*/
define( 'MSG_LOAD_TIMEOUT', 60 );
-/**
- * Memcached timeout when locking a key for a writing operation.
- * See MessageCache::lock()
- */
-define( 'MSG_LOCK_TIMEOUT', 30 );
-/**
- * Number of times we will try to acquire a lock from Memcached.
- * This comes in addition to MSG_LOCK_TIMEOUT.
- */
-define( 'MSG_WAIT_TIMEOUT', 30 );
-
/**
* Message cache
* Performs various MediaWiki namespace-related functions
class MessageCache {
const FOR_UPDATE = 1; // force message reload
+ /** How long memcached locks last */
+ const WAIT_SEC = 30;
+ /** How long to wait for memcached locks */
+ const LOCK_TTL = 30;
+
/**
* Process local cache of loaded messages that are defined in
* MediaWiki namespace. First array level is a language code,
$this->mExpiry = $expiry;
if ( $wgUseLocalMessageCache ) {
- $this->localCache = ObjectCache::newAccelerator( array(), CACHE_NONE );
+ $this->localCache = ObjectCache::newAccelerator( CACHE_NONE );
} else {
$this->localCache = wfGetCache( CACHE_NONE );
}
*/
protected function getLocalCache( $code ) {
$cacheKey = wfMemcKey( __CLASS__, $code );
+
return $this->localCache->get( $cacheKey );
}
* @return bool
*/
function load( $code = false, $mode = null ) {
- global $wgUseLocalMessageCache;
-
if ( !is_string( $code ) ) {
# This isn't really nice, so at least make a note about it and try to
# fall back
# or local cache goes out of date (e.g. due to replace() on some other server)
list( $hash, $hashVolatile ) = $this->getValidationHash( $code );
- if ( $wgUseLocalMessageCache && $hash ) {
- # Try the local cache and check against the cluster hash key...
- $cache = $this->getLocalCache( $code );
- if ( !$cache ) {
- $where[] = 'local cache is empty';
- } elseif ( !isset( $cache['HASH'] ) || $cache['HASH'] !== $hash ) {
- $where[] = 'local cache has the wrong hash';
- $staleCache = $cache;
- } elseif ( $this->isCacheExpired( $cache ) ) {
- $where[] = 'local cache is expired';
- $staleCache = $cache;
- } elseif ( $hashVolatile ) {
- $where[] = 'local cache validation key is expired/volatile';
- $staleCache = $cache;
- } else {
- $where[] = 'got from local cache';
- $success = true;
- $this->mCache[$code] = $cache;
- }
+ # Try the local cache and check against the cluster hash key...
+ $cache = $this->getLocalCache( $code );
+ if ( !$cache ) {
+ $where[] = 'local cache is empty';
+ } elseif ( !isset( $cache['HASH'] ) || $cache['HASH'] !== $hash ) {
+ $where[] = 'local cache has the wrong hash';
+ $staleCache = $cache;
+ } elseif ( $this->isCacheExpired( $cache ) ) {
+ $where[] = 'local cache is expired';
+ $staleCache = $cache;
+ } elseif ( $hashVolatile ) {
+ $where[] = 'local cache validation key is expired/volatile';
+ $staleCache = $cache;
+ } else {
+ $where[] = 'got from local cache';
+ $success = true;
+ $this->mCache[$code] = $cache;
}
if ( !$success ) {
# Disable cache
break;
} else {
- # Wait for the other thread to finish, then retry
+ # Wait for the other thread to finish, then retry. Normally,
+ # the memcached get() will then yeild the other thread's result.
$where[] = 'waited for other thread to complete';
- $this->lock( $cacheKey );
- $this->unlock( $cacheKey );
+ $this->getReentrantScopedLock( $cacheKey );
}
}
}
$memCache = $this->mMemc;
+ # Get the non-blocking status key lock. This lets the caller quickly know
+ # to use any stale cache lying around. Otherwise, it may do a blocking
+ # lock to try to obtain the messages.
$statusKey = wfMemcKey( 'messages', $code, 'status' );
if ( !$memCache->add( $statusKey, 'loading', MSG_LOAD_TIMEOUT ) ) {
return false; // could not acquire lock
# If this lock fails, it doesn't really matter, it just means the
# write is potentially non-atomic, e.g. the results of a replace()
# may be discarded.
- if ( $this->lock( $cacheKey ) ) {
- $that = $this;
- $mainUnlocker = new ScopedCallback( function () use ( $that, $cacheKey ) {
- $that->unlock( $cacheKey );
- } );
- } else {
- $mainUnlocker = null;
+ $mainUnlocker = $this->getReentrantScopedLock( $cacheKey );
+ if ( !$mainUnlocker ) {
$where[] = 'could not acquire main lock';
}
return;
}
+ # Note that if the cache is volatile, load() may trigger a DB fetch.
