DruidServerDiscovery.java

/**
 * This interface is only used internally for discovering Druid servers in the cluster, its implementation should not
 * involve any external announcement or discovery, and should never change the state of a Druid cluster.
 */
public interface DruidServerDiscovery
{

  /**
   * Find all the Druid servers that have the specified type
   *
   * @param type the type of Druid servers we want to find
   * @return a list of server metadata from matched Druid servers
   * @throws Exception
   */
  List<DruidServerMetadata> getServersForType(String type) throws Exception;

  /**
   * Find the Druid server that is the leader of the specified type
   *
   * @param type the type of the leader
   * @return the leader's server metadata
   * @throws Exception
   */
  DruidServerMetadata getLeaderForType(String type) throws Exception;

  /**
   * Find all the Druid servers that have the specified type and service name
   *
   * @param type the type of Druid servers we want to find
   * @param service the service name of Druid servers we want to find. It is specified in druid.service runtime properties
   * @return a list of server metadata from matched Druid servers
   * @throws Exception
   */
  List<DruidServerMetadata> getServersForTypeWithService(String type, String service) throws Exception;
}