我是Node / Express的新手，我正在预约系统。我希望我的用户预约他们想要的那一天，我的系统会在那个确切的时间向他们发送通知。我发现“node-schedule”模块对这个任务非常有用，但我不知道在哪里实现它。无论如何都要在我的app.js中存储所有任务，或者只是在每次达到某个终点时创建一个节点计划任务就足够了，例如：
router.get('/', function(req, res, next) {
var j = schedule.scheduleJob(date, function(){
send notification();
});
res.send(200);
}
注意：我不想在我的sql表上运行常量for循环来检查日期
答案 0 :(得分：8)
您需要将应用程序数据保存到某种形式的永久存储中，方法是使用类似SQLite的文件写入本地文件，运行您自己的数据库服务器（如MongoDB）或使用云基于Amazon SimpleDb的存储服务。
这些选项（以及许多其他选项）中的每一个都有npm模块，可用于读取/写入/删除持久数据。有关示例，请参阅MongoDb上使用npm提供的SQLite3，SimpleDb和npmjs.com。
根据您的评论如下：嗯，您确实询问了可以存储预定活动的位置。 ;）
要保留所有计划事件以使它们在可能的服务器故障中存活，您需要创建一个可存储的数据结构来表示它们，并为每个事件创建表示的新实例并将其存储到持久存储（MySQL）
通常情况下，你会使用以下内容：
{
when:DateTime -- timestamp when the event should fire
what:Action -- what this event should do
args:Arguments -- arguments to pass to Action
pending:Boolean=true -- if false, this event has already fired
}
初始化服务器时，您将查询持久存储中pending===true的所有事件，并使用结果初始化node-schedule模块的实例。
当您需要在服务器运行时安排新事件时，您将创建一个新的事件表示，将其写入持久存储并使用它创建node-schedule的新实例。
最后，，最重要的是为了客户的幸福，当预定事件成功完成时，就在您的事件处理程序（上面提到的Action）完成之前，它需要标记持久性它作为pending:false处理的事件的版本，因此您不会多次触发任何事件。
例如：
'use strict';
var scheduler = require('node-schedule');
/**
* Storable Representation of a Scheduled Event
*
* @param {string|Date} when
* @param {string} what
* @param {array.<string>} [args=[]]
* @param {boolean} [pending=true]
*
* @property {Date} PersistentEvent.when - the datetime this event should fire.
* @property {string} PersistentEvent.what - the name of the action to run (must match key of PersistentEvent.Actions)
* @property {array} PersistentEvent.args - args to pass to action event handler.
* @property {boolean} PersistentEvent.pending - if true, this event has not yet fired.
*
* @constructor
*
* @example
*
* var PersistentEvent = require('PersistentEvent'),
* mysql = require('mysql'),
* conn = mysql.createConnection({ ... });
*
* conn.connect();
*
* // at some point when initializing your app...
*
* // assign your persistent storage connection...
* PersistentEvent.setStore(conn);
*
* // load all pending event from persistent storage...
* PersistentEvent.loadAll$(function (err) {
* if (err) {
* throw new Error('failed to load all PersistentEvents: ' + err);
* }
*
* // from this point on, all persistent events are loaded and running.
*
* });
*/
var PersistentEvent = function (when, what, args, pending) {
// initialize
PersistentEvent.Cache.push(this.init({
when: when,
what: what,
args: args,
pending: pending
}));
};
// ==== PersistentEvent Static Methods ====
/**
* Pre-defined action event handlers.
* <p>
* Where the property key will be used to match the PersistentEvent.what property,
* and the property value is a event handler function that accepts an optional
* array of args and a callback (provided by PersistentEvent.prototype.schedule)
* </p>
*
* @property {object}
* @property {function} Actions.doSomething
* @property {function} Actions.doSomethingElse
*
* @static
*/
PersistentEvent.Actions = {
doSomething: function (args, cb) {
// defaults
args = args || [];
// TODO check specific args here ...
var result = true,
err = null;
// do your action here, possibly with passed args
cb(err, result);
},
doSomethingElse: function (args, cb) {
// defaults
args = args || [];
// TODO check specific args here ...
var result = true,
err = null;
// do your action here, possibly with passed args
cb(err, result);
}
};
/**
* Cache of all PersistentEvents
*
* @type {Array.<PersistentEvent>}
* @static
*/
PersistentEvent.Cache = [];
// Data Management
/**
* Connection to persistent storage.
