On Wednesday, 4 October 2017, Drupal 8.4 was released. Drupal 8.4 requires Drush 8.1.12 or higher. Drush 9 introduces significant changes in the way that Drupal works with Drush and Composer. While customers can upgrade to Drupal 8.4 and Drush 9 once they are released, the following should be noted:
While Drush 9 will be available upon release, the Acquia Cloud platform will continue to default to Drush 8.1.12. Any customer who wants to upgrade to Drupal 8.4 will need to specifically call Drush 9 to invoke Drush 9. Moving forward, Drush 9 must be installed locally as Drush 9 no longer includes a global install command.
For customers using Remote Administration (RA) services, all Drupal applications 8.4+ must be built using a composer.json. Code updates using Drush will no longer be available as the `pm-update*` functionality is now deprecated in Drush. However, database updates will still require Drush. As a consequence, Drush must be installed at the application level using Composer. Read about how to move your D8 site to a composer build.
Acquia is actively exploring tooling to ensure that Composer can be used to detect Drupal-specific security updates. Until a solution is developed, all security updates to applications running 8.4+ will need to be detected and applied manually for those clients with RA Premium. It is likely that RA services will depend on the requirement of specific Composer projects. RA clients will be informed of changes to requirements as soon as a solution is implemented.
BLT 8.9.6+ is compatible with Drupal 8.4. BLT 8.9.6+ will permit you to install Drupal 8.4 and all of its dependencies (e.g., Drush 9, Lightning 2.2+, Symfony 3, etc.) and BLT's own code will continue to execute correctly.
However, upgrading from Drupal 8.3 to 8.4 requires a number of manual update steps to make your application and custom theme compatible with the new version of core. See our documentation for additional guidance regarding changes required to make Acquia BLT compatible with Drupal 8.4.
Acquia Content Hub
At this time, the Acquia Content Hub module is now compatible with Drupal 8.4.
There may be additional issues identified as impacted by these changes. When those items are identified, we will update this article with details and a potential workaround. We will continue to update this document as these issues are identified and will provide instructions for remediation, where applicable. If you have questions, please feel free to utilize our Support team by filing a ticket at https://cloud.acquia.com/support or visiting the Acquia Help Center.