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<?php
/**
* File: Cache_Memcache.php
*
* @package W3TC
*/
namespace W3TC;
/**
* Class Cache_Memcache
*
* PECL Memcache class
* Older than Memcached
*
* phpcs:disable PSR2.Classes.PropertyDeclaration.Underscore
* phpcs:disable PSR2.Methods.MethodDeclaration.Underscore
* phpcs:disable WordPress.PHP.NoSilencedErrors.Discouraged
* phpcs:disable Universal.CodeAnalysis.ConstructorDestructorReturn.ReturnValueFound
*/
class Cache_Memcache extends Cache_Base {
/**
* Memcache object
*
* @var Memcache
*/
private $_memcache = null;
/**
* Used for faster flushing
*
* @var integer $_key_version
*/
private $_key_version = array();
/**
* Cache_Memcache constructor.
*
* Initializes the Memcache connection and sets up servers based on the provided configuration.
*
* @param array $config {
* Configuration for Memcache, including.
*
* @type array $servers List of Memcache server endpoints.
* @type bool $persistent Whether to use persistent connections.
* @type string $key_version_mode Mode for key versioning ('disabled' to disable it).
* }
*/
public function __construct( $config ) {
parent::__construct( $config );
$this->_memcache = new \Memcache();
if ( ! empty( $config['servers'] ) ) {
$persistent = isset( $config['persistent'] ) ? (bool) $config['persistent'] : false;
foreach ( (array) $config['servers'] as $server ) {
list( $ip, $port ) = Util_Content::endpoint_to_host_port( $server );
$this->_memcache->addServer( $ip, $port, $persistent );
}
} else {
return false;
}
// when disabled - no extra requests are made to obtain key version, but flush operations not supported as a result
// group should be always empty.
if ( isset( $config['key_version_mode'] ) && 'disabled' === $config['key_version_mode'] ) {
$this->_key_version[''] = 1;
}
return true;
}
/**
* Adds a new value to the cache.
*
* If the key already exists, it will overwrite the value. This method is functionally equivalent to `set()`.
*
* @param string $key Cache key.
* @param mixed $value Value to store.
* @param int $expire Time to live for the cached item in seconds. Default is 0 (no expiration).
* @param string $group Cache group. Default is an empty string.
*
* @return bool True on success, false on failure.
*/
public function add( $key, &$value, $expire = 0, $group = '' ) {
return $this->set( $key, $value, $expire, $group );
}
/**
* Sets a value in the cache.
*
* This method stores the value in Memcache with a specific key, expiration time, and group. It also includes a versioning
* mechanism to handle key updates.
*
* @param string $key Cache key.
* @param mixed $value Value to store.
* @param int $expire Time to live for the cached item in seconds. Default is 0 (no expiration).
* @param string $group Cache group. Default is an empty string.
*
* @return bool True on success, false on failure.
*/
public function set( $key, $value, $expire = 0, $group = '' ) {
if ( ! isset( $value['key_version'] ) ) {
$value['key_version'] = $this->_get_key_version( $group );
}
$storage_key = $this->get_item_key( $key );
return @$this->_memcache->set( $storage_key, $value, false, $expire );
}
/**
* Retrieves a value and its old version from the cache.
*
* This method fetches the cached value for the given key. If the key version does not match the current version, it may return
* expired data based on configuration.
*
* @param string $key Cache key.
* @param string $group Cache group. Default is an empty string.
*
* @return array Array containing the value (or null) and a boolean indicating if old data was returned.
*/
public function get_with_old( $key, $group = '' ) {
$has_old_data = false;
$storage_key = $this->get_item_key( $key );
$v = @$this->_memcache->get( $storage_key );
if ( ! is_array( $v ) || ! isset( $v['key_version'] ) ) {
return array( null, $has_old_data );
}
$key_version = $this->_get_key_version( $group );
if ( $v['key_version'] === $key_version ) {
return array( $v, $has_old_data );
}
if ( $v['key_version'] > $key_version ) {
if ( ! empty( $v['key_version_at_creation'] ) && $v['key_version_at_creation'] !== $key_version ) {
$this->_set_key_version( $v['key_version'], $group );
}
return array( $v, $has_old_data );
}
// key version is old.
if ( ! $this->_use_expired_data ) {
return array( null, $has_old_data );
}
// if we have expired data - update it for future use and let current process recalculate it.
