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-rw-r--r--includes/db/LoadMonitor.php129
1 files changed, 37 insertions, 92 deletions
diff --git a/includes/db/LoadMonitor.php b/includes/db/LoadMonitor.php
index 519e2dfd..7281485b 100644
--- a/includes/db/LoadMonitor.php
+++ b/includes/db/LoadMonitor.php
@@ -32,61 +32,35 @@ interface LoadMonitor {
*
* @param LoadBalancer $parent
*/
- function __construct( $parent );
+ public function __construct( $parent );
/**
* Perform pre-connection load ratio adjustment.
- * @param $loads array
- * @param string $group the selected query group
- * @param $wiki String
+ * @param array $loads
+ * @param string|bool $group The selected query group. Default: false
+ * @param string|bool $wiki Default: false
*/
- function scaleLoads( &$loads, $group = false, $wiki = false );
-
- /**
- * Perform post-connection backoff.
- *
- * If the connection is in overload, this should return a backoff factor
- * which will be used to control polling time. The number of threads
- * connected is a good measure.
- *
- * If there is no overload, zero can be returned.
- *
- * A threshold thread count is given, the concrete class may compare this
- * to the running thread count. The threshold may be false, which indicates
- * that the sysadmin has not configured this feature.
- *
- * @param $conn DatabaseBase
- * @param $threshold Float
- */
- function postConnectionBackoff( $conn, $threshold );
+ public function scaleLoads( &$loads, $group = false, $wiki = false );
/**
* Return an estimate of replication lag for each server
*
- * @param $serverIndexes
- * @param $wiki
+ * @param array $serverIndexes
+ * @param string $wiki
*
* @return array
*/
- function getLagTimes( $serverIndexes, $wiki );
+ public function getLagTimes( $serverIndexes, $wiki );
}
-class LoadMonitor_Null implements LoadMonitor {
- function __construct( $parent ) {
- }
-
- function scaleLoads( &$loads, $group = false, $wiki = false ) {
+class LoadMonitorNull implements LoadMonitor {
+ public function __construct( $parent ) {
}
- function postConnectionBackoff( $conn, $threshold ) {
+ public function scaleLoads( &$loads, $group = false, $wiki = false ) {
}
- /**
- * @param $serverIndexes
- * @param $wiki
- * @return array
- */
- function getLagTimes( $serverIndexes, $wiki ) {
+ public function getLagTimes( $serverIndexes, $wiki ) {
return array_fill_keys( $serverIndexes, 0 );
}
}
@@ -97,58 +71,44 @@ class LoadMonitor_Null implements LoadMonitor {
*
* @ingroup Database
*/
-class LoadMonitor_MySQL implements LoadMonitor {
+class LoadMonitorMySQL implements LoadMonitor {
+ /** @var LoadBalancer */
+ public $parent;
+ /** @var BagOStuff */
+ protected $cache;
- /**
- * @var LoadBalancer
- */
- var $parent;
+ public function __construct( $parent ) {
+ global $wgMemc;
- /**
- * @param LoadBalancer $parent
- */
- function __construct( $parent ) {
$this->parent = $parent;
+ $this->cache = $wgMemc ?: wfGetMainCache();
}
- /**
- * @param $loads
- * @param $group bool
- * @param $wiki bool
- */
- function scaleLoads( &$loads, $group = false, $wiki = false ) {
+ public function scaleLoads( &$loads, $group = false, $wiki = false ) {
}
- /**
- * @param $serverIndexes
- * @param $wiki
- * @return array
- */
- function getLagTimes( $serverIndexes, $wiki ) {
+ public function getLagTimes( $serverIndexes, $wiki ) {
if ( count( $serverIndexes ) == 1 && reset( $serverIndexes ) == 0 ) {
// Single server only, just return zero without caching
return array( 0 => 0 );
}
- wfProfileIn( __METHOD__ );
+ $section = new ProfileSection( __METHOD__ );
+
$expiry = 5;
$requestRate = 10;
- global $wgMemc;
- if ( empty( $wgMemc ) ) {
- $wgMemc = wfGetMainCache();
- }
-
+ $cache = $this->cache;
$masterName = $this->parent->getServerName( 0 );
$memcKey = wfMemcKey( 'lag_times', $masterName );
- $times = $wgMemc->get( $memcKey );
+ $times = $cache->get( $memcKey );
if ( is_array( $times ) ) {
# Randomly recache with probability rising over $expiry
$elapsed = time() - $times['timestamp'];
$chance = max( 0, ( $expiry - $elapsed ) * $requestRate );
if ( mt_rand( 0, $chance ) != 0 ) {
unset( $times['timestamp'] ); // hide from caller
- wfProfileOut( __METHOD__ );
+
return $times;
}
wfIncrStats( 'lag_cache_miss_expired' );
@@ -157,15 +117,15 @@ class LoadMonitor_MySQL implements LoadMonitor {
}
# Cache key missing or expired
- if ( $wgMemc->add( "$memcKey:lock", 1, 10 ) ) {
+ if ( $cache->add( "$memcKey:lock", 1, 10 ) ) {
# Let this process alone update the cache value
- $unlocker = new ScopedCallback( function() use ( $wgMemc, $memcKey ) {
- $wgMemc->delete( $memcKey );
+ $unlocker = new ScopedCallback( function () use ( $cache, $memcKey ) {
+ $cache->delete( $memcKey );
} );
} elseif ( is_array( $times ) ) {
# Could not acquire lock but an old cache exists, so use it
unset( $times['timestamp'] ); // hide from caller
- wfProfileOut( __METHOD__ );
+
return $times;
}
@@ -177,34 +137,19 @@ class LoadMonitor_MySQL implements LoadMonitor {
$times[$i] = $conn->getLag();
} elseif ( false !== ( $conn = $this->parent->openConnection( $i, $wiki ) ) ) {
$times[$i] = $conn->getLag();
+ // Close the connection to avoid sleeper connections piling up.
+ // Note that the caller will pick one of these DBs and reconnect,
+ // which is slightly inefficient, but this only matters for the lag
+ // time cache miss cache, which is far less common that cache hits.
+ $this->parent->closeConnection( $conn );
}
}
# Add a timestamp key so we know when it was cached
$times['timestamp'] = time();
- $wgMemc->set( $memcKey, $times, $expiry + 10 );
+ $cache->set( $memcKey, $times, $expiry + 10 );
unset( $times['timestamp'] ); // hide from caller
- wfProfileOut( __METHOD__ );
return $times;
}
-
- /**
- * @param $conn DatabaseBase
- * @param $threshold
- * @return int
- */
- function postConnectionBackoff( $conn, $threshold ) {
- if ( !$threshold ) {
- return 0;
- }
- $status = $conn->getMysqlStatus( "Thread%" );
- if ( $status['Threads_running'] > $threshold ) {
- $server = $conn->getProperty( 'mServer' );
- wfLogDBError( "LB backoff from $server - Threads_running = {$status['Threads_running']}\n" );
- return $status['Threads_connected'];
- } else {
- return 0;
- }
- }
}