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Add faux-flush support #49

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Add faux-flush support #49

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f3d3d89
add faux-flush support
webaware Nov 14, 2014
655295f
fix l10n esc_html() calls on admin messages
webaware Nov 15, 2014
7391c0a
restrict faux-flush admin access to super admins on multisite
webaware Nov 15, 2014
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126 changes: 124 additions & 2 deletions object-cache.php
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Original file line number Diff line number Diff line change
Expand Up @@ -808,6 +808,13 @@ class WP_Object_Cache {
*/
public $blog_prefix = '';

/**
* Salt allowing cache to be faux-flushed.
*
* @var string
*/
protected $faux_flush_key = '';

/**
* Instantiate the Memcached class.
*
Expand Down Expand Up @@ -849,6 +856,17 @@ public function __construct( $persistent_id = NULL ) {
// Setup cacheable values for handling expiration times
$this->thirty_days = 60 * 60 * 24 * 30;
$this->now = time();

// enable faux-flush of cache, so that websites sharing a Memcached instance don't flush each other
if ( defined( 'WP_CACHE_FAUX_FLUSH' ) && WP_CACHE_FAUX_FLUSH ) {
$this->faux_flush_key = $this->get( 'memcached_faux_flush_key', 'site-options' );
if ( empty( $this->faux_flush_key ) ) {
$this->replaceFauxFlushKey();
}

// enable admin menu items
add_action('admin_menu', array( $this, 'adminMenu' ) );
}
}

/**
Expand Down Expand Up @@ -1247,7 +1265,14 @@ public function fetchAll() {
* @return bool Returns TRUE on success or FALSE on failure.
*/
public function flush( $delay = 0 ) {
$result = $this->m->flush( $delay );
if ( $this->faux_flush_key ) {
// don't actually flush Memcached, just change a salt used to access cached items; they are now "forgotten"
$result = $this->replaceFauxFlushKey();
}
else {
// ask Memcached to flush
$result = $this->m->flush( $delay );
}

// Only reset the runtime cache if memcached was properly flushed
if ( Memcached::RES_SUCCESS === $this->getResultCode() )
Expand Down Expand Up @@ -1912,7 +1937,10 @@ public function buildKey( $key, $group = 'default' ) {
else
$prefix = $this->blog_prefix;

return preg_replace( '/\s+/', '', WP_CACHE_KEY_SALT . "$prefix$group:$key" );
// support faux-flush by adding a faux-flush suffix
$faux_flush = $this->faux_flush_key ? ':' . $this->faux_flush_key : '';

return preg_replace( '/\s+/', '', WP_CACHE_KEY_SALT . "$prefix$group:$key$faux_flush" );
}

/**
Expand Down Expand Up @@ -2103,4 +2131,98 @@ public function switch_to_blog( $blog_id ) {
$blog_id = (int) $blog_id;
$this->blog_prefix = ( is_multisite() ? $blog_id : $table_prefix ) . ':';
}

/**
* Add items to WordPress admin menu
*/
public function adminMenu() {
if ( is_multisite() ) {
// only give access to Super Admins on multisite
$capability = 'manage_network_options';
}
else {
// only give acces to Admins on single sites
$capability = 'manage_options';
}

$label = __( 'Object Caching', 'wordpress-pecl-memcached-object-cache' );
add_management_page( $label, $label, $capability, 'pecl-memcached', array($this, 'toolsPage'));
}

/**
* Manage the tools page in WordPress admin.
*/
public function toolsPage() {

// maybe process a faux-flush request
if ( ! empty( $_POST[ 'submit' ] ) ) {
check_admin_referer( 'faux-flush', 'pecl_memcached_nonce' );

$result = $this->flush();

if ( $result ) {
$message = esc_html__( 'Memcached object cache was faux-flushed.', 'wordpress-pecl-memcached-object-cache' );
}
else {
$code = $this->getResultCode();
$error = sprintf( esc_html__( 'Faux-flush of object cache failed; error code = %s.', 'wordpress-pecl-memcached-object-cache' ), $code );
}
}

$form_url = admin_url( 'tools.php?page=pecl-memcached' );
?>

<div class="wrap">

<h2><?php esc_html_e( 'WordPress PECL Memcached Object Cache', 'wordpress-pecl-memcached-object-cache' ); ?></h2>

<p><?php esc_html_e( 'Faux-flush allows websites sharing a Memcached instance to clear the object cache without impacting each other.', 'wordpress-pecl-memcached-object-cache' ); ?></p>

<?php if ( ! empty( $message ) ): ?>
<div class="updated"><p><?php echo $message; ?></p></div>
<?php endif; ?>

<?php if ( ! empty( $error ) ): ?>
<div class="error"><p><?php echo $error; ?></p></div>
<?php endif; ?>

<form action="<?php echo $form_url; ?>" method="POST">
<?php submit_button( __( 'Faux-flush cache', 'wordpress-pecl-memcached-object-cache' ) ); ?>
<?php wp_nonce_field( 'faux-flush', 'pecl_memcached_nonce', false ); ?>
</form>

</div>

<?php
}

/**
* Generate a new faux-flush key.
*
* This permits websites to "flush the cache" without really flushing Memcached.
* The website simply "forgets" how to access the old cached data, which will eventually be evicted from the cache.
*
* @return bool Returns TRUE on success or FALSE on failure.
*/
protected function replaceFauxFlushKey() {
// record old faux-flush key, and reset so that key is saved without a faux-flush key
$old_faux_flush_key = $this->faux_flush_key;
$this->faux_flush_key = '';

// generate and attempt to save new key
$faux_flush_key = uniqid( 'FFK' );
$result = $this->set( 'memcached_faux_flush_key', $faux_flush_key, 'site-options' );

if ( $result ) {
// accept new faux-flush key
$this->faux_flush_key = $faux_flush_key;
}
else {
// couldn't set new key, must restore old key
$this->faux_flush_key = $old_faux_flush_key;
}

return $result;
}

}