Client support multiple servers

Author: Martin Cizek

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://127.0.0.1:1389,127.0.0.2:1389'
     });
 
 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 valid LDAP URL(s) (proto/host(s)/port(s)                 |
 |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)|

lib/client/client.js

@@ -110,12 +110,17 @@ 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.servers = []
+  if (options.url) {
+    var [, protocol, hosts, path] = options.url.match(/^([a-zA-Z]+:\/\/)([^/]*)(.*)/)
+
+    hosts.split(',').forEach((host) => {
+      this.servers.push(url.parse(`${protocol}${host}${path}`))
+    })
+  }
+
+  // select random server at the start
+  this.nextServer = Math.floor(Math.random() * this.servers.length)
   this.tlsOptions = options.tlsOptions
   this.socketPath = options.socketPath || false
 
@@ -792,6 +797,8 @@ Client.prototype.connect = function connect () {
 
   // Establish basic socket connection
   function connectSocket (cb) {
+    self.nextServer = (self.nextServer + 1) % self.servers.length
+    self.url = self.servers[self.nextServer]
     cb = once(cb)
 
     function onResult (err, res) {
@@ -820,12 +827,13 @@ Client.prototype.connect = function connect () {
       setupClient(cb)
     }
 
-    var port = (self.port || self.socketPath)
+    var port = (self.servers.length && self.servers[self.nextServer].port) || self.socketPath
+    var hostname = (self.servers.length && self.servers[self.nextServer].hostname) || undefined
     if (self.secure) {
-      socket = tls.connect(port, self.host, self.tlsOptions)
+      socket = tls.connect(port, hostname, self.tlsOptions)
       socket.once('secureConnect', onConnect)
     } else {
-      socket = net.connect(port, self.host)
+      socket = net.connect(port, hostname)
       socket.once('connect', onConnect)
     }
     socket.once('error', onResult)
@@ -975,6 +983,9 @@ Client.prototype.connect = function connect () {
       maxDelay: this.reconnect.maxDelay
     })
     failAfter = this.reconnect.failAfter
+    if (this.servers.length > 1 && failAfter) {
+      failAfter *= this.servers.length
+    }
   } else {
     retry = backoff.exponential({
       initialDelay: 1,