wikimedia /
mediawiki
Duplicate code is one of the most pungent code smells. A rule that is often used is to re-structure code once it is duplicated in three or more places.
Common duplication problems, and corresponding solutions are:
Complex classes like LBFactory often do a lot of different things. To break such a class down, we need to identify a cohesive component within that class. A common approach to find such a component is to look for fields/methods that share the same prefixes, or suffixes. You can also have a look at the cohesion graph to spot any un-connected, or weakly-connected components.
Once you have determined the fields that belong together, you can apply the Extract Class refactoring. If the component makes sense as a sub-class, Extract Subclass is also a candidate, and is often faster.
While breaking up the class, it is a good idea to analyze how other classes use LBFactory, and based on these observations, apply Extract Interface, too.
| 1 | <?php |
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| 33 | abstract class LBFactory implements DestructibleService { |
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| 34 | /** @var ChronologyProtector */ |
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| 35 | protected $chronProt; |
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| 36 | /** @var TransactionProfiler */ |
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| 37 | protected $trxProfiler; |
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| 38 | /** @var LoggerInterface */ |
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| 39 | protected $trxLogger; |
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| 40 | /** @var BagOStuff */ |
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| 41 | protected $srvCache; |
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| 42 | /** @var WANObjectCache */ |
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| 43 | protected $wanCache; |
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| 44 | |||
| 45 | /** @var mixed */ |
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| 46 | protected $ticket; |
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| 47 | /** @var string|bool String if a requested DBO_TRX transaction round is active */ |
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| 48 | protected $trxRoundId = false; |
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| 49 | /** @var string|bool Reason all LBs are read-only or false if not */ |
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| 50 | protected $readOnlyReason = false; |
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| 51 | /** @var callable[] */ |
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| 52 | protected $replicationWaitCallbacks = []; |
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| 53 | |||
| 54 | const SHUTDOWN_NO_CHRONPROT = 1; // don't save ChronologyProtector positions (for async code) |
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| 55 | |||
| 56 | /** |
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| 57 | * Construct a factory based on a configuration array (typically from $wgLBFactoryConf) |
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| 58 | * @param array $conf |
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| 59 | * @TODO: inject objects via dependency framework |
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| 60 | */ |
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| 61 | public function __construct( array $conf ) { |
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| 83 | |||
| 84 | /** |
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| 85 | * Disables all load balancers. All connections are closed, and any attempt to |
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| 86 | * open a new connection will result in a DBAccessError. |
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| 87 | * @see LoadBalancer::disable() |
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| 88 | */ |
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| 89 | public function destroy() { |
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| 93 | |||
| 94 | /** |
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| 95 | * Disables all access to the load balancer, will cause all database access |
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| 96 | * to throw a DBAccessError |
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| 97 | */ |
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| 98 | public static function disableBackend() { |
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| 101 | |||
| 102 | /** |
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| 103 | * Get an LBFactory instance |
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| 104 | * |
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| 105 | * @deprecated since 1.27, use MediaWikiServices::getDBLoadBalancerFactory() instead. |
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| 106 | * |
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| 107 | * @return LBFactory |
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| 108 | */ |
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| 109 | public static function singleton() { |
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| 112 | |||
| 113 | /** |
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| 114 | * Returns the LBFactory class to use and the load balancer configuration. |
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| 115 | * |
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| 116 | * @todo instead of this, use a ServiceContainer for managing the different implementations. |
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| 117 | * |
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| 118 | * @param array $config (e.g. $wgLBFactoryConf) |
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| 119 | * @return string Class name |
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| 120 | */ |
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| 121 | public static function getLBFactoryClass( array $config ) { |
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| 143 | |||
| 144 | /** |
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| 145 | * Shut down, close connections and destroy the cached instance. |
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| 146 | * |
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| 147 | * @deprecated since 1.27, use LBFactory::destroy() |
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| 148 | */ |
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| 149 | public static function destroyInstance() { |
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| 152 | |||
| 153 | /** |
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| 154 | * Create a new load balancer object. The resulting object will be untracked, |
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| 155 | * not chronology-protected, and the caller is responsible for cleaning it up. |
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| 156 | * |
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| 157 | * @param bool|string $wiki Wiki ID, or false for the current wiki |
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| 158 | * @return LoadBalancer |
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| 159 | */ |
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| 160 | abstract public function newMainLB( $wiki = false ); |
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| 161 | |||
| 162 | /** |
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| 163 | * Get a cached (tracked) load balancer object. |
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| 164 | * |
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| 165 | * @param bool|string $wiki Wiki ID, or false for the current wiki |
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| 166 | * @return LoadBalancer |
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| 167 | */ |
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| 168 | abstract public function getMainLB( $wiki = false ); |
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| 169 | |||
| 170 | /** |
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| 171 | * Create a new load balancer for external storage. The resulting object will be |
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| 172 | * untracked, not chronology-protected, and the caller is responsible for |
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| 173 | * cleaning it up. |
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| 174 | * |
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| 175 | * @param string $cluster External storage cluster, or false for core |
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| 176 | * @param bool|string $wiki Wiki ID, or false for the current wiki |
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| 177 | * @return LoadBalancer |
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| 178 | */ |
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| 179 | abstract protected function newExternalLB( $cluster, $wiki = false ); |
