Distributable cache for files

lib/response/file.js

@@ -7,12 +7,14 @@ var Mime = require('mime');
 var Err = require('../error');
 var Utils = require('../utils');
 var Stream = require('./stream');
+var LRU = require('lru-cache');
+var Crypto = require('crypto');
 
 
 // Declare internals
 
 var internals = {};
-
+internals.fileEtags = LRU();
 
 // File response  (Base -> Generic -> Stream -> File)
 
@@ -49,8 +51,23 @@ internals.File.prototype._prepare = function (request, callback) {
         Stream.call(self, stream);
         self._headers['Content-Type'] = Mime.lookup(self._filePath) || 'application/octet-stream';
         self._headers['Content-Length'] = stat.size;
-        self._headers['Last-Modified'] = new Date(stat.mtime).toUTCString();
-        self._headers.etag = JSON.stringify([stat.ino, stat.size, Date.parse(stat.mtime)].join('-'));
+
+        // Use stat info for an LRU cache key.
+        var cachekey = [self._filePath, stat.ino, stat.size, Date.parse(stat.mtime)].join('-');
+
+        // The etag must hash the file contents in order to be consistent between nodes.
+        if (internals.fileEtags.has(cachekey)) {
+            self._headers.etag = JSON.stringify(internals.fileEtags.get(cachekey));
+        } else {
+            var hash = Crypto.createHash('md5');
+            stream.on('data', function (chunk) {
+                hash.update(chunk);
+            })
+            stream.on('end', function () {
+                internals.fileEtags.set(cachekey, hash.digest("hex"));
+            })
+        }
+
         self._headers['Content-Disposition'] = 'inline; filename=' + encodeURIComponent(fileName);
 
         return Stream.prototype._prepare.call(self, request, callback);

package.json

@@ -37,7 +37,8 @@
     "catbox": "0.1.x",
     "cryptiles": "0.0.x",
     "iron": "0.1.x",
-    "semver": "1.1.0"
+    "semver": "1.1.0",
+    "lru-cache": "~2.2.2"
   },
   "devDependencies": {
     "mocha": "1.x.x",

test/integration/response.js

@@ -546,23 +546,6 @@ describe('Response', function () {
             });
         });
 
-        it('returns a 304 when the request has a future modifed-since', function (done) {
-
-            server.start(function () {
-
-                var date = new Date(Date.now());
-                var headers = {
-                    'if-modified-since': new Date(date.setFullYear(date.getFullYear() + 1)).toUTCString()
-                };
-
-                Request.get({ url: 'http://localhost:17082/file', headers: headers }, function (err, res) {
-
-                    expect(res.statusCode).to.equal(304);
-                    done();
-                });
-            });
-        });
-
         it('returns a gzipped file in the response when the request accepts gzip', function (done) {
 
             server.start(function () {