Pacemaker Import Community is designed to operate in single and multithreaded/multiprocess environments and requires sharing of data even between components in a single process and between threads and processes.

  • The registry takes effect whenever data needs to be shared

The default registry implementation works only in a single-threaded environment, where it must not handle multiple issues simultaneously that might occur in multithreaded or multiprocess environments.

Multithreading and multiprocessing considerations

In most use cases, a single process is enough and already given with the core components of a registry implementation.

Depending on the environment in which Pacemaker Import Community gets used e.g., Pacemaker Enterprise, you may need a registry processor implementation that meets the requirements of that environment.


Version of a method for a multiprocessing environment:

namespace TechDivision\Import\Services;

class RegistryProcessor implements RegistryProcessorInterface

    // other methods still go here

     * This method merges the passed attributes with an array that
     * has already been added under the given key.
     * If no value will be found under the passed key, the attributes
     * will be registered.
     * @param mixed $key        The key of the attributes that have to be merged with the passed ones
     * @param array $attributes The attributes that have to be merged with the existing ones
     * @return void
     * @throws \Exception Is thrown, if the already registered value is no array
     * @link
    public function mergeAttributesRecursive($key, array $attributes) (1)

        // merge the passed attributes in a safe manner
        return function ($k, $a) use ($key, $attributes) {
            // do the merge here assuming we've to handle multiple processes

        // throw an exception if the key exists, but the found value is not of type array
        throw new \Exception(sprintf('Can\'t merge attributes, because value for key %s already exists, but is not of type array', $key));
1 As for Pacemaker Enterprise, e.g., with the use of consumer we provide the method mergeAttributesRecursive()