Implemented reades-writer-lock for updating the cached rrd images. Th…

…is should make updating the graphs much more robust on well frequented sites.

graph.php

@@ -2,7 +2,7 @@
 /**
  * RRDGraph Plugin: Graph generator
  * 
- * @author Daniel Goß <[email protected]>
+ * @author Daniel Go� <[email protected]>
  * @license MIT
  */
 
@@ -30,7 +30,7 @@
     //-- ACL-Check
     if (auth_quickaclcheck($pageId) < AUTH_READ) throw new Exception("Access denied by ACL.");
 
-    //-- Currently only fs and e are supported moeds.
+    //-- Currently only fs and e are supported modes.
     if ($mode != 'fs') $mode = 'e';
 
     //-- Load the rrdgraph helper. This helper contains the cache manager and other stuff used here.
@@ -41,6 +41,10 @@
     $cacheInfo = $rrdGraphHelper->getImageCacheInfo($pageId, $graphId, $rangeNr, $mode);
     if (! $cacheInfo->isValid()) {
 
+        //-- We found we should update the file. Upgrade our lock to an exclusive one.
+        //   This way we OWN the lockfile and nobody else can get confused while we do our thing.
+        $cacheInfo->upgradeLock();
+
         $recipe = $rrdGraphHelper->fetchRecipe($pageId, $graphId);
         if ($recipe === null) throw new Exception("The graph " . $graphId . " is not defined on page " . $pageId);
 
@@ -137,12 +141,17 @@
         }
 
         //-- Correct the filename of the graph in case the rangeNr was modified by the range check.
+        unset($cacheInfo);
         $cacheInfo = $rrdGraphHelper->getImageCacheInfo($pageId, $graphId, $rangeNr, $mode);
 
+        //-- We've to reupgrade the lock, because we got a new cacheInfo instance.
+        $cacheInfo->UpgradeLock();
+
         //-- Render the RRD-Graph
-        if (rrd_graph($cacheInfo->getFilename(), array_merge($commandLine, $graphCommands)) === false) {throw new Exception(rrd_error());}
+        if (rrd_graph($cacheInfo->getFilename(), array_merge($commandLine, $graphCommands)) === false) throw new Exception(rrd_error());
 
         //-- Get the new cache info of the image to send the correct headers.
+        unset($cacheInfo);
         $cacheInfo = $rrdGraphHelper->getImageCacheInfo($pageId, $graphId, $rangeNr, $mode);
     }
 
@@ -165,3 +174,5 @@
 catch (Exception $ex) {
     ErrorImage::outputErrorImage("Graph generation failed", $ex->getMessage());
 }
+
+if (isset($cacheInfo)) unset($cacheInfo);

helper.php

@@ -2,7 +2,7 @@
 /**
  * RRDGraph Plugin: Helper classes
  * 
- * @author Daniel Goß <[email protected]>
+ * @author Daniel Go� <[email protected]>
  * @license MIT
  */
 
@@ -158,6 +158,9 @@ public function getLastModified() {
 class rrdgraph_image_info {
 	/** @var String Name of the rrd image file within the cache. */
     private $fileName;
+
+    /** @var Resource File handle used to lock the file. */
+    private $fileHandle;
 
     /** @var Integer Timestamp until the file named by $fileName ist considered valid. */
     private $validUntil;
@@ -175,6 +178,17 @@ public function __construct($fileName, $validUntil, $lastModified) {
         $this->fileName = $fileName;
         $this->validUntil = $validUntil;
         $this->lastModified = $lastModified;
+
+        //-- Get a shared lock on the lock-file.
+        $this->fileHandle = fopen($fileName . ".lock", "w+");
+        flock($this->fileHandle, LOCK_SH);
+    }
+
+    /**
+     * D'tor
+     */
+    public function __destruct() {
+        fclose($this->fileHandle);
     }
 
     /**
@@ -205,6 +219,10 @@ public function getLastModified() {
     public function isValid() {
         return $this->validUntil > time();
     }
+
+    public function upgradeLock() {
+        flock($this->fileHandle, LOCK_EX);
+    }
 }
 
 /**

plugin.info.txt

@@ -1,7 +1,7 @@
 base   rrdgraph
 author Daniel Goß
 email  [email protected]
-date   2014-10-20
+date   2015-04-04
 name   RRD graph generator
 desc   This plugin creates graphs from RRD tool data. Uses php5-rrd to generate the images.
-url    http://www.tobedone.info/
+url    https://github.com/FlashSystems/rrdgraph