Merge pull request #658 from wision/multi-servers

Client support multiple servers

Author: jsumners

docs/client.md

@@ -14,7 +14,7 @@ The code to create a new client looks like:
 
     var ldap = require('ldapjs');
     var client = ldap.createClient({
-      url: 'ldap://127.0.0.1:1389'
+      url: ['ldap://127.0.0.1:1389', 'ldap://127.0.0.2:1389']
     });
 
 You can use `ldap://` or `ldaps://`; the latter would connect over SSL (note
@@ -24,7 +24,7 @@ client is:
 
 |Attribute      |Description                                                |
 |---------------|-----------------------------------------------------------|
-|url            |A valid LDAP URL (proto/host/port only)                    |
+|url            |A string or array of valid LDAP URL(s) (proto/host/port)   |
 |socketPath     |Socket path if using AF\_UNIX sockets                      |
 |log            |A compatible logger instance (Default: no-op logger)       |
 |timeout        |Milliseconds client should let operations live for before timing out (Default: Infinity)|
@@ -34,6 +34,13 @@ client is:
 |strictDN       |Force strict DN parsing for client methods (Default is true)|
 |reconnect      |Try to reconnect when the connection gets lost (Default is false)|
 
+### url
+This parameter takes a single connection string or an array of connection strings
+as an input. In case an array is provided, the client tries to connect to the
+servers in given order. To achieve random server strategy (e.g. to distribute
+the load among the servers), please shuffle the array before passing it as an
+argument.
+
 ### Note On Logger
 
 A passed in logger is expected to conform to the [Bunyan](https://www.npmjs.com/package/bunyan)

lib/client/client.js

@@ -110,12 +110,13 @@ function Client (options) {
   EventEmitter.call(this, options)
 
   var self = this
-  var _url
-  if (options.url) { _url = url.parse(options.url) }
-  this.host = _url ? _url.hostname : undefined
-  this.port = _url ? _url.port : false
-  this.secure = _url ? _url.secure : false
-  this.url = _url
+  this.urls = options.url ? [].concat(options.url).map(url.parse) : []
+  this._nextServer = 0
+  // updated in connectSocket() after each connect
+  this.host = undefined
+  this.port = undefined
+  this.secure = undefined
+  this.url = undefined
   this.tlsOptions = options.tlsOptions
   this.socketPath = options.socketPath || false
 
@@ -792,6 +793,9 @@ Client.prototype.connect = function connect () {
 
   // Establish basic socket connection
   function connectSocket (cb) {
+    var server = self.urls[self._nextServer]
+    self._nextServer = (self._nextServer + 1) % self.urls.length
+
     cb = once(cb)
 
     function onResult (err, res) {
@@ -820,16 +824,17 @@ Client.prototype.connect = function connect () {
       setupClient(cb)
     }
 
-    var port = (self.port || self.socketPath)
-    if (self.secure) {
-      socket = tls.connect(port, self.host, self.tlsOptions)
+    var port = (server && server.port) || self.socketPath
+    var host = server && server.hostname
+    if (server && server.secure) {
+      socket = tls.connect(port, host, self.tlsOptions)
       socket.once('secureConnect', onConnect)
     } else {
-      socket = net.connect(port, self.host)
+      socket = net.connect(port, host)
       socket.once('connect', onConnect)
     }
     socket.once('error', onResult)
-    initSocket()
+    initSocket(server)
 
     // Setup connection timeout handling, if desired
     if (self.connectTimeout) {
@@ -844,9 +849,9 @@ Client.prototype.connect = function connect () {
   }
 
   // Initialize socket events and LDAP parser.
-  function initSocket () {
+  function initSocket (url) {
     tracker = messageTrackerFactory({
-      id: self.url ? self.url.href : self.socketPath,
+      id: url ? url.href : self.socketPath,
       parser: new Parser({ log: log })
     })
 
@@ -965,6 +970,13 @@ Client.prototype.connect = function connect () {
       self.emit('socketTimeout')
       socket.end()
     })
+
+    var server = self.urls[self._nextServer]
+    if (server) {
+      self.host = server.hostname
+      self.port = server.port
+      self.secure = server.secure
+    }
   }
 
   var retry
@@ -975,12 +987,15 @@ Client.prototype.connect = function connect () {
       maxDelay: this.reconnect.maxDelay
     })
     failAfter = this.reconnect.failAfter
+    if (this.urls.length > 1 && failAfter) {
+      failAfter *= this.urls.length
+    }
   } else {
     retry = backoff.exponential({
       initialDelay: 1,
       maxDelay: 2
     })
-    failAfter = 1
+    failAfter = this.urls.length || 1
   }
   retry.failAfter(failAfter)
 

lib/client/index.js

@@ -7,7 +7,7 @@ module.exports = {
   Client: Client,
   createClient: function createClient (options) {
     if (isObject(options) === false) throw TypeError('options (object) required')
-    if (options.url && typeof options.url !== 'string') throw TypeError('options.url (string) required')
+    if (options.url && typeof options.url !== 'string' && !Array.isArray(options.url)) throw TypeError('options.url (string|array) required')
     if (options.socketPath && typeof options.socketPath !== 'string') throw TypeError('options.socketPath must be a string')
     if ((options.url && options.socketPath) || !(options.url || options.socketPath)) throw TypeError('options.url ^ options.socketPath (String) required')
     if (!options.log) options.log = logger

test/client.test.js

@@ -340,10 +340,9 @@ tap.test('createClient', t => {
     t.throws(() => ldap.createClient(42), match)
   })
 
-  t.test('url must be a string', async t => {
-    const match = /options\.url \(string\) required/
+  t.test('url must be a string or array', async t => {
+    const match = /options\.url \(string\|array\) required/
     t.throws(() => ldap.createClient({ url: {} }), match)
-    t.throws(() => ldap.createClient({ url: [] }), match)
     t.throws(() => ldap.createClient({ url: 42 }), match)
   })
 
@@ -379,6 +378,20 @@ tap.test('createClient', t => {
     }
   })
 
+  t.test('url array is correctly assigned', async t => {
+    getPort().then(function (unusedPortNumber) {
+      const client = ldap.createClient({
+        url: [
+          `ldap://127.0.0.1:${unusedPortNumber}`,
+          `ldap://127.0.0.2:${unusedPortNumber}`
+        ],
+        connectTimeout: 1
+      })
+
+      t.equal(client.urls.length, 2)
+    })
+  })
+
   // TODO: this test is really flaky. It would be better if we could validate
   // the options _withouth_ having to connect to a server.
   // t.test('attaches a child function to logger', async t => {