@mysql/xdevapi
Version:
MySQL Connector/Node.js - A Node.js driver for MySQL using the X Protocol and X DevAPI.
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JavaScript
/*
* Copyright (c) 2018, 2022, Oracle and/or its affiliates.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License, version 2.0, as
* published by the Free Software Foundation.
*
* This program is also distributed with certain software (including
* but not limited to OpenSSL) that is licensed under separate terms,
* as designated in a particular file or component or in included license
* documentation. The authors of MySQL hereby grant you an
* additional permission to link the program and your derivative works
* with the separately licensed software that they have included with
* MySQL.
*
* Without limiting anything contained in the foregoing, this file,
* which is part of MySQL Connector/Node.js, is also subject to the
* Universal FOSS Exception, version 1.0, a copy of which can be found at
* http://oss.oracle.com/licenses/universal-foss-exception.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU General Public License, version 2.0, for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
;
const connection = require('./PoolConnection');
const errors = require('../constants/errors');
const system = require('../system');
const util = require('util');
const { isValidBoolean, isValidInteger } = require('../validator');
/**
* XDevAPI implementation of a connection pool. Should be used via the {@link module:Client|Client} API.
* @module ConnectionPool
* @example
* const pool = mysqlx.getClient('mysqlx://root@localhost', {
* pooling: {
* enabled: true,
* maxSize: 10,
* maxIdleTime: 20000,
* queueTimeout: 5000
* }
* })
*
* pool.getSession()
* .then(session => {
* // A new session is created using a connection from the pool.
* })
*/
/**
* Connection pool configuration properties.
* @typedef {Object} Properties
* @prop {boolean} [enabled=true] - use a connection pool
* @prop {number} [maxSize=25] - maximum number of connections in the pool
* @prop {number} [maxIdleTime=0] - maximum number of milliseconds to allow a connection to be idle (0 - infinite)
* @prop {number} [queueTimeout=0] - maximum number of milliseconds to wait for a connection to become available (0 - infinite)
*/
const VALID_OPTIONS = ['enabled', 'maxIdleTime', 'maxSize', 'queueTimeout'];
/**
* @private
* @alias module:ConnectionPool
* @param {Object} [options] - pooling options
* @returns {module:ConnectionPool}
*/
function ConnectionPool (options = {}) {
// Internal pool state containing a list of connections
// given their current state.
const state = {
// Contains the list of active connections i.e. that have not been
// closed neither by the client nor the server.
active: [],
// Informs if the pool is avaiable or not. After it starts to be
// destroyed, it should become unavailable.
available: true,
// Contains the list of connections that have expired i.e. where
// maxIdleTime was exceeded or have been closed by the server.
expired: [],
// Contains the list of connections that became idle i.e. have been
// closed by the client.
idle: [],
// Keep track of the number of reserved slots in order to ensure
// connections are only created when there is space in the pool.
tickets: 0
};
return {
/**
* Returns the current list of active connections in the pool.
* @private
* @function
* @name module:ConnectionPool#activeConnections
* @returns {Array<PoolConnection>} The list of connection instances.
*/
activeConnections () {
return state.active;
},
/**
* Returns the current list of idle connections in the pool.
* @private
* @function
* @name module:ConnectionPool#idleConnections
* @param {Object} [state={}] - The initial state of the pool.
* @param {Array<PoolConnection>} [state.active=[]] - A list of active connections
* @param {Array<PoolConnection>} [state.idle=[]] - A list of idle connections
* @param {Array<PoolConnection>} [state.expired=[]] - A list of expired connections.
* @returns {ConnectionPool} The pool instance.
*/
create ({ active = [], expired = [], idle = [] } = {}) {
state.active = active;
state.available = true;
state.expired = expired;
state.idle = idle;
state.tickets = active.length;
return this;
},
/**
* Close all the connections in the pool.
