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 = 0; // don't save DB positions at all |
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| 55 | const SHUTDOWN_CHRONPROT_ASYNC = 1; // save DB positions, but don't wait on remote DCs |
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| 56 | const SHUTDOWN_CHRONPROT_SYNC = 2; // save DB positions, waiting on all DCs |
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| 57 | |||
| 58 | /** |
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| 59 | * Construct a factory based on a configuration array (typically from $wgLBFactoryConf) |
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| 60 | * @param array $conf |
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| 61 | * @TODO: inject objects via dependency framework |
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| 62 | */ |
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| 63 | public function __construct( array $conf ) { |
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| 85 | |||
| 86 | /** |
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| 87 | * Disables all load balancers. All connections are closed, and any attempt to |
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| 88 | * open a new connection will result in a DBAccessError. |
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| 89 | * @see LoadBalancer::disable() |
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| 90 | */ |
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| 91 | public function destroy() { |
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| 95 | |||
| 96 | /** |
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| 97 | * Disables all access to the load balancer, will cause all database access |
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| 98 | * to throw a DBAccessError |
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| 99 | */ |
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| 100 | public static function disableBackend() { |
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| 103 | |||
| 104 | /** |
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| 105 | * Get an LBFactory instance |
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| 106 | * |
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| 107 | * @deprecated since 1.27, use MediaWikiServices::getDBLoadBalancerFactory() instead. |
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| 108 | * |
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| 109 | * @return LBFactory |
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| 110 | */ |
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| 111 | public static function singleton() { |
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| 114 | |||
| 115 | /** |
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| 116 | * Returns the LBFactory class to use and the load balancer configuration. |
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| 117 | * |
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| 118 | * @todo instead of this, use a ServiceContainer for managing the different implementations. |
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| 119 | * |
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| 120 | * @param array $config (e.g. $wgLBFactoryConf) |
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| 121 | * @return string Class name |
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| 122 | */ |
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| 123 | public static function getLBFactoryClass( array $config ) { |
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| 145 | |||
| 146 | /** |
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| 147 | * Shut down, close connections and destroy the cached instance. |
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| 148 | * |
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| 149 | * @deprecated since 1.27, use LBFactory::destroy() |
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| 150 | */ |
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| 151 | public static function destroyInstance() { |
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| 154 | |||
| 155 | /** |
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| 156 | * Create a new load balancer object. The resulting object will be untracked, |
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| 157 | * not chronology-protected, and the caller is responsible for cleaning it up. |
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| 158 | * |
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| 159 | * @param bool|string $wiki Wiki ID, or false for the current wiki |
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| 160 | * @return LoadBalancer |
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| 161 | */ |
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| 162 | abstract public function newMainLB( $wiki = false ); |
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| 163 | |||
| 164 | /** |
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| 165 | * Get a cached (tracked) load balancer object. |
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| 166 | * |
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| 167 | * @param bool|string $wiki Wiki ID, or false for the current wiki |
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| 168 | * @return LoadBalancer |
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| 169 | */ |
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| 170 | abstract public function getMainLB( $wiki = false ); |
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| 171 | |||
| 172 | /** |
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| 173 | * Create a new load balancer for external storage. The resulting object will be |
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| 174 | * untracked, not chronology-protected, and the caller is responsible for |
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| 175 | * cleaning it up. |
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| 176 | * |
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| 177 | * @param string $cluster External storage cluster, or false for core |
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| 178 | * @param bool|string $wiki Wiki ID, or false for the current wiki |
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| 179 | * @return LoadBalancer |
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| 180 | */ |
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| 181 | abstract protected function newExternalLB( $cluster, $wiki = false ); |
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| 182 | |||
| 183 | /** |
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| 184 | * Get a cached (tracked) load balancer for external storage |
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| 185 | * |
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| 186 | * @param string $cluster External storage cluster, or false for core |
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| 187 | * @param bool|string $wiki Wiki ID, or false for the current wiki |
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| 188 | * @return LoadBalancer |
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| 189 | */ |
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| 190 | abstract public function getExternalLB( $cluster, $wiki = false ); |
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| 191 | |||
| 192 | /** |
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| 193 | * Execute a function for each tracked load balancer |
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| 194 | * The callback is called with the load balancer as the first parameter, |
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| 195 | * and $params passed as the subsequent parameters. |
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| 196 | * |
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| 197 | * @param callable $callback |
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| 198 | * @param array $params |
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| 199 | */ |
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| 200 | abstract public function forEachLB( $callback, array $params = [] ); |
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| 201 | |||
| 202 | /** |
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| 203 | * Prepare all tracked load balancers for shutdown |
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| 204 | * @param integer $mode One of the class SHUTDOWN_* constants |
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| 205 | * @param callable|null $workCallback Work to mask ChronologyProtector writes |
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| 206 | */ |
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| 207 | public function shutdown( |