$expires_at = isset( $v['expires_at'] ) ? $v['expires_at'] : null;
if ( null === $expires_at || time() > $expires_at ) {
$v['expires_at'] = time() + 30;
@$this->_memcache->set( $storage_key, $v, false, 0 );
$has_old_data = true;
return array( null, $has_old_data );
}
// return old version.
return array( $v, $has_old_data );
}
/**
* Replaces the value for an existing key in the cache.
*
* This method is functionally equivalent to `set()`.
*
* @param string $key Cache key.
* @param mixed $value Value to store.
* @param int $expire Time to live for the cached item in seconds. Default is 0 (no expiration).
* @param string $group Cache group. Default is an empty string.
*
* @return bool True on success, false on failure.
*/
public function replace( $key, &$value, $expire = 0, $group = '' ) {
return $this->set( $key, $value, $expire, $group );
}
/**
* Deletes a value from the cache.
*
* If expired data is allowed, it sets the key version to 0 and updates the cache. Otherwise, it removes the key completely.
*
* @param string $key Cache key.
* @param string $group Cache group. Default is an empty string.
*
* @return bool True on success, false on failure.
*/
public function delete( $key, $group = '' ) {
$storage_key = $this->get_item_key( $key );
if ( $this->_use_expired_data ) {
$v = @$this->_memcache->get( $storage_key );
if ( is_array( $v ) ) {
$v['key_version'] = 0;
@$this->_memcache->set( $storage_key, $v, false, 0 );
return true;
}
}
return @$this->_memcache->delete( $storage_key, 0 );
}
/**
* Deletes a key and its value from the cache without considering versioning.
*
* @param string $key Cache key to delete.
* @param string $group Cache group. Default is an empty string.
*
* @return bool True on success, false on failure.
*/
public function hard_delete( $key, $group = '' ) {
$storage_key = $this->get_item_key( $key );
return @$this->_memcache->delete( $storage_key, 0 );
}
/**
* Flushes the cache for the specified group by incrementing its key version.
*
* @param string $group Cache group. Default is an empty string.
*
* @return bool Always returns true.
*/
public function flush( $group = '' ) {
$this->_increment_key_version( $group );
return true;
}
/**
* Prepares an ahead-generation extension for cache key versioning.
*
* Used to create a new version of a cache key for precomputing or updating data.
*
* @param string $group Cache group.
*
* @return array Associative array with:
* - 'key_version' (int): The new key version.
* - 'key_version_at_creation' (int): The current key version.
*/
public function get_ahead_generation_extension( $group ) {
$v = $this->_get_key_version( $group );
return array(
'key_version' => $v + 1,
'key_version_at_creation' => $v,
);
}
/**
* Updates the cache key version after an ahead-generation operation.
*
* @param string $group Cache group.
* @param array $extension {
* The extension data with the new key version.
*
* @type string $key_version The new cache key version.
* }
*
* @return void
*/
public function flush_group_after_ahead_generation( $group, $extension ) {
$v = $this->_get_key_version( $group );
if ( $extension['key_version'] > $v ) {
$this->_set_key_version( $extension['key_version'], $group );
}
}
/**
* Checks if the Memcache extension is available.
*
* @return bool True if Memcache is available, false otherwise.
*/
public function available() {
return class_exists( 'Memcache' );
}
/**
* Retrieves statistics about the Memcache instance.
*
* @return array|false An associative array of Memcache statistics, or false on failure.
*/
public function get_statistics() {
return $this->_memcache->getStats();
}
/**
* Gets the current key version for a cache group.
*
* @param string $group Cache group. Default is an empty string.
*
* @return int The current key version.
*/
private function _get_key_version( $group = '' ) {
if ( ! isset( $this->_key_version[ $group ] ) || $this->_key_version[ $group ] <= 0 ) {
$v = @$this->_memcache->get( $this->_get_key_version_key( $group ) );
$v = intval( $v );
$this->_key_version[ $group ] = ( $v > 0 ? $v : 1 );
}
return $this->_key_version[ $group ];
}
/**
* Sets a new key version for a cache group.
*
* @param int $v The new key version.
* @param string $group Cache group. Default is an empty string.
*
* @return void
*/
private function _set_key_version( $v, $group = '' ) {
// expiration has to be as long as possible since all cache data expires when key version expires.
@$this->_memcache->set( $this->_get_key_version_key( $group ), $v, false, 0 );
$this->_key_version[ $group ] = $v;
}
/**
* Increments the key version for a cache group.
*
* If the key does not exist, initializes it with version 2.
*
* @since 0.14.5
*
* @param string $group Cache group. Default is an empty string.
