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https://github.com/EGroupware/egroupware.git
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store some lock-data, so only a single callback calculate data on cache-miss
done to avoid race-conditions where many processes try to fetch and therefore calculate some expensive to calculate data eg. mass-mailings in our hosting
This commit is contained in:
Ralf Becker
parent
691fb06de5
commit
cda95d8188
@ -28,10 +28,10 @@ namespace EGroupware\Api;
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* getXXX($app,$location,$callback=null,array $callback_params,$expiration=0)
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* has three optional parameters allowing to specify:
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* 3. a callback if requested data is not yes stored. In that case the callback is called
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* and it's value is stored in the cache AND retured
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* and it's value is stored in the cache AND returned
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* 4. parameters to pass to the callback as array, see call_user_func_array
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* 5. an expiration time in seconds to specify how long data should be cached,
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* default 0 means infinit (this time is not supported for request level!)
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* default 0 means infinite (this time is not supported for request level!)
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*
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* Data is stored under an application name and a location, like egw_session::appsession().
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* In fact data stored at cache level Api\Cache::SESSION, is stored in the same way as
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@ -42,14 +42,23 @@ namespace EGroupware\Api;
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* The tree and instance wide cache uses a certain provider class, to store the data
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* eg. in memcached or if there's nothing else configured in the filesystem (eGW's temp_dir).
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*
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* "Admin >> clear cache and register hooks" allways only clears instance level cache of
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* "Admin >> clear cache and register hooks" always only clears instance level cache of
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* calling instance. It never clears tree level cache, which makes it important to set
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* resonable expiry times or think about an other means of clearing that particular item.
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* reasonable expiry times or think about an other means of clearing that particular item.
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* (Not clearing of tree-level cache is important, as regenerating it is an expensive
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* operation for a huge scale EGroupware hosting operation.)
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*
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* Apps needing to talk to multiple EGroupware instances (eg. Stylite Managementserver)
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* Apps needing to talk to multiple EGroupware instances (eg. EGroupware Managementserver)
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* can use install_id of instance as $level parameter to (set|get|unset)Cache method.
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*
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* If a callback is used to calculate the data, in case it's not found in the cache, e.g.:
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* $data = Api\Cache::getCache(Api\Cache::(TREE|INSTANCE), $app, $location, function($params)
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* {
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* // code to calculate / query $data
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* return $data;
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* }, $params, $expiration);
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* then we lock the $app:$location by storing some specific data, so only one callback is used
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* to calculate the data, and other processes sleep until the data is calculate to avoid races.
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*/
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class Cache
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{
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@ -108,7 +117,7 @@ class Cache
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* @param int $expiration =0 expiration time in seconds, default 0 = never
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* @return boolean true if data could be stored, false otherwise incl. key already existed
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*/
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static public function addCache($level,$app,$location,$data,$expiration=0)
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public static function addCache($level,$app,$location,$data,$expiration=0)
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{
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//error_log(__METHOD__."('$level','$app','$location',".array2string($data).",$expiration)");
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switch($level)
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@ -144,7 +153,7 @@ class Cache
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* @param int $expiration =0 expiration time in seconds, default 0 = never
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* @return boolean true if data could be stored, false otherwise
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*/
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static public function setCache($level,$app,$location,$data,$expiration=0)
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public static function setCache($level,$app,$location,$data,$expiration=0)
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{
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//error_log(__METHOD__."('$level','$app','$location',".array2string($data).",$expiration)");
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switch($level)
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@ -170,6 +179,19 @@ class Cache
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throw new Exception\WrongParameter(__METHOD__."() unknown level '$level'!");
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}
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/**
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* Content stored to signal one callback is already running and calculating the data, to not run it multiple times
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*/
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const CALLBACK_LOCK = '***LOCKED***';
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/**
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* Maximum time an item is locked, to recover from eg. a crash while the lock is set
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*/
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const CALLBACL_LOCK_TIMEOUT = 10; // 10s
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/**
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* Time other processes sleep to wait for one callback to calculate the data
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*/
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const CALLBACK_LOCK_USLEEP = 50000; // 50ms
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/**
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* Get some data from the cache
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*
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@ -182,7 +204,7 @@ class Cache
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* @return mixed NULL if data not found in cache (and no callback specified) or
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* if $location is an array: location => data pairs for existing location-data, non-existing is not returned
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*/
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static public function getCache($level,$app,$location,$callback=null,array $callback_params=array(),$expiration=0)
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public static function getCache($level,$app,$location,$callback=null,array $callback_params=array(),$expiration=0)
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{
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switch($level)
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{
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@ -224,16 +246,39 @@ class Cache
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}
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else
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{
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$data = $provider->get($keys=self::keys($level,$app,$location));
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if (is_null($data) && !is_null($callback))
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// try reading cached data and, if not found AND a callback to do so given, calculate it
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// only allow one process to do the (heavy) calculation by storing some lock-data
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// other processes reading the lock-data sleep for a short time, before try reading it again
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for($n=10+self::CALLBACL_LOCK_TIMEOUT*1000000/self::CALLBACK_LOCK_USLEEP; $n >= 0; $n--)
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{
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$data = call_user_func_array($callback,$callback_params);
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// limit expiration to configured maximum time
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if (isset(self::$max_expiration) && (!$expiration || $expiration > self::$max_expiration))
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$data = $provider->get($keys=self::keys($level,$app,$location));
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if ($data === self::CALLBACK_LOCK)
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{
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$expiration = self::$max_expiration;
