MDL-26028 send_file performance improvements

Includes X-Sendfile support, ETags for stored_files and general cleanup.

config-dist.php

@@ -220,6 +220,12 @@ $CFG->admin = 'admin';
 // about students being served outdated versions of uploaded files.
 //     $CFG->filelifetime = 86400;
 //
+// Some web servers can offload the file serving from PHP process,
+// comment out one the following options to enable it in Moodle:
+//     $CFG->xsendfile = 'X-Sendfile';           // Apache {@see https://tn123.org/mod_xsendfile/}
+//     $CFG->xsendfile = 'X-LIGHTTPD-send-file'; // Lighttpd {@see http://redmine.lighttpd.net/projects/lighttpd/wiki/X-LIGHTTPD-send-file}
+//     $CFG->xsendfile = 'X-Accel-Redirect';     // Nginx {@see http://wiki.nginx.org/XSendfile}
+//
 // This setting will prevent the 'My Courses' page being displayed when a student
 // logs in. The site front page will always show the same (logged-out) view.
 //     $CFG->disablemycourses = true;

lib/filestorage/file_storage.php

@@ -1294,6 +1294,22 @@ class file_storage {
         return array($contenthash, $filesize, $newfile);
     }
 
+    /**
+     * Serve file content using X-Sendfile header.
+     * Please make sure that all headers are already sent
+     * and the all access control checks passed.
+     *
+     * @param string $contenthash sah1 hash of the file content to be served
+     * @return bool success
+     */
+    public function xsendfile($contenthash) {
+        global $CFG;
+        require_once("$CFG->libdir/xsendfilelib.php");
+
+        $hashpath = $this->path_from_hash($contenthash);
+        return xsendfile("$hashpath/$contenthash");
+    }
+
     /**
      * Return path to file with given hash.
      *

lib/xsendfilelib.php

+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * X-Sendfile support
+ *
+ * @package   core_files
+ * @copyright 2012 Petr Skoda {@link http://skodak.org}
+ * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+//NOTE: do not verify MOODLE_INTERNAL here, this is used from themes too
+
+/**
+ * Serve file using X-Sendfile header, this needs special server module
+ * or configuration. Please make sure that all headers are already sent
+ * and the all access control checks passed.
+ *
+ * @param string $filepath
+ * @return bool success
+ */
+function xsendfile($filepath) {
+    global $CFG;
+
+    if (empty($CFG->xsendfile)) {
+        return false;
+    }
+
+    if (!file_exists($filepath)) {
+        return false;
+    }
+
+    if (headers_sent()) {
+        return false;
+    }
+
+    if ($CFG->xsendfile === 'X-LIGHTTPD-send-file') {
+        // http://redmine.lighttpd.net/projects/lighttpd/wiki/X-LIGHTTPD-send-file says 1.4 it does not support byteserving
+        header('Accept-Ranges: none');
+
+    } else if ($CFG->xsendfile === 'X-Accel-Redirect') {
+        // http://wiki.nginx.org/XSendfile
+        // Nginx is using relative path to protected folder, please note you can not use cache dir, tempdir and file pool outside of dataroot!
+        $filepath = realpath($filepath);
+        $dataroot = realpath($CFG->dataroot);
+        if (strpos($filepath, $dataroot) !== 0) {
+            return false;
+        }
+        $filepath = substr($filepath, strlen($dataroot));
+    }
+
+    header("$CFG->xsendfile: $filepath");
+
+    return true;
+}