* @private
* @function
* @name module:ConnectionPool#destroy
* @returns {Promise}
*/
destroy () {
// We should put the pool in a state that prevents queued
// connection requests from being fulfilled.
state.available = false;
// Expired connections have already been destroyed by this point.
return Promise.all(state.idle.concat(state.active).map(con => con.destroy()))
.then(() => {
return this.reset();
})
.catch(err => {
this.reset();
throw err;
});
},
/**
* Returns the current list of expired connections in the pool.
* @private
* @function
* @name module:ConnectionPool#expiredConnections
* @returns {Array<PoolConnection>} The list of connection instances.
*/
expiredConnections () {
return state.expired;
},
/**
* Retrieve a usable connection from the pool.
* If there are idle connections available on is returned.
* If there are no idle connections available and the pool is not
* full, either an expired connection is re-created or a new
* connection is created.
* If the pool is full, it will wait until queueTimeout is reached.
* Every time this function is called, the list of connections
* is updated according to the status of each connection.
* @private
* @function
* @name module:ConnectionPool#getConnection
* @throws Will return a rejected Promise if queueTimeout is exceeded.
* @returns {Promise<PoolConnection>}
*/
getConnection (requestedAt = system.time()) {
return this.update()
.then(() => {
// If previous connection requests were queued and the
// pool is closed or being closed, we should not try to
// create, refurbish or re-use connections at the risk of
// leaving a system socket open which will be not cleaned
// up after the process finishes, leading to a resource
// leak. There is nothing else left to do.
if (!this.isAvailable()) {
return;
}
const elapsedTime = system.time() - requestedAt;
const queueTimeout = options.pooling.queueTimeout;
const postConnect = con => {
// The connection needs to be blocked from being released.
con.acquire();
// The connection should be moved to the active list.
state.active.push(con);
// And returned back to the X DevAPI client.
return con;
};
// Use an existing connection or create a new one.
// If the pool is full, it means the idle and expired
// queues are empty and the connection will be undefined.
const con = state.idle.shift() || state.expired.shift();
// If the pool is full (all the connections are active) we
// need to check if the time elapsed since the previous
// attempt to retrieve the connection from the pool. If
// it exceeds the value of queueTimeout we need to throw
// an error. However, if queueTimeout = 0 that means it
// is supposed to be infinite, so, in that case, we do not
// throw an error and need to try indefinitely.
if (this.isFull() && queueTimeout !== 0 && elapsedTime >= queueTimeout) {
throw new Error(util.format(errors.MESSAGES.ER_DEVAPI_POOL_QUEUE_TIMEOUT, queueTimeout));
}
// If the pool is full and the elapsed time since the last
// attempt to retrieve the connection does not exceed the
// value of queueTimeout (which can be infinite), we need
// to attempt to retrieve the connection again, given a
// proper sliding window. In this case, the next attempt
// will happen only after the same time it passed since
// the last check.
// If the connection is expired but is still being closed,
// which can happen with parallel connection requests, we
// also need to queue the request.
if (this.isFull() || (con && con.isClosing())) {
return new Promise((resolve, reject) => setTimeout(() => this.getConnection(requestedAt).then(resolve).catch(reject), elapsedTime));
}
// Given the connection is only considered active after it
// is effectively created. Due to the asynchronous nature
// of the pool, in the presence of parallel connection
// requests, we need to create a ticket for each
// connection that can and will start to be created.
state.tickets += 1;
// If there is an idle connection which has not been
// closed and has not expired ("maxIdleTime" still has
// not been exceeded) we can re-use it.
if (con && con.isOpen() && !con.isExpired()) {
return con.override().then(postConnect);
}
// If the connection is not open or has expired, we need
// to refurbish the same instance, to ensure the endpoint
// availability is up-to-date.
if (con) {
return con.open().then(postConnect);
}
// Otherwise we need to create a new one.
return connection(options).open().then(postConnect);
});
},
/**
* Returns the current list of idle connections in the pool.
* @private
* @function
* @name module:ConnectionPool#idleConnections
* @returns {Array<PoolConnection>} The list of connection instances.
