The upgrade from Drupal 8 to Drupal 9 should be relatively uncomplicated in theory. Drupal 9 will predominately deprecate certain functions from Drupal 8 to create a modern codebase. The subsequently answered questions might help your development team while planning an upgrade to Drupal 9.
Does upgrading from Drupal 8 to 9 require platform changes, and does this affect software middleware versions?
Drupal 9 will run with PHP 7.3 or PHP 7.4 which is currently available on the platform. In the Cloud UI, your team can switch to the appropriate PHP version in all environments from Development to Production, allowing you to test your application on your subscription.
Drupal 9 uses MySQL 5.7 uses as a minimum. Acquia Cloud subscribers will not have access, until a later date, to this version. If you receive an error message related to database versions while updating or installing Drupal 9, you must install and configure the MySQL 5.6 driver module. The module is developed and maintained by Acquia to resolve the error until our platform is able to provide MySQL 5.7.
Will the upgrade require data migration?
Your development team may have to plan for data migration, and it will depend on custom modules and configuration. Each customer needs to assess that intended objective at an organisational level. If your custom codebase requires a complex data migration, Acquia Professional Services could be engaged to assist with the upgrade. Please reach out to your Account Manager or our Sales Team to discuss an Acquia Professional Services engagement for assistance.
Does Acquia intend to provide Long Term Support (LTS) for Drupal 8 after November 2021?
The Long Term Support (LTS) for Drupal ends in November, 2021 as discussed in the Drupal 8 Long-Term Support page.
For Acquia's Long Term Support (LTS) documentation with an in-depth discussion, please review our article, Supported software life cycle.
Something to consider between Drupal 8 and Drupal 9, is if your codebase has a lot of custom code relying on deprecated D8 functions, this needs organisation awareness and careful focus. The Drupal API functions called in your custom code will need to be upgraded and will require some effort for your development team to modernise. However, that refactoring will not be as extensive as when your development team upgraded Drupal 7 custom code to Drupal 8. If you need assistance in reviewing your application or performing a migration of your site, please reach out to your Account Manager or our Sales Team to discuss an Acquia Professional Services engagement.
When should my team start the upgrade process?
The upgrade process depends on the complexity of your application's configuration, and also the use of contributed and custom modules. As every website and the complexity of that website is different, you will need to evaluate, plan, and test your application. If you need assistance with the evaluation or would like to contract for the migration work, please reach out to your Account Manager or our Sales Team to discuss an Acquia Professional Services engagement for assistance.
Below are some links that can help your organisation tools and further information to help you in your upgrade from Drupal 8 to Drupal 9.