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| 218 | |||
| 219 | /** |
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| 220 | * Call a method of each tracked load balancer |
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| 221 | * |
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| 222 | * @param string $methodName |
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| 223 | * @param array $args |
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| 224 | */ |
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| 225 | private function forEachLBCallMethod( $methodName, array $args = [] ) { |
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| 233 | |||
| 234 | /** |
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| 235 | * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot |
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| 236 | * |
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| 237 | * @param string $fname Caller name |
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| 238 | * @since 1.28 |
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| 239 | */ |
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| 240 | public function flushReplicaSnapshots( $fname = __METHOD__ ) { |
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| 243 | |||
| 244 | /** |
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| 245 | * Commit on all connections. Done for two reasons: |
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| 246 | * 1. To commit changes to the masters. |
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| 247 | * 2. To release the snapshot on all connections, master and replica DB. |
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| 248 | * @param string $fname Caller name |
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| 249 | * @param array $options Options map: |
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| 250 | * - maxWriteDuration: abort if more than this much time was spent in write queries |
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| 251 | */ |
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| 252 | public function commitAll( $fname = __METHOD__, array $options = [] ) { |
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| 256 | |||
| 257 | /** |
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| 258 | * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set) |
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| 259 | * |
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| 260 | * The DBO_TRX setting will be reverted to the default in each of these methods: |
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| 261 | * - commitMasterChanges() |
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| 262 | * - rollbackMasterChanges() |
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| 263 | * - commitAll() |
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| 264 | * |
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| 265 | * This allows for custom transaction rounds from any outer transaction scope. |
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| 266 | * |
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| 267 | * @param string $fname |
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| 268 | * @throws DBTransactionError |
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| 269 | * @since 1.28 |
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| 270 | */ |
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| 271 | public function beginMasterChanges( $fname = __METHOD__ ) { |
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| 282 | |||
| 283 | /** |
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| 284 | * Commit changes on all master connections |
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| 285 | * @param string $fname Caller name |
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| 286 | * @param array $options Options map: |
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| 287 | * - maxWriteDuration: abort if more than this much time was spent in write queries |
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| 288 | * @throws Exception |
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| 289 | */ |
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| 290 | public function commitMasterChanges( $fname = __METHOD__, array $options = [] ) { |
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| 320 | |||
| 321 | /** |
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| 322 | * Rollback changes on all master connections |
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| 323 | * @param string $fname Caller name |
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| 324 | * @since 1.23 |
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| 325 | */ |
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| 326 | public function rollbackMasterChanges( $fname = __METHOD__ ) { |
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| 335 | |||
| 336 | /** |
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| 337 | * Log query info if multi DB transactions are going to be committed now |
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| 338 | */ |
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| 339 | private function logIfMultiDbTransaction() { |
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| 358 | |||
| 359 | /** |
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| 360 | * Determine if any master connection has pending changes |
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| 361 | * @return bool |
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| 362 | * @since 1.23 |
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| 363 | */ |
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| 364 | public function hasMasterChanges() { |
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| 372 | |||
| 373 | /** |
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| 374 | * Detemine if any lagged replica DB connection was used |
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| 375 | * @return bool |
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| 376 | * @since 1.28 |
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| 377 | */ |
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| 378 | public function laggedReplicaUsed() { |
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| 386 | |||
| 387 | /** |
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| 388 | * @return bool |
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| 389 | * @since 1.27 |
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| 390 | * @deprecated Since 1.28; use laggedReplicaUsed() |
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| 391 | */ |
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| 392 | public function laggedSlaveUsed() { |
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| 395 | |||
| 396 | /** |
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| 397 | * Determine if any master connection has pending/written changes from this request |
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| 398 | * @param float $age How many seconds ago is "recent" [defaults to LB lag wait timeout] |
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| 399 | * @return bool |
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| 400 | * @since 1.27 |
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| 401 | */ |
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| 402 | public function hasOrMadeRecentMasterChanges( $age = null ) { |
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| 409 | |||
| 410 | /** |
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| 411 | * Waits for the replica DBs to catch up to the current master position |
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| 412 | * |
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| 413 | * Use this when updating very large numbers of rows, as in maintenance scripts, |
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| 414 | * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs. |
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| 415 | * |
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| 416 | * By default this waits on all DB clusters actually used in this request. |
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| 417 | * This makes sense when lag being waiting on is caused by the code that does this check. |
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| 418 | * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters |
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| 419 | * that were not changed since the last wait check. To forcefully wait on a specific cluster |
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| 420 | * for a given wiki, use the 'wiki' parameter. To forcefully wait on an "external" cluster, |
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| 421 | * use the "cluster" parameter. |
