From 4af3d7e7a3402000b80df149de39e07473b89015 Mon Sep 17 00:00:00 2001
From: Sam Hemelryk <sam@moodle.com>
Date: Tue, 26 Feb 2013 16:35:45 +1300
Subject: [PATCH] MDL-38205 cache: implemented key prefix in memcache plugin

---
 cache/stores/memcache/lib.php | 41 ++++++++++++++++++++++++++---------
 1 file changed, 31 insertions(+), 10 deletions(-)

diff --git a/cache/stores/memcache/lib.php b/cache/stores/memcache/lib.php
index c457cc06e5c..906b3556e49 100644
--- a/cache/stores/memcache/lib.php
+++ b/cache/stores/memcache/lib.php
@@ -117,7 +117,7 @@ class cachestore_memcache extends cache_store implements cache_is_configurable {
             $this->connection->addServer($server[0], $server[1], true, $server[2]);
             // Test the connection to this server.
         }
-        $this->isready = @$this->connection->set("ping", 'ping', MEMCACHE_COMPRESSED, 1);
+        $this->isready = @$this->connection->set($this->parse_key('ping'), 'ping', MEMCACHE_COMPRESSED, 1);
     }
 
     /**
@@ -191,6 +191,20 @@ class cachestore_memcache extends cache_store implements cache_is_configurable {
         return self::MODE_APPLICATION + self::MODE_SESSION;
     }
 
+    /**
+     * Parses the given key to make it work for this memcache backend.
+     *
+     * @param string $key The raw key.
+     * @return string The resulting key.
+     */
+    protected function parse_key($key) {
+        if (strlen($key) > 245) {
+            $key = '_sha1_'.sha1($key);
+        }
+        $key = 'mdl_'.$key;
+        return $key;
+    }
+
     /**
      * Retrieves an item from the cache store given its key.
      *
@@ -198,7 +212,7 @@ class cachestore_memcache extends cache_store implements cache_is_configurable {
      * @return mixed The data that was associated with the key, or false if the key did not exist.
      */
     public function get($key) {
-        return $this->connection->get($key);
+        return $this->connection->get($this->parse_key($key));
     }
 
     /**
@@ -211,16 +225,23 @@ class cachestore_memcache extends cache_store implements cache_is_configurable {
      *      be set to false.
      */
     public function get_many($keys) {
-        $result = $this->connection->get($keys);
+        $mkeys = array();
+        foreach ($keys as $key) {
+            $mkeys[$key] = $this->parse_key($key);
+        }
+        $result = $this->connection->get($mkeys);
         if (!is_array($result)) {
             $result = array();
         }
-        foreach ($keys as $key) {
-            if (!array_key_exists($key, $result)) {
-                $result[$key] = false;
+        $return = array();
+        foreach ($mkeys as $key => $mkey) {
+            if (!array_key_exists($mkey, $result)) {
+                $return[$key] = false;
+            } else {
+                $return[$key] = $result[$mkey];
             }
         }
-        return $result;
+        return $return;
     }
 
     /**
@@ -231,7 +252,7 @@ class cachestore_memcache extends cache_store implements cache_is_configurable {
      * @return bool True if the operation was a success false otherwise.
      */
     public function set($key, $data) {
-        return $this->connection->set($key, $data, MEMCACHE_COMPRESSED, $this->definition->get_ttl());
+        return $this->connection->set($this->parse_key($key), $data, MEMCACHE_COMPRESSED, $this->definition->get_ttl());
     }
 
     /**
@@ -245,7 +266,7 @@ class cachestore_memcache extends cache_store implements cache_is_configurable {
     public function set_many(array $keyvaluearray) {
         $count = 0;
         foreach ($keyvaluearray as $pair) {
-            if ($this->connection->set($pair['key'], $pair['value'], MEMCACHE_COMPRESSED, $this->definition->get_ttl())) {
+            if ($this->connection->set($this->parse_key($pair['key']), $pair['value'], MEMCACHE_COMPRESSED, $this->definition->get_ttl())) {
                 $count++;
             }
         }
@@ -259,7 +280,7 @@ class cachestore_memcache extends cache_store implements cache_is_configurable {
      * @return bool Returns true if the operation was a success, false otherwise.
      */
     public function delete($key) {
-        return $this->connection->delete($key);
+        return $this->connection->delete($this->parse_key($key));
     }
 
     /**