+ # In that case we reenter/reuse the existing cache key lock to avoid
+ # a self-deadlock. This is safe as no reads happen *directly* in this
+ # method between getReentrantScopedLock() and load() below. There is
+ # no risk of data "changing under our feet" for replace().
$cacheKey = wfMemcKey( 'messages', $code );
- $this->lock( $cacheKey );
+ $scopedLock = $this->getReentrantScopedLock( $cacheKey );
$this->load( $code, self::FOR_UPDATE );
$titleKey = wfMemcKey( 'messages', 'individual', $title );
if ( $text === false ) {
# Article was deleted
$this->mCache[$code][$title] = '!NONEXISTENT';
- $this->mMemc->delete( $titleKey );
+ $this->wanCache->delete( $titleKey );
} elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
# Check for size
$this->mCache[$code][$title] = '!TOO BIG';
- $this->mMemc->set( $titleKey, ' ' . $text, $this->mExpiry );
+ $this->wanCache->set( $titleKey, ' ' . $text, $this->mExpiry );
} else {
$this->mCache[$code][$title] = ' ' . $text;
- $this->mMemc->delete( $titleKey );
+ $this->wanCache->delete( $titleKey );
}
# Update caches
$this->saveToCaches( $this->mCache[$code], 'all', $code );
- $this->unlock( $cacheKey );
+ ScopedCallback::consume( $scopedLock );
$this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );
// Also delete cached sidebar... just in case it is affected
* @return bool
*/
protected function saveToCaches( $cache, $dest, $code = false ) {
- global $wgUseLocalMessageCache;
-
if ( $dest === 'all' ) {
$cacheKey = wfMemcKey( 'messages', $code );
$success = $this->mMemc->set( $cacheKey, $cache );
$this->setValidationHash( $code, $cache['HASH'] );
# Save to local cache
- if ( $wgUseLocalMessageCache ) {
- $this->saveToLocalCache( $code, $cache );
- }
+ $this->saveToLocalCache( $code, $cache );
return $success;
}
}
/**
- * Represents a write lock on the messages key.
- *
- * Will retry MessageCache::MSG_WAIT_TIMEOUT times, each operations having
- * a timeout of MessageCache::MSG_LOCK_TIMEOUT.
- *
- * @param string $key
- * @return bool Success
+ * @param string $key A language message cache key that stores blobs
+ * @return null|ScopedCallback
*/
- function lock( $key ) {
- $lockKey = $key . ':lock';
- $acquired = false;
- $testDone = false;
- for ( $i = 0; $i < MSG_WAIT_TIMEOUT && !$acquired; $i++ ) {
- $acquired = $this->mMemc->add( $lockKey, 1, MSG_LOCK_TIMEOUT );
- if ( $acquired ) {
- break;
- }
-
- # Fail fast if memcached is totally down
- if ( !$testDone ) {
- $testDone = true;
- if ( !$this->mMemc->set( wfMemcKey( 'test' ), 'test', 1 ) ) {
- break;
- }
- }
- sleep( 1 );
- }
-
- return $acquired;
- }
-
- function unlock( $key ) {
- $lockKey = $key . ':lock';
- $this->mMemc->delete( $lockKey );
+ protected function getReentrantScopedLock( $key ) {
+ return $this->mMemc->getScopedLock( $key, self::WAIT_SEC, self::LOCK_TTL, __METHOD__ );
}
/**
# Try the individual message cache
$titleKey = wfMemcKey( 'messages', 'individual', $title );
- $entry = $this->mMemc->get( $titleKey );
+ $entry = $this->wanCache->get( $titleKey );
if ( $entry ) {
if ( substr( $entry, 0, 1 ) === ' ' ) {
$this->mCache[$code][$title] = $entry;
return false;
} else {
# Corrupt/obsolete entry, delete it
- $this->mMemc->delete( $titleKey );
+ $this->wanCache->delete( $titleKey );
}
}
# Try loading it from the database
- $revision = Revision::newFromTitle(
- Title::makeTitle( NS_MEDIAWIKI, $title ), false, Revision::READ_LATEST
- );
+ $revision = Revision::newFromTitle( Title::makeTitle( NS_MEDIAWIKI, $title ) );
if ( $revision ) {
$content = $revision->getContent();
if ( !$content ) {
$message = false; // negative caching
} else {
$this->mCache[$code][$title] = ' ' . $message;
- $this->mMemc->set( $titleKey, ' ' . $message, $this->mExpiry );
+ $this->wanCache->set( $titleKey, ' ' . $message, $this->mExpiry );
}
}
} else {
if ( $message === false ) { // negative caching
$this->mCache[$code][$title] = '!NONEXISTENT';
- $this->mMemc->set( $titleKey, '!NONEXISTENT', $this->mExpiry );
+ $this->wanCache->set( $titleKey, '!NONEXISTENT', $this->mExpiry );
}
return $message;
dépôts / lhc / web / wiklou.git / blobdiff