Drupal module to support idempotent migrations (manifests)
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LICENSE.md
README.md
kw_manifests.api.php
kw_manifests.drush.inc
kw_manifests.info
kw_manifests.module

README.md

Kraftwagen Manifests

Kraftwagen Manifests is a Drupal module that provides the means to register and execute idempotent migrations. Usually migrations are intented to be only ran once (Drupal already provides this with hook_update_N), but in quite a lot of cases this isn't very usefull.

Usage

An idempotent migration is called a manifest in Kraftwagen Manifests. You can register a manifest by implementing hook_kw_manifests_info in your module's .install file.

/**
 * Implements hook_kw_manifests_info().
 */
function mymodule_kw_manifests_info() {
  $manifests = array();

  $manifests['my_manifest'] = array(
    'callback' => 'mymodule_manifest_my_manifest',
  );

  return $manifests;
}

function mymodule_manifest_my_manifest() {
  // some very trivial example
  variable_set('some_variable', 'desired value');
}

Take a look at kw_manifests.api.php for more information about registering manifests. The registration makes it for example possible to mark other manifests as a dependency, to make sure another manifest is executed before yours.

You can execute all the manifests that are registered in enabled modules by running the following command (requires Drush to be installed).

drush kw-manifests

Things to note

  • It is hard, if not impossible to reliably determine which manifest will be ran first. The only promise Kraftwagen Manifests makes, is that the specified dependencies of your manifest will be executed before yours. Do not rely on the execution order of manifests that are not marked as dependency.
  • Especially when your module contains a lot of manifests, they can become a little hard to manage. Use the 'file' key in the hook_kw_manifests_info implementation to keep your manifests in a seperate file, or maybe even a few seperate files to keep your .install file clean. Make smart use of the 'callback arguments' key to prevent a lot of repetition in your manifests.