From 506fe169abcd603d6e0804e90b16c5c30b1ee20e Mon Sep 17 00:00:00 2001
From: Christian Klinger
Date: Wed, 8 Jun 2016 15:47:33 +0200
Subject: added a caching api proxy (that also validates the client IPs) for
 dozmod.

---
 modules-available/dozmod/api.inc.php | 84 +++++++++++++++++++++++++++++++++---
 1 file changed, 79 insertions(+), 5 deletions(-)

(limited to 'modules-available/dozmod')

diff --git a/modules-available/dozmod/api.inc.php b/modules-available/dozmod/api.inc.php
index f5525ef8..569b60a8 100644
--- a/modules-available/dozmod/api.inc.php
+++ b/modules-available/dozmod/api.inc.php
@@ -1,11 +1,64 @@
 <?php 
-/* Hier kommt der Dozmod proxy hin */
+/* small API server that acts as a proxy to the dozmod server.
+ * To reduce the number of requests and connections to dozmod-server, results
+ * gets cached into a file cache.
+ *
+ * Required Configuration:
+ * CONFIG_DOZMOD_EXPIRE: Expiration time in seconds for the cache
+ * CONFIG_DOZMOD: URL to the dozmod server
+ * 
+ **/
+
 require 'modules/locations/inc/location.inc.php';
 
+
 define('LIST_URL', CONFIG_DOZMOD . '/vmchooser/list');
 define('VMX_URL', CONFIG_DOZMOD . '/vmchooser/lecture');
 $availableRessources = ['vmx', 'test', 'netrules'];
 
+/* BEGIN: A simple caching mechanism ---------------------------- */
+
+function cache_hash($obj) {
+    return md5(serialize($obj)); 
+}
+
+function cache_key_to_filename($key) {
+    return "/tmp/bwlp-slxadmin-cache-$key"; // TODO: hash
+}
+
+function cache_put($key, $value) {
+    $filename = cache_key_to_filename($key);
+    file_put_contents($filename, $value);
+}
+
+function cache_has($key) {
+    $filename = cache_key_to_filename($key);
+    $mtime = filemtime($filename);
+
+    if (!$mtime) {
+        return false; // cache miss
+    }
+    if ( time() - $mtime  > CONFIG_DOZMOD_EXPIRE) {
+        return false;
+    } else {
+        return true;
+    }
+}
+
+
+function cache_get($key) {
+    $filename = cache_key_to_filename($key);
+    return file_get_contents($filename); 
+}
+
+/* good for large binary files */
+function cache_get_passthru($key) {
+    $filename = cache_key_to_filename($key);
+    $fp = fopen($filename, "r");
+    fpassthru($fp);
+}
+/* END: Cache ---------------------------------------------------- */
+
 
 /* this script requires 2 (3 with implicit client ip) parameters 
  *
@@ -18,9 +71,8 @@ function println($str) { echo "$str\n"; }
 
 /* return an array of lecutre uuids.
  * Parameter: an array with location Ids
- * Cacheable
  * */
-function getLecturesForLocations($locationIds) {
+function _getLecturesForLocations($locationIds) {
     $ids = implode('%20', $locationIds);
     $url = LIST_URL . "?locations=$ids";
     $responseXML = Download::asString($url, 60, $code);
@@ -32,13 +84,36 @@ function getLecturesForLocations($locationIds) {
     }
     return $uuids;
 } 
+/** Caching wrapper around _getLecturesForLocations() *//
+function getLecturesForLocations($locationIds) {
+    $key = 'lectures_' . cache_hash($locationIds);
+    if (cache_has($key)) {
+        return unserialize(cache_get($key));
+    } else {
+        $value = _getLecturesForLocations($locationIds);
+        cache_put($key, serialize($value));
+        return $value;
+    }
+}
 
-function getVMX($lecture_uuid) {
+function _getVMX($lecture_uuid) {
     $url = VMX_URL . '/' . $lecture_uuid;
     $response = Download::asString($url, 60, $code);
     return $response;
 }
 
+/** Caching wrapper around _getVMX() **/
+function getVMX($lecture_uuid) {
+    $key = 'vmx_' . $lecture_uuid;
+    if (cache_has($key)) {
+        cache_get_passthru($key);
+    } else {
+        $value = _getVMX($lecture_uuid);
+        cache_put($key, $value);
+        return $value;
+    }
+}
+
 
 // -----------------------------------------------------------------------------// 
 $ip = $_SERVER['REMOTE_ADDR'];
@@ -58,7 +133,6 @@ $location_ids = Location::getFromIP($request['ip']);
 /* lookup lecture uuids */
 $lectures = getLecturesForLocations(array($location_ids));
 
-
 /* validate request -------------------------------------------- */
 /* check ressources */
 if (!in_array($request['ressource'], $availableRessources)) {
-- 
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