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| 180 | |||
| 181 | /** |
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| 182 | * Get a cached (tracked) load balancer for external storage |
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| 183 | * |
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| 184 | * @param string $cluster External storage cluster, or false for core |
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| 185 | * @param bool|string $wiki Wiki ID, or false for the current wiki |
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| 186 | * @return LoadBalancer |
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| 187 | */ |
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| 188 | abstract public function getExternalLB( $cluster, $wiki = false ); |
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| 189 | |||
| 190 | /** |
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| 191 | * Execute a function for each tracked load balancer |
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| 192 | * The callback is called with the load balancer as the first parameter, |
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| 193 | * and $params passed as the subsequent parameters. |
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| 194 | * |
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| 195 | * @param callable $callback |
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| 196 | * @param array $params |
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| 197 | */ |
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| 198 | abstract public function forEachLB( $callback, array $params = [] ); |
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| 199 | |||
| 200 | /** |
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| 201 | * Prepare all tracked load balancers for shutdown |
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| 202 | * @param integer $flags Supports SHUTDOWN_* flags |
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| 203 | */ |
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| 204 | public function shutdown( $flags = 0 ) { |
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| 205 | if ( !( $flags & self::SHUTDOWN_NO_CHRONPROT ) ) { |
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| 206 | $this->shutdownChronologyProtector( $this->chronProt ); |
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| 207 | } |
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| 208 | $this->commitMasterChanges( __METHOD__ ); // sanity |
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| 209 | } |
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| 210 | |||
| 211 | /** |
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| 212 | * Call a method of each tracked load balancer |
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| 213 | * |
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| 214 | * @param string $methodName |
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| 215 | * @param array $args |
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| 216 | */ |
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| 217 | private function forEachLBCallMethod( $methodName, array $args = [] ) { |
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| 225 | |||
| 226 | /** |
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| 227 | * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set) |
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| 228 | * |
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| 229 | * The DBO_TRX setting will be reverted to the default in each of these methods: |
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| 230 | * - commitMasterChanges() |
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| 231 | * - rollbackMasterChanges() |
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| 232 | * - commitAll() |
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| 233 | * |
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| 234 | * This allows for custom transaction rounds from any outer transaction scope. |
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| 235 | * |
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| 236 | * @param string $fname |
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| 237 | * @throws DBTransactionError |
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| 238 | * @since 1.28 |
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| 239 | */ |
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| 240 | public function beginMasterChanges( $fname = __METHOD__ ) { |
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| 251 | |||
| 252 | /** |
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| 253 | * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot |
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| 254 | * |
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| 255 | * @param string $fname Caller name |
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| 256 | * @since 1.28 |
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| 257 | */ |
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| 258 | public function flushReplicaSnapshots( $fname = __METHOD__ ) { |
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| 261 | |||
| 262 | /** |
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| 263 | * Commit on all connections. Done for two reasons: |
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| 264 | * 1. To commit changes to the masters. |
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| 265 | * 2. To release the snapshot on all connections, master and replica DB. |
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| 266 | * @param string $fname Caller name |
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| 267 | * @param array $options Options map: |
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| 268 | * - maxWriteDuration: abort if more than this much time was spent in write queries |
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| 269 | */ |
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| 270 | public function commitAll( $fname = __METHOD__, array $options = [] ) { |
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| 274 | |||
| 275 | /** |
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| 276 | * Commit changes on all master connections |
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| 277 | * @param string $fname Caller name |
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| 278 | * @param array $options Options map: |
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| 279 | * - maxWriteDuration: abort if more than this much time was spent in write queries |
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| 280 | * @throws Exception |
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| 281 | */ |
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| 282 | public function commitMasterChanges( $fname = __METHOD__, array $options = [] ) { |
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| 312 | |||
| 313 | /** |
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| 314 | * Rollback changes on all master connections |
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| 315 | * @param string $fname Caller name |
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| 316 | * @since 1.23 |
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| 317 | */ |
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| 318 | public function rollbackMasterChanges( $fname = __METHOD__ ) { |
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| 327 | |||
| 328 | /** |
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| 329 | * Log query info if multi DB transactions are going to be committed now |
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| 330 | */ |
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| 331 | private function logIfMultiDbTransaction() { |
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| 350 | |||
| 351 | /** |
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| 352 | * Determine if any master connection has pending changes |
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| 353 | * @return bool |
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| 354 | * @since 1.23 |
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| 355 | */ |
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| 356 | public function hasMasterChanges() { |
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| 364 | |||
| 365 | /** |
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| 366 | * Detemine if any lagged replica DB connection was used |
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| 367 | * @return bool |
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| 368 | * @since 1.28 |
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| 369 | */ |
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| 370 | public function laggedReplicaUsed() { |
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| 378 | |||
| 379 | /** |
