Connection: allow more keepalive configuration

README.md

@@ -394,7 +394,10 @@ Connection Instance Methods
     * **autotls** - _string_ - Set to 'always' to always attempt connection upgrades via STARTTLS, 'required' only if upgrading is required, or 'never' to never attempt upgrading. **Default:** 'never'
     * **connTimeout** - _integer_ - Number of milliseconds to wait for a connection to be established. **Default:** 10000
     * **authTimeout** - _integer_ - Number of milliseconds to wait to be authenticated after a connection has been established. **Default:** 5000
-    * **keepalive** - _boolean_ - Enable the keepalive mechanism. **Default:** true
+    * **keepalive** - _mixed_ - Configures the keepalive mechanism. Set to `true` to enable keepalive with defaults or set to object to enable and configure keepalive behavior: **Default:** true
+        * **interval** - _integer_ - This is the interval (in milliseconds) at which NOOPs are sent and the interval at which `idleInterval` is checked. **Default:** 10000
+        * **idleInterval** - _integer_ - This is the interval (in milliseconds) at which an IDLE command (for servers that support IDLE) is re-sent. **Default:** 300000 (5 mins)
+        * **forceNoop** - _boolean_ - Set to `true` to force use of NOOP keepalive on servers also support IDLE. **Default:** false
     * **debug** - _function_ - If set, the function will be called with one argument, a string containing some debug info **Default:** (no debug output)
 
 * **connect**() - _(void)_ - Attempts to connect and authenticate with the IMAP server.

lib/Connection.js

@@ -67,9 +67,9 @@ function Connection(config) {
     xoauth2: config.xoauth2,
     connTimeout: config.connTimeout || 10000,
     authTimeout: config.authTimeout || 5000,
-    keepalive: (typeof config.keepalive === 'boolean'
-                ? config.keepalive
-                : true)
+    keepalive: (config.keepalive === undefined || config.keepalive === null
+                ? true
+                : config.keepalive)
   };
 
   this._sock = config.socket || undefined;
@@ -1532,10 +1532,15 @@ Connection.prototype._createCurrentBox = function() {
 
 Connection.prototype._doKeepaliveTimer = function(immediate) {
   var self = this,
+      interval = this._config.keepalive.interval || KEEPALIVE_INTERVAL,
+      idleWait = this._config.keepalive.idleInterval || MAX_IDLE_WAIT,
+      forceNoop = this._config.keepalive.forceNoop || false,
       timerfn = function() {
         if (self._idle.enabled) {
           // unlike NOOP, IDLE is only a valid command after authenticating
-          if (!self.serverSupports('IDLE') || self.state !== 'authenticated')
+          if (!self.serverSupports('IDLE')
+              || self.state !== 'authenticated'
+              || forceNoop)
             self._enqueue('NOOP', true);
           else {
             if (self._idle.started === undefined) {
@@ -1543,14 +1548,14 @@ Connection.prototype._doKeepaliveTimer = function(immediate) {
               self._enqueue('IDLE', true);
             } else if (self._idle.started > 0) {
               var timeDiff = Date.now() - self._idle.started;
-              if (timeDiff >= MAX_IDLE_WAIT) {
+              if (timeDiff >= idleWait) {
                 self._idle.enabled = false;
                 self.debug && self.debug('=> DONE');
                 self._sock.write('DONE' + CRLF);
                 return;
               }
             }
-            self._tmrKeepalive = setTimeout(timerfn, KEEPALIVE_INTERVAL);
+            self._tmrKeepalive = setTimeout(timerfn, interval);
           }
         }
       };
@@ -1558,7 +1563,7 @@ Connection.prototype._doKeepaliveTimer = function(immediate) {
   if (immediate)
     timerfn();
   else
-    this._tmrKeepalive = setTimeout(timerfn, KEEPALIVE_INTERVAL);
+    this._tmrKeepalive = setTimeout(timerfn, interval);
 };
 
 Connection.prototype._login = function() {