'use strict';
|
|
/**
|
* The **ReadPreference** class is a class that represents a MongoDB ReadPreference and is
|
* used to construct connections.
|
* @class
|
* @param {string} mode A string describing the read preference mode (primary|primaryPreferred|secondary|secondaryPreferred|nearest)
|
* @param {array} tags The tags object
|
* @param {object} [options] Additional read preference options
|
* @param {number} [options.maxStalenessSeconds] Max secondary read staleness in seconds, Minimum value is 90 seconds.
|
* @see https://docs.mongodb.com/manual/core/read-preference/
|
* @return {ReadPreference}
|
*/
|
const ReadPreference = function(mode, tags, options) {
|
if (!ReadPreference.isValid(mode)) {
|
throw new TypeError(`Invalid read preference mode ${mode}`);
|
}
|
|
// TODO(major): tags MUST be an array of tagsets
|
if (tags && !Array.isArray(tags)) {
|
console.warn(
|
'ReadPreference tags must be an array, this will change in the next major version'
|
);
|
|
if (typeof tags.maxStalenessSeconds !== 'undefined') {
|
// this is likely an options object
|
options = tags;
|
tags = undefined;
|
} else {
|
tags = [tags];
|
}
|
}
|
|
this.mode = mode;
|
this.tags = tags;
|
|
options = options || {};
|
if (options.maxStalenessSeconds != null) {
|
if (options.maxStalenessSeconds <= 0) {
|
throw new TypeError('maxStalenessSeconds must be a positive integer');
|
}
|
|
this.maxStalenessSeconds = options.maxStalenessSeconds;
|
|
// NOTE: The minimum required wire version is 5 for this read preference. If the existing
|
// topology has a lower value then a MongoError will be thrown during server selection.
|
this.minWireVersion = 5;
|
}
|
|
if (this.mode === ReadPreference.PRIMARY) {
|
if (this.tags && Array.isArray(this.tags) && this.tags.length > 0) {
|
throw new TypeError('Primary read preference cannot be combined with tags');
|
}
|
|
if (this.maxStalenessSeconds) {
|
throw new TypeError('Primary read preference cannot be combined with maxStalenessSeconds');
|
}
|
}
|
};
|
|
// Support the deprecated `preference` property introduced in the porcelain layer
|
Object.defineProperty(ReadPreference.prototype, 'preference', {
|
enumerable: true,
|
get: function() {
|
return this.mode;
|
}
|
});
|
|
/*
|
* Read preference mode constants
|
*/
|
ReadPreference.PRIMARY = 'primary';
|
ReadPreference.PRIMARY_PREFERRED = 'primaryPreferred';
|
ReadPreference.SECONDARY = 'secondary';
|
ReadPreference.SECONDARY_PREFERRED = 'secondaryPreferred';
|
ReadPreference.NEAREST = 'nearest';
|
|
const VALID_MODES = [
|
ReadPreference.PRIMARY,
|
ReadPreference.PRIMARY_PREFERRED,
|
ReadPreference.SECONDARY,
|
ReadPreference.SECONDARY_PREFERRED,
|
ReadPreference.NEAREST,
|
null
|
];
|
|
/**
|
* Construct a ReadPreference given an options object.
|
*
|
* @param {object} options The options object from which to extract the read preference.
|
* @return {ReadPreference}
|
*/
|
ReadPreference.fromOptions = function(options) {
|
const readPreference = options.readPreference;
|
const readPreferenceTags = options.readPreferenceTags;
|
|
if (readPreference == null) {
|
return null;
|
}
|
|
if (typeof readPreference === 'string') {
|
return new ReadPreference(readPreference, readPreferenceTags);
|
} else if (!(readPreference instanceof ReadPreference) && typeof readPreference === 'object') {
|
const mode = readPreference.mode || readPreference.preference;
|
if (mode && typeof mode === 'string') {
|
return new ReadPreference(mode, readPreference.tags, {
|
maxStalenessSeconds: readPreference.maxStalenessSeconds
|
});
|
}
|
}
|
|
return readPreference;
|
};
|
|
/**
|
* Validate if a mode is legal
|
*
|
* @method
|
* @param {string} mode The string representing the read preference mode.
|
* @return {boolean} True if a mode is valid
|
*/
|
ReadPreference.isValid = function(mode) {
|
return VALID_MODES.indexOf(mode) !== -1;
|
};
|
|
/**
|
* Validate if a mode is legal
|
*
|
* @method
|
* @param {string} mode The string representing the read preference mode.
|
* @return {boolean} True if a mode is valid
|
*/
|
ReadPreference.prototype.isValid = function(mode) {
|
return ReadPreference.isValid(typeof mode === 'string' ? mode : this.mode);
|
};
|
|
const needSlaveOk = ['primaryPreferred', 'secondary', 'secondaryPreferred', 'nearest'];
|
|
/**
|
* Indicates that this readPreference needs the "slaveOk" bit when sent over the wire
|
* @method
|
* @return {boolean}
|
* @see https://docs.mongodb.com/manual/reference/mongodb-wire-protocol/#op-query
|
*/
|
ReadPreference.prototype.slaveOk = function() {
|
return needSlaveOk.indexOf(this.mode) !== -1;
|
};
|
|
/**
|
* Are the two read preference equal
|
* @method
|
* @param {ReadPreference} readPreference The read preference with which to check equality
|
* @return {boolean} True if the two ReadPreferences are equivalent
|
*/
|
ReadPreference.prototype.equals = function(readPreference) {
|
return readPreference.mode === this.mode;
|
};
|
|
/**
|
* Return JSON representation
|
* @method
|
* @return {Object} A JSON representation of the ReadPreference
|
*/
|
ReadPreference.prototype.toJSON = function() {
|
const readPreference = { mode: this.mode };
|
if (Array.isArray(this.tags)) readPreference.tags = this.tags;
|
if (this.maxStalenessSeconds) readPreference.maxStalenessSeconds = this.maxStalenessSeconds;
|
return readPreference;
|
};
|
|
/**
|
* Primary read preference
|
* @member
|
* @type {ReadPreference}
|
*/
|
ReadPreference.primary = new ReadPreference('primary');
|
/**
|
* Primary Preferred read preference
|
* @member
|
* @type {ReadPreference}
|
*/
|
ReadPreference.primaryPreferred = new ReadPreference('primaryPreferred');
|
/**
|
* Secondary read preference
|
* @member
|
* @type {ReadPreference}
|
*/
|
ReadPreference.secondary = new ReadPreference('secondary');
|
/**
|
* Secondary Preferred read preference
|
* @member
|
* @type {ReadPreference}
|
*/
|
ReadPreference.secondaryPreferred = new ReadPreference('secondaryPreferred');
|
/**
|
* Nearest read preference
|
* @member
|
* @type {ReadPreference}
|
*/
|
ReadPreference.nearest = new ReadPreference('nearest');
|
|
module.exports = ReadPreference;
|
