ravel/dist/db/database_provider.js

Ravel Rapid Application Development Framework

'use strict';

const ApplicationError = require('../util/application_error');

const sProviders = Symbol.for('_databaseProviders');
const sName = Symbol.for('_sName');

/**
                                     * Defines an abstract DatabaseProvider - a mechanism
                                     * by which connections can be obtained and transactions
                                     * can be entered and exited for a particular database
                                     * provider such as MySQL (see ravel-mysql-provider for an
                                     * example implementation).
                                     */let
DatabaseProvider = class DatabaseProvider {
  /**
                                            * Anything that should happen when this `DatabaseProvider` is connected to a Ravel
                                            * application via `require('provider-name')(app)` should happen here.
                                            * This includes, but is not limited to, the declaration of parameters supporting
                                            * this module via `ravelInstance.registerParameter()`. If you override this constructor,
                                            * be sure to call `super(ravelInstance, name)`.
                                            *
                                            * @param {Ravel} ravelInstance - An instance of a Ravel application.
                                            * @param {string} name - A unique name for this `DatbaseProvider`. A default can
                                            *                      be provided by overriding this constructor and using ES2015
                                            *                      default argument value syntax. Must be unique within
                                            *                      your application.
                                            */
  constructor(ravelInstance, name) {
    this[sName] = name;
    this.log = ravelInstance.log.getLogger(this.name);

    ravelInstance.once('pre listen', () => {
      ravelInstance.log.debug(`Using DatabaseProvider ${this.constructor.name}, alias: ${this.name}`);
      try {
        this.prelisten(ravelInstance);
      } catch (err) {
        // EventEmitter swallows error otherwise
        ravelInstance.emit('error', err);
      }
    });

    ravelInstance.once('end', () => {
      ravelInstance.log.debug(`Shutting down ${this.constructor.name}, alias: ${this.name}`);
      this.end(ravelInstance);
    });

    if (!ravelInstance[sProviders]) {
      ravelInstance[sProviders] = [];
    }

    ravelInstance[sProviders].push(this);
  }

  /**
     * @returns {string} The unique name of this DatabaseProvider.
     *                  Try to pick something unique within the Ravel ecosystem.
     */
  get name() {
    return this[sName];
  }

  /**
     * Anything that should happen just before a Ravel application starts listening
     * (`app.listen()`) should happen here. If you override this hook, be sure to call `super()`.
     * This function should return nothing. It is a good place to start connection
     * [pools](https://github.com/coopernurse/node-pool).
     *
     * @param {Ravel} ravelInstance - An instance of a Ravel application.
     */
  prelisten(ravelInstance) {} // eslint-disable-line no-unused-vars

  /**
   * Anything that should happen just before a Ravel application stops listening
   * (`app.end()`) should happen here. If you override this hook, be sure to call `super()`.
   * This function should return nothing.
   *
   * @param {Ravel} ravelInstance - An instance of a Ravel application.
   */
  end(ravelInstance) {} // eslint-disable-line no-unused-vars

  /**
   * Obtain a connection and start a transaction.
   *
   * @returns {Promise} Resolved by the open connection.
   */
  getTransactionConnection() {// eslint-disable-line no-unused-vars
    return Promise.reject(new ApplicationError.NotImplemented(
    'DatabaseProvider ' + this.name + ' must implement getTransactionConnection()'));
  }

  /**
     * End a transaction and close the connection.
     * Rollback the transaction iff finalErr !== null.
     *
     * @param {Object} connection - A connection object which was used throughout the transaction.
     * @param {boolean} shouldCommit - If true, commit, otherwise rollback.
     * @returns {Promise} Resolved, or rejected if there was an error while closing the connection.
     */
  exitTransaction(connection, shouldCommit) {// eslint-disable-line no-unused-vars
    return Promise.reject(new ApplicationError.NotImplemented(
    'DatabaseProvider ' + this.name + ' must implement exitTransaction(connection, shouldCommit)'));
  }};


/*!
       * Export accessor for `DatabaseProvider`s list
       */
module.exports = function (Ravel) {
  Ravel.prototype.databaseProviders = function () {
    return this[sProviders] ? this[sProviders] : [];
  };
};

/*!
    * Export the `DatabseProvider` superclass
    */
module.exports.DatabaseProvider = DatabaseProvider;