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usleep(self::CALLBACK_LOCK_USLEEP);
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}
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elseif($data === null && isset($callback))
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{
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$provider->set($keys, self::CALLBACK_LOCK, self::CALLBACL_LOCK_TIMEOUT);
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try {
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$data = call_user_func_array($callback, $callback_params);
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}
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catch(\Throwable $e) {
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// remove lock, before re-throwing the exception/error
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$provider->delete($keys);
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throw $e;
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}
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// limit expiration to configured maximum time
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if (isset(self::$max_expiration) && (!$expiration || $expiration > self::$max_expiration))
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{
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$expiration = self::$max_expiration;
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}
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$provider->set($keys, $data, $expiration);
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break;
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}
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else
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{
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break;
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}
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$provider->set($keys,$data,$expiration);
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}
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}
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}
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@ -254,7 +299,7 @@ class Cache
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* @param string $location location name for data
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* @return boolean true if data was set, false if not (like isset())
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*/
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static public function unsetCache($level,$app,$location)
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public static function unsetCache($level,$app,$location)
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{
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switch($level)
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{
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@ -283,7 +328,7 @@ class Cache
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* @param int $expiration =0 expiration time in seconds, default 0 = never
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* @return boolean true if data could be stored, false otherwise
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*/
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static public function setTree($app,$location,$data,$expiration=0)
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public static function setTree($app,$location,$data,$expiration=0)
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{
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//error_log(__METHOD__."('$app','$location',".array2string($data).",$expiration)");
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return self::setCache(self::TREE,$app,$location,$data,$expiration);
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@ -299,7 +344,7 @@ class Cache
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* @param int $expiration =0 expiration time in seconds, default 0 = never
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* @return mixed NULL if data not found in cache (and no callback specified)
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*/
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static public function getTree($app,$location,$callback=null,array $callback_params=array(),$expiration=0)
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public static function getTree($app,$location,$callback=null,array $callback_params=array(),$expiration=0)
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{
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return self::getCache(self::TREE,$app,$location,$callback,$callback_params,$expiration);
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}
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@ -311,7 +356,7 @@ class Cache
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* @param string $location location name for data
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* @return boolean true if data was set, false if not (like isset())
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*/
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static public function unsetTree($app,$location)
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public static function unsetTree($app,$location)
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{
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return self::unsetCache(self::TREE,$app,$location);
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}
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@ -325,7 +370,7 @@ class Cache
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* @param int $expiration =0 expiration time in seconds, default 0 = never
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* @return boolean true if data could be stored, false otherwise
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*/
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static public function setInstance($app,$location,$data,$expiration=0)
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public static function setInstance($app,$location,$data,$expiration=0)
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{
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return self::setCache(self::INSTANCE,$app,$location,$data,$expiration);
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}
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@ -340,7 +385,7 @@ class Cache
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* @param int $expiration =0 expiration time in seconds, default 0 = never
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* @return mixed NULL if data not found in cache (and no callback specified)
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*/
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static public function getInstance($app,$location,$callback=null,array $callback_params=array(),$expiration=0)
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public static function getInstance($app,$location,$callback=null,array $callback_params=array(),$expiration=0)
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{
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return self::getCache(self::INSTANCE,$app,$location,$callback,$callback_params,$expiration);
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}
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@ -352,7 +397,7 @@ class Cache
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* @param string $location location name for data
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* @return boolean true if data was set, false if not (like isset())
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*/
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static public function unsetInstance($app,$location)
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public static function unsetInstance($app,$location)
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{
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return self::unsetCache(self::INSTANCE,$app,$location);
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}
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@ -371,7 +416,7 @@ class Cache
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* @param int $expiration =0 expiration time in seconds, default 0 = never
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* @return boolean true if data could be stored, false otherwise
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*/
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static public function setSession($app,$location,$data,$expiration=0)
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public static function setSession($app,$location,$data,$expiration=0)
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{
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if (isset($_SESSION[Session::EGW_SESSION_ENCRYPTED]))
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{
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@ -400,7 +445,7 @@ class Cache
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* @param int $expiration =0 expiration time in seconds, default 0 = never
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* @return mixed NULL if data not found in cache (and no callback specified)
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*/
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static public function &getSession($app,$location,$callback=null,array $callback_params=array(),$expiration=0)
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public static function &getSession($app, $location, $callback=null, array $callback_params=array(), $expiration=0)
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{
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if (isset($_SESSION[Session::EGW_SESSION_ENCRYPTED]))
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{
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@ -429,7 +474,7 @@ class Cache
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* @param string $location location name for data
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* @return boolean true if data was set, false if not (like isset())
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*/
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static public function unsetSession($app,$location)
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public static function unsetSession($app,$location)
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{
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if (isset($_SESSION[Session::EGW_SESSION_ENCRYPTED]))
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{
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@ -468,7 +513,7 @@ class Cache
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* @param int $expiration =0 expiration time is NOT used for REQUEST!
