content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.job.workflow;
  
  import alluxio.exception.ExceptionMessage;
  import alluxio.exception.JobDoesNotExistException;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.HashMap;
  import java.util.Map;
  import java.util.ServiceLoader;
  
  /**
   * Registry for {@link WorkflowExecution}.
   */
  public enum WorkflowExecutionRegistry {
    INSTANCE;
    private static final Logger LOG = LoggerFactory.getLogger(WorkflowExecutionRegistry.class);
    private final Map<Class<?>, WorkflowExecutionFactory<?>> mExecutionFactories = new HashMap<>();
  
    static {
      INSTANCE.discoverWorkflowExecutionFactories();
    }
  
    private void discoverWorkflowExecutionFactories() {
      ServiceLoader<WorkflowExecutionFactory> discoveredFactories =
          ServiceLoader.load(WorkflowExecutionFactory.class,
              WorkflowExecutionFactory.class.getClassLoader());
  
      for (WorkflowExecutionFactory executionFactory : discoveredFactories) {
        mExecutionFactories.put(executionFactory.getWorkflowConfigClass(), executionFactory);
        LOG.info("Loaded execution factory " + executionFactory.getClass().getSimpleName()
            + " for config " + executionFactory.getWorkflowConfigClass().getName());
      }
    }
  
    private WorkflowExecutionFactory getExecutionFactory(WorkflowConfig config)
        throws JobDoesNotExistException {
      if (!mExecutionFactories.containsKey(config.getClass())) {
        throw new JobDoesNotExistException(ExceptionMessage.JOB_DEFINITION_DOES_NOT_EXIST
            .getMessage(config.getName()));
      }
      return mExecutionFactories.get(config.getClass());
    }
  
    /**
     * Gets the {@link WorkflowExecution} from workflow config.
     *
     * @param config the workflow configuration
     * @return the workflow execution corresponding to the configuration
     * @throws JobDoesNotExistException when the job execution for this config does not exist
     */
    public WorkflowExecution getExecution(WorkflowConfig config) throws JobDoesNotExistException {
      return getExecutionFactory(config).create(config);
    }
  }
  