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131 lines
3.9 KiB
131 lines
3.9 KiB
"use strict";
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/**
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* @fileOverview The **ReadPreference** class is a class that represents a MongoDB ReadPreference and is
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* used to construct connections.
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*
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* @example
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* var Db = require('mongodb').Db,
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* ReplSet = require('mongodb').ReplSet,
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* Server = require('mongodb').Server,
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* ReadPreference = require('mongodb').ReadPreference,
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* test = require('assert');
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* // Connect using ReplSet
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* var server = new Server('localhost', 27017);
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* var db = new Db('test', new ReplSet([server]));
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* db.open(function(err, db) {
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* test.equal(null, err);
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* // Perform a read
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* var cursor = db.collection('t').find({});
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* cursor.setReadPreference(ReadPreference.PRIMARY);
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* cursor.toArray(function(err, docs) {
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* test.equal(null, err);
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* db.close();
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* });
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* });
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*/
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/**
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* Creates a new ReadPreference instance
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*
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* Read Preferences
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* - **ReadPreference.PRIMARY**, Read from primary only. All operations produce an error (throw an exception where applicable) if primary is unavailable. Cannot be combined with tags (This is the default.).
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* - **ReadPreference.PRIMARY_PREFERRED**, Read from primary if available, otherwise a secondary.
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* - **ReadPreference.SECONDARY**, Read from secondary if available, otherwise error.
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* - **ReadPreference.SECONDARY_PREFERRED**, Read from a secondary if available, otherwise read from the primary.
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* - **ReadPreference.NEAREST**, All modes read from among the nearest candidates, but unlike other modes, NEAREST will include both the primary and all secondaries in the random selection.
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*
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* @class
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* @param {string} mode The ReadPreference mode as listed above.
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* @param {array|object} tags An object representing read preference tags.
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* @param {object} [options] Additional read preference options
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* @param {number} [options.maxStalenessSeconds] Max Secondary Read Staleness in Seconds
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* @return {ReadPreference} a ReadPreference instance.
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*/
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var ReadPreference = function(mode, tags, options) {
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if(!(this instanceof ReadPreference)) {
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return new ReadPreference(mode, tags, options);
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}
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this._type = 'ReadPreference';
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this.mode = mode;
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this.tags = tags;
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this.options = options;
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// If no tags were passed in
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if(tags && typeof tags == 'object' && !Array.isArray(tags)) {
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if(tags.maxStalenessSeconds) {
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this.options = tags;
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this.tags = null;
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}
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}
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// Add the maxStalenessSeconds value to the read Preference
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if(this.options && this.options.maxStalenessSeconds) {
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this.maxStalenessSeconds = this.options.maxStalenessSeconds;
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}
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}
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/**
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* Validate if a mode is legal
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*
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* @method
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* @param {string} mode The string representing the read preference mode.
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* @return {boolean}
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*/
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ReadPreference.isValid = function(_mode) {
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return (_mode == ReadPreference.PRIMARY || _mode == ReadPreference.PRIMARY_PREFERRED
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|| _mode == ReadPreference.SECONDARY || _mode == ReadPreference.SECONDARY_PREFERRED
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|| _mode == ReadPreference.NEAREST
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|| _mode == true || _mode == false || _mode == null);
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}
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/**
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* Validate if a mode is legal
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*
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* @method
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* @param {string} mode The string representing the read preference mode.
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* @return {boolean}
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*/
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ReadPreference.prototype.isValid = function(mode) {
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var _mode = typeof mode == 'string' ? mode : this.mode;
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return ReadPreference.isValid(_mode);
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}
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/**
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* @ignore
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*/
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ReadPreference.prototype.toObject = function() {
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var object = {mode:this.mode};
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if(this.tags != null) {
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object['tags'] = this.tags;
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}
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if(this.maxStalenessSeconds) {
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object['maxStalenessSeconds'] = this.maxStalenessSeconds;
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}
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return object;
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}
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/**
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* @ignore
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*/
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ReadPreference.prototype.toJSON = function() {
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return this.toObject();
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}
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/**
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* @ignore
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*/
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ReadPreference.PRIMARY = 'primary';
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ReadPreference.PRIMARY_PREFERRED = 'primaryPreferred';
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ReadPreference.SECONDARY = 'secondary';
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ReadPreference.SECONDARY_PREFERRED = 'secondaryPreferred';
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ReadPreference.NEAREST = 'nearest'
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/**
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* @ignore
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*/
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module.exports = ReadPreference;
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