These are separate questions...

The Cloud™: noun

Someone else's hard drive

Cloud computing: noun

Abstracting away physical infrastructure

Disposable application design

What makes an application cloud-friendly?

They're not rules

They're more like guidelines

Split code from content

Your application is disposable. Your data is not.

Data flow

You don't get an in-between option

Take-away

Cleanly separate "Dev provided" and "user provided" files

What is configuration?

Does config come from the developer or the user?

Git or Database?

Drupal Config Management

1. Configure in UI / DB
2. Export to YAML
3. Commit to Git
4. Push / Pull
5. Import back to DB

Take-away

Decide

What happens at runtime
stays at runtime

Dependency inject your environment

• DB credentials (Solr, Redis, etc.)
• API keys
• All paths on disk
• Domain names

Environment variables

getenv('foo');

$_ENV['foo'];

$_ENV['foo']['bar'];
        

Need glue code

Platform.sh / SensioCloud

Symfony 3

// platform_parameters.php
// Configure the database.
if (isset($_ENV['PLATFORM_RELATIONSHIPS'])) {
    $dbRelationshipName = 'database';
    $relationships = json_decode(base64_decode($_ENV['PLATFORM_RELATIONSHIPS']), true);

    foreach ($relationships[$dbRelationshipName] as $endpoint) {
        if (!empty($endpoint['query']['is_master'])) {
            $container->setParameter('database_driver', 'pdo_'.$endpoint['scheme']);
            $container->setParameter('database_host', $endpoint['host']);
            $container->setParameter('database_port', $endpoint['port']);
            $container->setParameter('database_name', $endpoint['path']);
            $container->setParameter('database_user', $endpoint['username']);
            $container->setParameter('database_password', $endpoint['password']);
            $container->setParameter('database_path', '');
            break;
        }
    }
}
// Set a default unique secret, based on a project-specific entropy value.
if (isset($_ENV['PLATFORM_PROJECT_ENTROPY'])) {
    $container->setParameter('kernel.secret', $_ENV['PLATFORM_PROJECT_ENTROPY']);
}
        

Platform.sh / Symfony 4

// Set the DATABASE_URL for Doctrine, if necessary.
if (!isset($_ENV['DATABASE_URL'])) {
    if (isset($_ENV['PLATFORM_RELATIONSHIPS'])) {
        $dbRelationshipName = 'database';
        $relationships = json_decode(base64_decode($_ENV['PLATFORM_RELATIONSHIPS']),true);
        foreach ($relationships[$dbRelationshipName] as $endpoint) {
            if (!empty($endpoint['query']['is_master'])) {
                $dbUrl = sprintf("%s://%s:%s@%s:%s/%s?charset=utf8mb4&serverVersion=10.2",
                  $endpoint['scheme'], $endpoint['username'], $endpoint['password'],
                  $endpoint['host'], $endpoint['port'],
                  $endpoint['path']);
                break;
            }
            $_ENV['DATABASE_URL'] = $dbUrl;
        }
    }
    else {
        // Hack the Doctrine URL to be syntactically valid in a build hook, even
        // though it shouldn't be used.
        $dbUrl = sprintf("%s://%s:%s@%s:%s/%s?charset=utf8mb4&serverVersion=10.2",
          'mysql', '', '', 'localhost', 3306, '');
        $_ENV['DATABASE_URL'] = $dbUrl;
    }
}

// Set the application secret if it's not already set.
if (!isset($_ENV['APP_SECRET']) && isset($_ENV['PLATFORM_PROJECT_ENTROPY'])) {
    $_ENV['APP_SECRET'] = $_ENV['PLATFORM_PROJECT_ENTROPY'];
}
        

In the container

parameters:
    app.connection.port: '%env(int:DATABASE_PORT)%'
        

parameters:
    project_dir: '/foo/bar'
    env(DB): 'sqlite://%%project_dir%%/var/data.db'
    db_dsn: '%env(resolve:DB)%'
        

parameters:
    env(SOME_VALUE): 'NWE3OWExYzg2NmVmZWY5Y2ExODAwZjk3MWQ2ODlmM2U='
    app.some_value: '%env(base64:SOME_VALUE)%'

    env(NUM_ITEMS): 'App\\Entity\\BlogPost::NUM_ITEMS'
    app.num_items: '%env(constant:NUM_ITEMS)%'
        

• Request::setTrustedHosts()

Constants?

Take-away

Dependency inject your environment

User-configured connections

Installers

1. Ask for DB credentials
2. Ask user for basic site info
3. Write credentials to config file
4. Populate DB
5. Write basic site info to config file/DB
6. Profit!!!

Cloud

Better installers

• Pre-include connection glue
• Installer skips pre-populated values
• Do not download from installer

Avoid lock-in

Always be able to
take your business elsewhere.

Use Free Software

Use replaceable services

Google has killed...

• Reader
• iGoogle
• Google Talk
• Google Health
• Knol
• Google Insights
• Picnik
• Buzz
• Aardvark
• Sidewiki
• Notebook
• Dictionary
• Labs
• Wave
• SearchWiki
• Dodgeball
• Jaiku
• Lively
• Page Creator
• Zeitgeist
• Answers
• Google X
• Catalog
• Web Accelerator
• Video Player
• Sets
• SearchMash
• Writely

Source: WordStream (2015)

To summarize...

Remember what they say when you assume