*/
idleConnections () {
return state.idle;
},
/**
* Checks if the pool is being closed.
* @private
* @function
* @name module:ConnectionPool#isAvailable
* @returns {boolean}
*/
isAvailable () {
return state.available;
},
/**
* Checks if a pool is full i.e. a total of "maxSize" number of
* connections are currently active.
* @private
* @function
* @name module:ConnectionPool#isFull
* @returns {boolean}
*/
isFull () {
// A connection pool is full if the current number of tickets is
// equal to the maximum size of the pool.
return state.tickets === options.pooling.maxSize;
},
/**
* Reset the pool state.
* @private
* @function
* @name module:ConnectionPool#reset
* @returns {module:ConnectionPool} The pool instance.
*/
reset () {
state.active = [];
// The original pool instance will never be available again.
// A new one should be created by the client wrapper.
state.available = false;
state.expired = [];
state.idle = [];
state.tickets = 0;
return this;
},
/**
* Update the list of connections given their current state.
* @private
* @function
* @name module:ConnectionPool#update
* @returns {Promise}
*/
update () {
// A connection can be closed from the server side, which means
// there is a chance that the active connection queue contains
// connections that have been closed. If that is the case, those
// should become expired.
const openActiveConnections = state.active.filter(c => c.isOpen());
const closedActiveConnections = state.active.filter(c => !c.isOpen());
const releasedActiveConnections = state.active.filter(c => c.isIdle());
state.expired = state.expired.concat(closedActiveConnections);
state.active = openActiveConnections;
// The number of reserved slots should decrease given the
// number of connections that are no longer active.
state.tickets = state.tickets - closedActiveConnections.length - releasedActiveConnections.length;
// Active connections that have been closed by the application
// should be released back into the pool, which means they become
// idle.
const validActiveConnections = state.active.filter(c => !c.isIdle());
state.idle = state.idle.concat(releasedActiveConnections);
state.active = validActiveConnections;
// Idle connections can also have expired (when "maxIdleTime" has
// been exceeded).
const expiredIdleConnections = state.idle.filter(c => c.isExpired());
const validIdleConnections = state.idle.filter(c => !c.isExpired());
state.expired = state.expired.concat(expiredIdleConnections);
state.idle = validIdleConnections;
// Expired connections should be destroyed.
return Promise.all(state.expired.map(con => con.destroy()));
}
};
}
ConnectionPool.validate = function (options) {
const invalidKeys = Object.keys(options).filter(k => VALID_OPTIONS.indexOf(k) === -1);
if (invalidKeys.length) {
throw new Error(util.format(errors.MESSAGES.ER_DEVAPI_BAD_CLIENT_OPTION, `pooling.${invalidKeys[0]}`));
}
const { enabled, maxIdleTime, maxSize, queueTimeout } = options;
if (!isValidBoolean({ value: enabled })) {
throw new Error(util.format(errors.MESSAGES.ER_DEVAPI_BAD_CLIENT_OPTION_VALUE, 'pooling.enabled', enabled));
}
if (!isValidInteger({ value: maxIdleTime, min: 0 })) {
throw new Error(util.format(errors.MESSAGES.ER_DEVAPI_BAD_CLIENT_OPTION_VALUE, 'pooling.maxIdleTime', maxIdleTime));
}
if (!isValidInteger({ value: maxSize, min: 1 })) {
throw new Error(util.format(errors.MESSAGES.ER_DEVAPI_BAD_CLIENT_OPTION_VALUE, 'pooling.maxSize', maxSize));
}
if (!isValidInteger({ value: queueTimeout, min: 0 })) {
throw new Error(util.format(errors.MESSAGES.ER_DEVAPI_BAD_CLIENT_OPTION_VALUE, 'pooling.queueTimeout', queueTimeout));
}
return true;
};
ConnectionPool.VALID_OPTIONS = VALID_OPTIONS;
module.exports = ConnectionPool;