From 7accdfa7dace92ac1a7df834d6ff2634d925d89c Mon Sep 17 00:00:00 2001
From: Petr Sloup <slouppetr@gmail.com>
Date: Wed, 27 Jul 2016 12:31:47 +0800
Subject: [PATCH] Very early CPU-cheap 304 based solely on last-modified

---
 src/serve_rendered.js | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/serve_rendered.js b/src/serve_rendered.js
index eb62a20..7492659 100644
--- a/src/serve_rendered.js
+++ b/src/serve_rendered.js
@@ -309,6 +309,13 @@ module.exports = function(options, repo, params, id) {
   };
 
   app.get(tilePattern, function(req, res, next) {
+    var modifiedSince = req.get('if-modified-since'), cc = req.get('cache-control');
+    if (modifiedSince && (!cc || cc.indexOf('no-cache') == -1)) {
+      if (new Date(lastModified) <= new Date(modifiedSince)) {
+        return res.sendStatus(304);
+      }
+    }
+
     var z = req.params.z | 0,
         x = req.params.x | 0,
         y = req.params.y | 0,