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| 422 | * |
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| 423 | * Never call this function after a large DB write that is *still* in a transaction. |
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| 424 | * It only makes sense to call this after the possible lag inducing changes were committed. |
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| 425 | * |
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| 426 | * @param array $opts Optional fields that include: |
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| 427 | * - wiki : wait on the load balancer DBs that handles the given wiki |
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| 428 | * - cluster : wait on the given external load balancer DBs |
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| 429 | * - timeout : Max wait time. Default: ~60 seconds |
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| 430 | * - ifWritesSince: Only wait if writes were done since this UNIX timestamp |
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| 431 | * @throws DBReplicationWaitError If a timeout or error occured waiting on a DB cluster |
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| 432 | * @since 1.27 |
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| 433 | */ |
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| 434 | public function waitForReplication( array $opts = [] ) { |
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| 499 | |||
| 500 | /** |
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| 501 | * Add a callback to be run in every call to waitForReplication() before waiting |
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| 502 | * |
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| 503 | * Callbacks must clear any transactions that they start |
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| 504 | * |
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| 505 | * @param string $name Callback name |
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| 506 | * @param callable|null $callback Use null to unset a callback |
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| 507 | * @since 1.28 |
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| 508 | */ |
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| 509 | public function setWaitForReplicationListener( $name, callable $callback = null ) { |
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| 516 | |||
| 517 | /** |
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| 518 | * Get a token asserting that no transaction writes are active |
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| 519 | * |
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| 520 | * @param string $fname Caller name (e.g. __METHOD__) |
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| 521 | * @return mixed A value to pass to commitAndWaitForReplication() |
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| 522 | * @since 1.28 |
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| 523 | */ |
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| 524 | public function getEmptyTransactionTicket( $fname ) { |
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| 532 | |||
| 533 | /** |
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| 534 | * Convenience method for safely running commitMasterChanges()/waitForReplication() |
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| 535 | * |
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| 536 | * This will commit and wait unless $ticket indicates it is unsafe to do so |
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| 537 | * |
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| 538 | * @param string $fname Caller name (e.g. __METHOD__) |
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| 539 | * @param mixed $ticket Result of getEmptyTransactionTicket() |
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| 540 | * @param array $opts Options to waitForReplication() |
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| 541 | * @throws DBReplicationWaitError |
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| 542 | * @since 1.28 |
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| 543 | */ |
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| 544 | public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] ) { |
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| 568 | |||
| 569 | /** |
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| 570 | * @param string $dbName DB master name (e.g. "db1052") |
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| 571 | * @return float|bool UNIX timestamp when client last touched the DB or false if not recent |
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| 572 | * @since 1.28 |
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| 573 | */ |
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| 574 | public function getChronologyProtectorTouched( $dbName ) { |
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| 577 | |||
| 578 | /** |
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| 579 | * Disable the ChronologyProtector for all load balancers |
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| 580 | * |
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| 581 | * This can be called at the start of special API entry points |
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| 582 | * |
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| 583 | * @since 1.27 |
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| 584 | */ |
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| 585 | public function disableChronologyProtection() { |
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| 588 | |||
| 589 | /** |
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| 590 | * @return ChronologyProtector |
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| 591 | */ |
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| 592 | protected function newChronologyProtector() { |
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| 612 | |||
| 613 | /** |
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| 614 | * Get and record all of the staged DB positions into persistent memory storage |
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| 615 | * |
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| 616 | * @param ChronologyProtector $cp |
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| 617 | * @param callable|null $workCallback Work to do instead of waiting on syncing positions |
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| 618 | * @param string $mode One of (sync, async); whether to wait on remote datacenters |
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| 619 | */ |
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| 620 | protected function shutdownChronologyProtector( |
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| 645 | |||
| 646 | /** |
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| 647 | * @param LoadBalancer $lb |
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| 648 | */ |
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| 649 | protected function initLoadBalancer( LoadBalancer $lb ) { |
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| 654 | |||
| 655 | /** |
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| 656 | * Append ?cpPosTime parameter to a URL for ChronologyProtector purposes if needed |
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| 657 | * |
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| 658 | * Note that unlike cookies, this works accross domains |
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| 659 | * |
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| 660 | * @param string $url |
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| 661 | * @param float $time UNIX timestamp just before shutdown() was called |
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| 662 | * @return string |
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| 663 | * @since 1.28 |
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| 664 | */ |
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| 665 | public function appendPreShutdownTimeAsQuery( $url, $time ) { |
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| 677 | |||
| 678 | /** |
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| 679 | * Close all open database connections on all open load balancers. |
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| 680 | * @since 1.28 |
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| 681 | */ |
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| 682 | public function closeAll() { |
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| 685 | } |
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| 686 |
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