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* @return boolean true if data could be stored, false otherwise
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*/
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static public function setRequest($app,$location,$data,$expiration=0)
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public static function setRequest($app,$location,$data,$expiration=0)
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{
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unset($expiration); // not used, but required by function signature
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self::$request_cache[$app][$location] = $data;
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@ -486,7 +531,7 @@ class Cache
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* @param int $expiration =0 expiration time is NOT used for REQUEST!
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* @return mixed NULL if data not found in cache (and no callback specified)
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*/
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static public function getRequest($app,$location,$callback=null,array $callback_params=array(),$expiration=0)
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public static function getRequest($app,$location,$callback=null,array $callback_params=array(),$expiration=0)
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{
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unset($expiration); // not used, but required by function signature
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if (!isset(self::$request_cache[$app][$location]) && !is_null($callback))
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@ -503,7 +548,7 @@ class Cache
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* @param string $location location name for data
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* @return boolean true if data was set, false if not (like isset())
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*/
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static public function unsetRequest($app,$location)
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public static function unsetRequest($app,$location)
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{
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if (!isset(self::$request_cache[$app][$location]))
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{
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@ -521,7 +566,7 @@ class Cache
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*
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* @param string $level Api\Cache::(TREE|INSTANCE) or install_id
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* @param boolean $log_not_found =true false do not log if no provider found, used eg. to supress error via unsetCache during installation
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* @return Api\Cache\Provider
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* @return Cache\Provider|Cache\ProviderMultiple
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*/
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static protected function get_provider($level, $log_not_found=true)
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{
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@ -602,7 +647,7 @@ class Cache
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* @param boolean $throw =true throw an exception, if we can't retriev the value
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* @return string|boolean string with config or false if not found and !$throw
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*/
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static public function get_system_config($name,$throw=true)
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public static function get_system_config($name, $throw=true)
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{
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if(!isset($GLOBALS['egw_info']['server'][$name]))
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{
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@ -642,7 +687,7 @@ class Cache
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* @param string $level =self::INSTANCE
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* @param string $app =null app-name or "all" to empty complete cache
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*/
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static public function flush($level=self::INSTANCE, $app=null)
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public static function flush($level=self::INSTANCE, $app=null)
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{
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$ret = true;
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if (!($provider = self::get_provider($level)))
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@ -670,7 +715,7 @@ class Cache
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/**
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* Unset instance key, so it get read again and re-read install_id from database
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*/
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static public function unset_instance_key()
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public static function unset_instance_key()
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{
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self::$instance_key = null;
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$GLOBALS['egw_info']['server']['install_id'] = self::get_system_config('install_id', false);
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@ -689,7 +734,7 @@ class Cache
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* @param string $install_id =null default use install_id of current instance
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* @return string new key also stored in self::$instance_key
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*/
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static public function generate_instance_key($install_id=null)
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public static function generate_instance_key($install_id=null)
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{
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if (!isset($install_id))
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{
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@ -711,7 +756,7 @@ class Cache
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* @param string $location =null
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* @return array
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*/
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static public function keys($level, $app=null, $location=null)
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public static function keys($level, $app=null, $location=null)
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{
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static $tree_key = null;
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@ -16,7 +16,7 @@ namespace EGroupware\Api\Cache;
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/**
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* Interface for a caching provider being able to retrieve multiple entires
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*/
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interface ProviderMultiple
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interface ProviderMultiple extends Provider
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{
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/**
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* Get multiple data from the cache
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