Using BLT with Config Split outside Acquia Cloud or Pantheon Hosting

I am currently building a Drupal 8 application which is running outside Acquia Cloud, and I noticed there are a few 'magic' settings I'm used to working on Acquia Cloud which don't work if you aren't inside an Acquia or Pantheon environment; most notably, the automatic Configuration Split settings choice (for environments like local, dev, and prod) don't work if you're in a custom hosting environment.

You have to basically reset the settings BLT provides, and tell Drupal which config split should be active based on your own logic. In my case, I have a site which only has a local, ci, and prod environment. To override the settings defined in BLT's included config.settings.php file, I created a config.settings.php file in my site in the path docroot/sites/settings/config.settings.php, and I put in the following contents:

* Settings overrides for configuration management.

// Disable all splits which may have been enabled by BLT's configuration.
foreach ($split_envs as $split_env) {
  $config["$split_filename_prefix.$split_env"]['status'] = FALSE;

$split = 'none';

// Local env.
if ($is_local_env) {
  $split = 'local';
// CI env.
if ($is_ci_env) {
  $split = 'ci';
// Prod env.
if (getenv('K8S_ENVIRONMENT') == 'prod') {
  $split = 'prod';

// Enable the environment split only if it exists.
if ($split != 'none') {
  $config["$split_filename_prefix.$split"]['status'] = TRUE;

The K8S_ENVIRONMENT refers to an environment variable I have set up in the production Kubernetes cluster where the BLT Drupal 8 codebase is running. There are a few other little tweaks I've made to make this BLT project build and run inside a Kubernetes cluster, but I'll leave those for another blog post and another day :)


The article code works great with BLT 11 and lower.

In BLT 12, $split_env has the env name as the array key rather than the value. E.g. ("'local' => true", rather than "0 => 'local'"). This means the local split doesn't get disabled with the given code above.

It's possible to support both versions with something like this:

// Disable all splits which may have been enabled by BLT's configuration.
if (isset($split_envs)) {
  if (version_compare(\Acquia\Blt\Robo\Blt::VERSION,"12.0.0","<")) {
    foreach ($split_envs as $split_env_key => $split_env_val) {
      $config["config_split.config_split.$split_env_val"]['status'] = FALSE;
  else {
    foreach ($split_envs as $split_env_key => $split_env_val) {
      $config["config_split.config_split.$split_env_key"]['status'] = FALSE;

And where would you have to put this in order to get \Acquia\Blt\Robo\Blt? You have to be able to load that class, and that'd be done at the vendor level and I'm not touching that.