objectcache: make BagOStuff::changeTTL() more atomic

Change-Id: I86493498ef3359046b12d51795cf7875af6c3a6c

diff --git a/includes/libs/objectcache/BagOStuff.php b/includes/libs/objectcache/BagOStuff.php
index 27c6167..e2b0212 100644 (file)
--- a/includes/libs/objectcache/BagOStuff.php
+++ b/includes/libs/objectcache/BagOStuff.php
@@ -139,7 +139,7 @@ abstract class BagOStuff implements IExpiringStore, LoggerAwareInterface {
        /**
         * Get an item with the given key, regenerating and setting it if not found
         *
-        * If the callback returns false, then nothing is stored.
+        * Nothing is stored nor deleted if the callback returns false
         *
         * @param string $key
         * @param int $ttl Time-to-live (seconds)
@@ -176,7 +176,7 @@ abstract class BagOStuff implements IExpiringStore, LoggerAwareInterface {
         * @param string $key
         * @param int $flags Bitfield of BagOStuff::READ_* constants [optional]
         * @param int|null $oldFlags [unused]
-        * @return mixed Returns false on failure and if the item does not exist
+        * @return mixed Returns false on failure or if the item does not exist
         */
        public function get( $key, $flags = 0, $oldFlags = null ) {
                // B/C for ( $key, &$casToken = null, $flags = 0 )
@@ -223,7 +223,7 @@ abstract class BagOStuff implements IExpiringStore, LoggerAwareInterface {
        /**
         * @param string $key
         * @param int $flags Bitfield of BagOStuff::READ_* constants [optional]
-        * @return mixed Returns false on failure and if the item does not exist
+        * @return mixed Returns false on failure or if the item does not exist
         */
        abstract protected function doGet( $key, $flags = 0 );
 
@@ -233,7 +233,7 @@ abstract class BagOStuff implements IExpiringStore, LoggerAwareInterface {
         * @param string $key
         * @param mixed &$casToken
         * @param int $flags Bitfield of BagOStuff::READ_* constants [optional]
-        * @return mixed Returns false on failure and if the item does not exist
+        * @return mixed Returns false on failure or if the item does not exist
         * @throws Exception
         */
        protected function getWithToken( $key, &$casToken, $flags = 0 ) {
@@ -267,7 +267,7 @@ abstract class BagOStuff implements IExpiringStore, LoggerAwareInterface {
         * (which will be false if not present), and takes the arguments:
         * (this BagOStuff, cache key, current value, TTL).
         * The TTL parameter is reference set to $exptime. It can be overriden in the callback.
-        * If the callback returns false, then the current value will be unchanged (including TTL).
+        * Nothing is stored nor deleted if the callback returns false.
         *
         * @param string $key
         * @param callable $callback Callback method to be executed
@@ -422,18 +422,32 @@ abstract class BagOStuff implements IExpiringStore, LoggerAwareInterface {
        }
 
        /**
-        * Reset the TTL on a key if it exists
+        * Change the expiration on a key if it exists
+        *
+        * If an expiry in the past is given then the key will immediately be expired
         *
         * @param string $key
-        * @param int $expiry
+        * @param int $expiry TTL or UNIX timestamp
         * @param int $flags Bitfield of BagOStuff::WRITE_* constants (since 1.33)
-        * @return bool Success Returns false if there is no key
+        * @return bool Success Returns false on failure or if the item does not exist
         * @since 1.28
         */
        public function changeTTL( $key, $expiry = 0, $flags = 0 ) {
-               $value = $this->get( $key );
+               $found = false;
+
+               $ok = $this->merge(
+                       $key,
+                       function ( $cache, $ttl, $currentValue ) use ( &$found ) {
+                               $found = ( $currentValue !== false );
+
+                               return $currentValue; // nothing is written if this is false
+                       },
+                       $expiry,
+                       1, // 1 attempt
+                       $flags
+               );
 
-               return ( $value === false ) ? false : $this->set( $key, $value, $expiry, $flags );
+               return ( $ok && $found );
        }
 
        /**