* TODO - This should be abstracted to handle other engines that MySQL.
* @property {object}
* @static
*/
PersistentEvent.StorageConnection = null;
/**
* Sets the storage connection used to persist events.
*
* @param {object} storageConnection
* @static
*/
PersistentEvent.setStore = function (storageConnection) { // set the persistent storage connection
// TODO - check args here...
// Note: this function isn't really needed unless you're using other kinds of storage engines
// where you'd want to test what engine was used and mutate this interface accordingly.
PersistentEvent.StorageConnection = storageConnection;
};
/**
* Saves a PersistentEvent to StorageConnection.
*
* @param {PersistentEvent} event - event to save
* @param {function} cb - callback on complete
* @static
*/
PersistentEvent.save$ = function (event, cb) {
var conn = PersistentEvent.StorageConnection;
if (null === conn) {
throw new Error('requires a StorageConnection');
}
// TODO - check for active connection here...
// TODO - check args here...
conn.query('INSERT INTO TABLE when = :when, what = :what, args = :args, pending = :pending', event, cb);
};
/**
* Loads all PersistentEvents from StorageConnection.
* @param {function} cb -- callback on complete
* @static
*/
PersistentEvent.loadAll$ = function (cb) {
var conn = PersistentEvent.StorageConnection;
if (null === conn) {
throw new Error('requires a StorageConnection');
}
// check for active connection here...
// check args here...
conn.query('QUERY * FROM TABLE WHERE pending = true', function (err, results) {
if (err) {
return cb(err);
}
results.forEach(function (result) {
// TODO: check for existence of required fields here...
var event = new PersistentEvent(result.when, result.what, result.args, true);
event.schedule();
});
cb(null);
});
};
// ==== PersistentEvent Methods ====
/**
* Initialize an instance of PersistentEvent.
*
* @param {object} opts
* @return {PersistentEvent}
*/
Event.prototype.init = function (opts) {
// check args
if ('object' !== typeof opts) {
throw new Error('opts must be an object');
}
// set defaults
opts.args = opts.args || [];
opts.pending = opts.pending || true;
// convert string to Date, if required
if ('string' === typeof opts.when) {
opts.when = new Date(opts.when);
}
// check that opts contains needed properties
if (!opts.when instanceof Date) {
throw new Error('when must be a string representation of a Date or a Date object');
}
if ('string' !== typeof opts.what) {
throw new Error('what must be a string containing an action name');
}
if (!Array.isArray(opts.args)) {
throw new Error('args must be an array');
}
if ('boolean' !== typeof opts.pending) {
throw new Error('pending must be a boolean');
}
// set our properties
var self = this;
Object.keys(opts).forEach(function (key) {
if (opts.hasOwnProperty(key)) {
self = opts[key];
}
});
return this;
};
/**
* Override for Object.toString()
* @returns {string}
*/
PersistentEvent.prototype.toString = function () {
return JSON.stringify(this);
};
/**
* Schedule the event to run.<br/>
* <em>Side-effect: saves event to persistent storage.</em>
*/
PersistentEvent.prototype.schedule = function () {
var self = this,
handler = Actions[this.what];
if ('function' !== typeof handler) {
throw new Error('no handler found for action:' + this.what);
}
PersistentEvent.save$(self, function () {
self._event = scheduler.scheduleJob(self.when, function () {
handler(self.args, function (err, result) {
if (err) {
console.error('event ' + self + ' failed:' + err);
}
self.setComplete();
});
});
});
};
/**
* Sets this event complete.<br/>
* <em>Side-effect: saves event to persistent storage.</em>
*/
PersistentEvent.prototype.setComplete = function () {
var self = this;
delete this._event;
this.pending = false;
PersistentEvent.save$(this, function (err) {
if (err) {
console.error('failed to save event ' + self + ' :' + err);
}
});
};
请注意，这是一个首次通过样板，向您展示设计问题解决方案的一种方法。它将需要您进一步努力才能运行。
答案 1 :(得分：2)
你可以每天早上做一个cron工作，选择当天的所有约会并安排推送。这样，在服务器负载最小的时候，您也必须一次查询数据库。