inc/AwlCache.php

   1 <?php
   2
   3 /**
   4  * A simple Memcached wrapper supporting namespacing of stored values.
   5  *
   6  * @author Andrew McMillan
   7  * @license LGPL v2 or later
   8  */
   9
  10 class AwlCache {
  11   private static $m;
  12   private static $servers;
  13   private static $working;
  14
  15   /**
  16    * Initialise the cache connection. We use getpid() to give us a persistent connection.
  17    */
  18   function __construct() {
  19     global $c;
  20
  21     if ( isset(self::$working) ) return;
  22
  23     self::$working = false;
  24     if ( isset($c->memcache_servers) && class_exists('Memcached') ) {
  25       dbg_error_log('Cache', 'Using Memcached interface connection');
  26       self::$servers = $c->memcache_servers;
  27       self::$m = new Memcached();
  28       foreach( self::$servers AS $v ) {
  29         dbg_error_log('Cache', 'Adding server '.$v);
  30         $server = explode(',',$v);
  31         if ( isset($server[2]) )
  32           self::$m->addServer($server[0],$server[1],$server[2]);
  33         else
  34           self::$m->addServer($server[0],$server[1]);
  35       }
  36       self::$working = true;
  37       // Hack to allow the regression tests to flush the cache at start
  38       if ( isset($_SERVER['HTTP_X_DAVICAL_FLUSH_CACHE'])) $this->flush();
  39     }
  40     else {
  41       dbg_error_log('Cache', 'Using NoCache dummy interface');
  42     }
  43   }
  44
  45   /**
  46    * So we can find out if we are actually using the cache.
  47    */
  48   function isActive() {
  49     return self::$working;
  50   }
  51
  52   /**
  53    * Construct a string from the namespace & key
  54    * @param unknown_type $namespace
  55    * @param unknown_type $key
  56    */
  57   private function nskey( $namespace, $key ) {
  58     return str_replace(' ', '%20', $namespace . (isset($key) ? '~~' . $key: '')); // for now.
  59   }
  60
  61   /**
  62    * get a value from the specified namespace / key
  63    * @param $namespace
  64    * @param $key
  65    */
  66   function get( $namespace, $key ) {
  67     if ( !self::$working ) return false;
  68     $ourkey = self::nskey($namespace,$key);
  69     $value = self::$m->get($ourkey);
  70 //    var_dump($value);
  71 //    if ( $value !== false ) dbg_error_log('Cache', 'Got value for cache key "'.$ourkey.'" - '.strlen(serialize($value)).' bytes');
  72     return $value;
  73   }
  74
  75   /**
  76    * Set a value for the specified namespace/key, perhaps with an expiry (default 10 days)
  77    * @param $namespace
  78    * @param $key
  79    * @param $value
  80    * @param $expiry
  81    */
  82   function set( $namespace, $key, $value, $expiry=864000 ) {
  83     if ( !self::$working ) return false;
  84     $ourkey = self::nskey($namespace,$key);
  85     $nskey = self::nskey($namespace,null);
  86     $keylist = self::$m->get( $nskey, null, $cas_token );
  87     if ( isset($keylist) && is_array($keylist) ) {
  88       if ( !isset($keylist[$ourkey]) ) {
  89         $keylist[$ourkey] = 1;
  90         $success = self::$m->cas( $cas_token, $nskey, $keylist );
  91         $i=0;
  92         while( !$success && $i++ < 10 && self::$m->getResultCode() == Memcached::RES_DATA_EXISTS ) {
  93           $keylist = self::$m->get( $nskey, null, $cas_token );
  94           if ( $keylist === false ) return false;
  95           if ( isset($keylist[$ourkey]) ) break;
  96           $keylist[$ourkey] = 1;
  97           $success = self::$m->cas( $cas_token, $nskey, $keylist );
  98         }
  99         if ( !$success ) return false;
 100       }
 101     }
 102     else {
 103       $keylist = array( $ourkey => 1 );
 104       self::$m->set( $nskey, $keylist );
 105     }
 106 //    var_dump($value);
 107 //    dbg_error_log('Cache', 'Setting value for cache key "'.$ourkey.'" - '.strlen(serialize($value)).' bytes');
 108     return self::$m->set( $ourkey, $value, $expiry );
 109   }
 110
 111   /**
 112    * Delete a value from a namespace/key, or for everything in a namespace if a 'null' key is supplied.
 113    * @param $namespace
 114    * @param $key
 115    */
 116   function delete( $namespace, $key ) {
 117     if ( !self::$working ) return false;
 118     $nskey = self::nskey($namespace,$key);
 119     dbg_error_log('Cache', 'Deleting from cache key "'.$nskey.'"');
 120     if ( isset($key) ) {
 121       self::$m->delete( $nskey );
 122     }
 123     else {
 124       $keylist = self::$m->get( $nskey, null, $cas_token );
 125       if ( isset($keylist) ) {
 126       self::$m->delete( $nskey );
 127         if ( is_array($keylist) ) {
 128           foreach( $keylist AS $k => $v ) self::$m->delete( $k );
 129         }
 130       }
 131     }
 132   }
 133
 134   /**
 135    * Flush the entire cache
 136    */
 137   function flush( ) {
 138     if ( !self::$working ) return false;
 139     dbg_error_log('Cache', 'Flushing cache');
 140     self::$m->flush();
 141   }
 142 }
 143
 144
 145 function getCacheInstance() {
 146   static $ourCacheInstance;
 147
 148   if ( !isset($ourCacheInstance) ) $ourCacheInstance = new AWLCache('Memcached');
 149
 150   return $ourCacheInstance;
 151 }