All we need to do is write a bref.php file: that will be the entrypoint of the application. Let's write that file at the root of the project:

<?php

define('LARAVEL_START', microtime(true));

require __DIR__.'/vendor/autoload.php';

$app = require_once __DIR__.'/bootstrap/app.php';

$kernel = $app->make(Illuminate\Contracts\Http\Kernel::class);

$app = new \Bref\Application;
$app->httpHandler(new Bref\Bridge\Laravel\LaravelAdapter($kernel));
$app->run();

As you can see it's very similar to public/index.php except that Laravel will not run itself, instead Bref will run Laravel.

That is done using the $app->httpHandler(...) line (documentation). You can use any PSR-17 framework as a HTTP handler, here we are configuring the Laravel HTTP Kernel using an adapter. The adapter is necessary because Laravel is not compliant with PSR-17 yet.

The next step is to configure which directories to deploy on the lambda. That can be configured in the serverless.yml file that was created in your project:

package:
  exclude:
    # ...
  include:
    # ...
    # Add the following directories:
    - 'app/**'
    - 'bootstrap/**'
    - 'config/**'
    - 'resources/**'
    - 'routes/**'
    - 'vendor/**'

Now all we would have to do in theory would be to deploy using:

$ vendor/bin/bref deploy

But with Laravel we have a few extra steps to take.

File storage

The filesystem on lambdas is read-only, except for the /tmp folder. That means that Laravel's storage directory will not work out of the box if we keep it inside our project.

We need to tell Laravel to use the /tmp/storage folder instead. Add this line in bootstrap/app.php after $app = new Illuminate\Foundation\Application:

/*
 * Allow overriding the storage path in production using an environment variable.
 */
$app->useStoragePath(env('APP_STORAGE', $app->storagePath()));

By using an environment variable we can keep the classic behavior when running the application locally (or on a traditional server) and we can set this variable to /tmp/storage on AWS lambda.

To set environment variables on AWS lambda we can use serverless.yml:

functions:
  main:
    ...
    environment:
      APP_STORAGE: '/tmp/storage'

Now since this directory doesn't exist by default on AWS lambda we need to create it on the fly. Add these lines to bref.php:

// ...

$app = require_once __DIR__.'/bootstrap/app.php';

// Laravel does not create that directory automatically so we have to create it
if (!is_dir(storage_path('framework/views'))) {
    if (!mkdir(storage_path('framework/views'), 0755, true)) {
        die('Cannot create directory ' . storage_path('framework/views'));
    }
}

// ...

Configuration

There are other parameters we will want to override for the production environment. What we will do is create a .env.production file in our project and configure our variables here:

APP_ENV=production
APP_DEBUG=false
# ...

To make Laravel use this configuration in production we will write a build hook. Build hooks are scripts that are executed before Bref deploys your application. Let's write those in a .bref.yml file:

hooks:
    build:
        # Rename the `.env.production` file to `.env`
        - 'rm .env && cp .env.production .env'

Note: those commands are run in a separate directory than your project, your own .env file will not be deleted.

By default Bref installs Composer dependencies and optimizes the autoloader, we do not need to do it ourselves.

In order to optimize the application we want to cache the configuration. Let's add other hooks to the list:

hooks:
    build:
        # Use the `.env.production` file as `.env`
        - 'rm .env && cp .env.production .env'
        - 'rm bootstrap/cache/*.php'
        - 'php artisan config:cache'

The php artisan config:cache dumps the optimized configuration files. The problem with that is that it will also dump all file paths as absolute paths (e.g. storage directory, views, etc.). Since Laravel is in a different directory on our computer than on AWS lambda the dumped configuration will not work in production.

We need to tell Laravel to generate relative paths. Let's do that by customizing the root path of Laravel in bootstrap/app.php as shown below. The APP_DIR variable will allow us to replace the absolute path by . (relative path) when generating the lambda.

$app = new Illuminate\Foundation\Application(
    env('APP_DIR', realpath(__DIR__.'/../'))
);

Note: we do not want to hardcode . directly here because that would mess up Laravel's behavior in other cases (for example with artisan serve or when running Laravel with Apache/Nginx).

Let's add that new environment variable to serverless.yml:

functions:
  main:
    ...
    # Laravel configuration using environment variables:
    environment:
      APP_STORAGE: '/tmp/storage'
      APP_DIR: '.'

Let's also add that variable into our .env.production file:

# ...

# This allows to generate relative file paths for the lambda
APP_DIR=.
APP_STORAGE=/tmp/storage

Everything is good except one last problem: view cache files. Laravel runs realpath() on the path containing the cached views, and we are generating a configuration with /tmp/storage on our machine -> that directory doesn't exist on our machine, and realpath() fails. That breaks Laravel's views.

We need to remove the realpath() call in config/views.php:

-    'compiled' => realpath(storage_path('framework/views')),
+    'compiled' => storage_path('framework/views'),

All is good now!

Logging

We configured Laravel to use the /tmp/storage directory, but /tmp is ephemeral: everything in there will be lost at some point. This is not a good place to store logs.

We need to change the logging driver and instead use the stderr driver: logs will be captured by Bref and sent directly to AWS Cloudwatch. That can be configured in .env.production:

# ...

LOG_CHANNEL=stderr

You can of course use any other driver you want (as long as it's not the file driver).

Sessions

Just like logging, storing sessions in /tmp/storage is not a good idea. If you are writing an API or any application that do not need sessions you can use the array driver:

# ...

SESSION_DRIVER=array

If you need sessions you can store them in database, Redis, etc.

Routing

Finally when deploying a lambda AWS creates a random URL that contains a /dev suffix. Because of that the default route (/) will not work out of the box. We can change the route for the welcome page:

// routes/web.php

Route::get('/dev', function () {
    return view('welcome');
});

If you use a custom domain however the suffix will disappear so it is only an issue when doing small tests like this.

Deploying

We are finally done for a functional serverless Laravel. Let's deploy:

$ vendor/bin/bref deploy

Our app should now be online, get the URL of the app by running vendor/bin/bref info.

Going further

There are still many things to improve with Bref and Laravel:

I am planning to work on those topics in the months to come, and help is always welcome.

Conclusion

If you want to learn more about Bref and Laravel:

To learn more about serverless in general:

If you want to get started I can also accompany you, drop me a line at matthieu at mnapoli dot fr.

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