Key concepts in Acquia Cloud

Acquia Cloud is a cloud-based hosting platform tuned for Drupal performance and scalability. Acquia manages your servers and provides an easy-to-use workflow for developing, staging, and publishing your Drupal applications. We designed the Acquia Cloud workflow to support the best practices identified by the Drupal community for managing a Drupal application. In order to make the most of Acquia Cloud, you should understand the following key concepts.

Comparing Acquia Cloud to virtual private servers

Acquia Cloud is not just a virtual private server. It is a carefully crafted platform optimized to run highly available Drupal applications. In creating Acquia Cloud, we have carefully selected, configured, tested, and deployed the best open-source platform for this goal.

Your Acquia Cloud platform may consist of a single shared server or one or more dedicated servers. Each Acquia Cloud server runs the same versions of each element of the platform:

  • Linux operating system
  • Apache web server
  • MySQL database
  • nginx reverse proxy load balancing server
  • Varnish Cache

This enables Acquia to efficiently provision, test, manage, monitor, and upgrade the platform. As a result, you cannot select and install your own versions of the operating system, web server, or other platform software your application runs on. For more information about what is installed on Acquia Cloud and what other software is and is not supported, see Acquia Cloud technology platform and supported software.

You have non-privileged access to your servers using SSH, using a public key you register with your Acquia Cloud account. You do not have root or sudo privileges. You have full control over the Drupal docroot, including Drupal core, contributed, and custom modules and the web servers' .htaccess files, but do not have write privileges for php.ini, my.cnf, or Apache configuration files.

Code, databases, and files

The key components of a Drupal application are the code, databases, and files.

  • The code is your Drupal core installation, any contributed or custom Drupal modules you have installed, and themes.
  • The databases store your application’s content, configuration, and other information, including Drupal nodes, user information and log information.
  • The files store user-uploaded objects, such as pictures and PDF files.

The Acquia Cloud workflow enables you to manage your application’s code, database, and files separately in each of the local, Development, Staging, and Production environments. For more information, read:

Multiple environments: local, Development, Staging, and Production

Each Acquia Cloud application has four (or more) environments to optimize your application development and publishing workflow:

  • Local - You develop your application locally. This enables you to see the effects of your changes immediately. Using version control enables multiple web developers to work simultaneously on different parts of the application.
  • Development - When you have multiple developers working on an application, the Development environment is for initial integration testing. The developers commit their changes to the version control system, and the changes are deployed immediately in the Development environment so that everyone can see them. Alternatively, you can enable the Live Development feature, and edit your code directly in your Development or Staging environment.
  • Staging - In the Staging environment, you can test changes to your application before deploying them to Production.
  • Production - Your users see only your Production environment. You can pull your application’s database and files from Production to Staging or Development, so you can work with the current state and content of your application as you test and develop it.

Acquia Cloud provides a separate instance of your databases and file directories for each of your application's environments.
The Acquia Cloud settings include file for your application configures your settings.php file so that for each environment, your application connects to the correct database instance and files directory.

If you are an Acquia Cloud Enterprise customer, you can, if you choose, set up additional environments. This can be useful for integration or load testing and may also enable Acquia Cloud to fit better with your development workflow.

Developing code locally or in the Development environment

Acquia Cloud supports two models for developing code: local development and live development.

  • Using local development, you develop your application locally, using a local checkout of your Acquia Cloud repository, and then commit to your codebase. Acquia Dev Desktop is a free tool you can use to accelerate your local development and sync with your Acquia Cloud environments.
  • Using live development, you develop your application on your Acquia Cloud Development environment.

Version control and multiple environments

Acquia Cloud enforces the use of a version control system to efficiently manage your codebase. We support the Git or version control system. As you develop your application locally, you send changes to your application’s code on Acquia Cloud using version control software, instead of copying the files directly using file upload tools, such as FTP. If you are not familiar with using version control and multiple environments, we believe that the time you spend learning these best practices will pay off with more efficient, more flexible, and less error-prone development and deployment.

Any environment can deploy any branch or tag from your code repository. An environment that is deploying a branch automatically gets any code committed to that branch. So, when you commit your code to your codebase (for example, in master, if you are using Git, your changes are automatically deployed.

Debugging your application

If your application is on Acquia Cloud Professional, you are responsible for managing your application, while Acquia manages your servers. To successfully manage your application, you should be able to perform the following basic debugging tasks:

  • Looking at the Apache error logs to review PHP errors
  • Running basic Drush commands from the command line, such as drush status, to obtain error messages for debugging applications that may be offline

Load balancing

Acquia Cloud uses nginx for HTTP and HTTPS load balancing. When the load balancer detects a web server failure, it will stop sending web requests to the failed server. To guard against load balancer failures, Acquia uses a redundant load balancer configuration, with an active load balancer backed up by a passive load balancer. If the active load balancer fails, the passive load balancer is available to take over.

Acquia's operational infrastructure constantly monitors all load balancers (and the websites behind those balancers) to ensure that they are accessible, reliable, and reachable. When our monitoring detects an error, it immediately alerts our 24x7 operations staff. We then determine the reason for the failure, which can include high website traffic, a denial-of-service attack, or hardware failure. Depending on the type of failure, the passive balancer is brought online within seconds.

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