*
* @return void
*/
private function _increment_key_version( $group = '' ) {
$r = @$this->_memcache->increment( $this->_get_key_version_key( $group ), 1 );
if ( $r ) {
$this->_key_version[ $group ] = $r;
} else {
// it doesn't initialize the key if it doesn't exist.
$this->_set_key_version( 2, $group );
}
}
/**
* Retrieves the size and item count of the cache.
*
* This method collects statistics about the size of the cache and the number of items stored in it.
*
* @param int $timeout_time The timeout duration for retrieving stats.
*
* @return array Associative array with:
* - 'bytes' (int): Total size of the cached items in bytes.
* - 'items' (int): Total number of cached items.
* - 'timeout_occurred' (bool): Whether a timeout occurred while retrieving stats.
*/
public function get_stats_size( $timeout_time ) {
$size = array(
'bytes' => 0,
'items' => 0,
'timeout_occurred' => false,
);
$key_prefix = $this->get_item_key( '' );
$slabs = @$this->_memcache->getExtendedStats( 'slabs' );
$slabs_plain = array();
if ( is_array( $slabs ) ) {
foreach ( $slabs as $server => $server_slabs ) {
foreach ( $server_slabs as $slab_id => $slab_meta ) {
if ( (int) $slab_id > 0 ) {
$slabs_plain[ (int) $slab_id ] = '*';
}
}
}
}
foreach ( $slabs_plain as $slab_id => $nothing ) {
$cdump = @$this->_memcache->getExtendedStats( 'cachedump', (int) $slab_id );
if ( ! is_array( $cdump ) ) {
continue;
}
foreach ( $cdump as $server => $keys_data ) {
if ( ! is_array( $keys_data ) ) {
continue;
}
foreach ( $keys_data as $key => $size_expiration ) {
if ( substr( $key, 0, strlen( $key_prefix ) ) === $key_prefix ) {
if ( count( $size_expiration ) > 0 ) {
$size['bytes'] += $size_expiration[0];
++$size['items'];
}
}
}
}
}
return $size;
}
/**
* Conditionally sets a new value if the current value matches the old value.
*
* Since Memcache does not support Compare-And-Swap (CAS), atomicity cannot be guaranteed.
*
* @param string $key The cache key.
* @param array $old_value {
* The expected old value.
*
* @type mixed $content The content to match against.
* }
* @param array $new_value The new value to set if the old value matches.
*
* @return bool True if the value was set, false otherwise.
*/
public function set_if_maybe_equals( $key, $old_value, $new_value ) {
// cant guarantee atomic action here, memcache doesnt support CAS.
$value = $this->get( $key );
if ( isset( $old_value['content'] ) && $value['content'] !== $old_value['content'] ) {
return false;
}
return $this->set( $key, $new_value );
}
/**
* Adds a value to a counter stored in the cache.
*
* If the counter does not exist, it initializes the counter to 0 before adding the value.
*
* @param string $key The cache key for the counter.
* @param int $value The value to add to the counter. If 0, no changes are made.
*
* @return int|bool The new counter value on success, or false on failure.
*/
public function counter_add( $key, $value ) {
if ( 0 === $value ) {
return true;
}
$storage_key = $this->get_item_key( $key );
$r = @$this->_memcache->increment( $storage_key, $value );
if ( ! $r ) { // it doesnt initialize counter by itself.
$this->counter_set( $key, 0 );
}
return $r;
}
/**
* Sets a counter to a specific value.
*
* @param string $key The cache key for the counter.
* @param int $value The value to set for the counter.
*
* @return bool True on success, false on failure.
*/
public function counter_set( $key, $value ) {
$storage_key = $this->get_item_key( $key );
return @$this->_memcache->set( $storage_key, $value );
}
/**
* Retrieves the current value of a counter stored in the cache.
*
* @param string $key The cache key for the counter.
*
* @return int The counter value. Returns 0 if the counter does not exist.
*/
public function counter_get( $key ) {
$storage_key = $this->get_item_key( $key );
$v = (int) @$this->_memcache->get( $storage_key );
return $v;
}
/**
* Generates a unique storage key for a given cache item.
*
* The key includes the instance ID, host, blog ID, module, and an MD5 hash of the item name. Spaces in the name are sanitized
* to ensure compatibility with Memcache.
*
* @param string $name The name of the cache item.
*
* @return string The unique storage key for the cache item.
*/
public function get_item_key( $name ) {
// memcached doesn't survive spaces in a key.
$key = sprintf( 'w3tc_%d_%s_%d_%s_%s', $this->_instance_id, $this->_host, $this->_blog_id, $this->_module, md5( $name ) );
return $key;
}
}