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| 380 | * @return bool |
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| 381 | * @since 1.27 |
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| 382 | * @deprecated Since 1.28; use laggedReplicaUsed() |
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| 383 | */ |
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| 384 | public function laggedSlaveUsed() { |
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| 387 | |||
| 388 | /** |
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| 389 | * Determine if any master connection has pending/written changes from this request |
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| 390 | * @return bool |
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| 391 | * @since 1.27 |
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| 392 | */ |
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| 393 | public function hasOrMadeRecentMasterChanges() { |
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| 400 | |||
| 401 | /** |
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| 402 | * Waits for the replica DBs to catch up to the current master position |
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| 403 | * |
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| 404 | * Use this when updating very large numbers of rows, as in maintenance scripts, |
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| 405 | * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs. |
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| 406 | * |
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| 407 | * By default this waits on all DB clusters actually used in this request. |
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| 408 | * This makes sense when lag being waiting on is caused by the code that does this check. |
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| 409 | * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters |
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| 410 | * that were not changed since the last wait check. To forcefully wait on a specific cluster |
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| 411 | * for a given wiki, use the 'wiki' parameter. To forcefully wait on an "external" cluster, |
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| 412 | * use the "cluster" parameter. |
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| 413 | * |
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| 414 | * Never call this function after a large DB write that is *still* in a transaction. |
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| 415 | * It only makes sense to call this after the possible lag inducing changes were committed. |
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| 416 | * |
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| 417 | * @param array $opts Optional fields that include: |
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| 418 | * - wiki : wait on the load balancer DBs that handles the given wiki |
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| 419 | * - cluster : wait on the given external load balancer DBs |
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| 420 | * - timeout : Max wait time. Default: ~60 seconds |
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| 421 | * - ifWritesSince: Only wait if writes were done since this UNIX timestamp |
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| 422 | * @throws DBReplicationWaitError If a timeout or error occured waiting on a DB cluster |
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| 423 | * @since 1.27 |
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| 424 | */ |
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| 425 | public function waitForReplication( array $opts = [] ) { |
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| 488 | |||
| 489 | /** |
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| 490 | * Add a callback to be run in every call to waitForReplication() before waiting |
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| 491 | * |
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| 492 | * Callbacks must clear any transactions that they start |
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| 493 | * |
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| 494 | * @param string $name Callback name |
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| 495 | * @param callable|null $callback Use null to unset a callback |
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| 496 | * @since 1.28 |
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| 497 | */ |
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| 498 | public function setWaitForReplicationListener( $name, callable $callback = null ) { |
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| 505 | |||
| 506 | /** |
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| 507 | * Get a token asserting that no transaction writes are active |
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| 508 | * |
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| 509 | * @param string $fname Caller name (e.g. __METHOD__) |
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| 510 | * @return mixed A value to pass to commitAndWaitForReplication() |
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| 511 | * @since 1.28 |
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| 512 | */ |
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| 513 | public function getEmptyTransactionTicket( $fname ) { |
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| 521 | |||
| 522 | /** |
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| 523 | * Convenience method for safely running commitMasterChanges()/waitForReplication() |
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| 524 | * |
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| 525 | * This will commit and wait unless $ticket indicates it is unsafe to do so |
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| 526 | * |
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| 527 | * @param string $fname Caller name (e.g. __METHOD__) |
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| 528 | * @param mixed $ticket Result of getEmptyTransactionTicket() |
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| 529 | * @param array $opts Options to waitForReplication() |
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| 530 | * @throws DBReplicationWaitError |
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| 531 | * @since 1.28 |
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| 532 | */ |
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| 533 | public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] ) { |
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| 557 | |||
| 558 | /** |
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| 559 | * Disable the ChronologyProtector for all load balancers |
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| 560 | * |
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| 561 | * This can be called at the start of special API entry points |
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| 562 | * |
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| 563 | * @since 1.27 |
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| 564 | */ |
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| 565 | public function disableChronologyProtection() { |
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| 568 | |||
| 569 | /** |
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| 570 | * @return ChronologyProtector |
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| 571 | */ |
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| 572 | protected function newChronologyProtector() { |
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| 591 | |||
| 592 | /** |
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| 593 | * @param ChronologyProtector $cp |
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| 594 | */ |
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| 595 | protected function shutdownChronologyProtector( ChronologyProtector $cp ) { |
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| 613 | |||
| 614 | /** |
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| 615 | * @param LoadBalancer $lb |
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| 616 | */ |
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| 617 | protected function initLoadBalancer( LoadBalancer $lb ) { |
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| 622 | |||
| 623 | /** |
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| 624 | * Close all open database connections on all open load balancers. |
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| 625 | * @since 1.28 |
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| 626 | */ |
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| 627 | public function closeAll() { |
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| 630 | |||
| 631 | } |
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| 632 |
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