https: reuse TLS sessions in Agent

Fix: #1499
PR-URL: https://github.com/nodejs/io.js/pull/2228
Reviewed-By: Shigeki Ohtsu <ohtsu@iij.ad.jp>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>

1 files changed, 49 insertions, 1 deletions

diff --git a/lib/https.js b/lib/https.js
index 21103b71af..abe4a20907 100644
--- a/lib/https.js
+++ b/lib/https.js
@@ -58,7 +58,25 @@ function createConnection(port, host, options) {
   }
 
   debug('createConnection', options);
-  return tls.connect(options);
+
+  if (options._agentKey) {
+    const session = this._getSession(options._agentKey);
+    if (session) {
+      debug('reuse session for %j', options._agentKey);
+      options = util._extend({
+        session: session
+      }, options);
+    }
+  }
+
+  const self = this;
+  const socket = tls.connect(options, function() {
+    if (!options._agentKey)
+      return;
+
+    self._cacheSession(options._agentKey, socket.getSession());
+  });
+  return socket;
 }
 
 
@@ -66,6 +84,14 @@ function Agent(options) {
   http.Agent.call(this, options);
   this.defaultPort = 443;
   this.protocol = 'https:';
+  this.maxCachedSessions = this.options.maxCachedSessions;
+  if (this.maxCachedSessions === undefined)
+    this.maxCachedSessions = 100;
+
+  this._sessionCache = {
+    map: {},
+    list: []
+  };
 }
 inherits(Agent, http.Agent);
 Agent.prototype.createConnection = createConnection;
@@ -100,6 +126,28 @@ Agent.prototype.getName = function(options) {
   return name;
 };
 
+Agent.prototype._getSession = function _getSession(key) {
+  return this._sessionCache.map[key];
+};
+
+Agent.prototype._cacheSession = function _cacheSession(key, session) {
+  // Fast case - update existing entry
+  if (this._sessionCache.map[key]) {
+    this._sessionCache.map[key] = session;
+    return;
+  }
+
+  // Put new entry
+  if (this._sessionCache.list.length >= this.maxCachedSessions) {
+    const oldKey = this._sessionCache.list.shift();
+    debug('evicting %j', oldKey);
+    delete this._sessionCache.map[oldKey];
+  }
+
+  this._sessionCache.list.push(key);
+  this._sessionCache.map[key] = session;
+};
+
 const globalAgent = new Agent();
 
 exports.globalAgent = globalAgent;