includes/libs/rdbms/loadbalancer/ILoadBalancer.php

   1 <?php
   2 /**
   3  * Database load balancing interface
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Database
  22  * @author Aaron Schulz
  23  */
  24
  25 /**
  26  * Interface for database load balancing object that manages IDatabase handles
  27  *
  28  * @since 1.28
  29  * @ingroup Database
  30  */
  31 interface ILoadBalancer {
  32         /**
  33          * Construct a manager of IDatabase connection objects
  34          *
  35          * @param array $params Parameter map with keys:
  36          *  - servers : Required. Array of server info structures.
  37          *  - localDomain: A DatabaseDomain or domain ID string.
  38          *  - loadMonitor : Name of a class used to fetch server lag and load.
  39          *  - readOnlyReason : Reason the master DB is read-only if so [optional]
  40          *  - waitTimeout : Maximum time to wait for replicas for consistency [optional]
  41          *  - srvCache : BagOStuff object for server cache [optional]
  42          *  - memCache : BagOStuff object for cluster memory cache [optional]
  43          *  - wanCache : WANObjectCache object [optional]
  44          *  - hostname : The name of the current server [optional]
  45          *  - cliMode: Whether the execution context is a CLI script. [optional]
  46          *  - profiler : Class name or instance with profileIn()/profileOut() methods. [optional]
  47          *  - trxProfiler: TransactionProfiler instance. [optional]
  48          *  - replLogger: PSR-3 logger instance. [optional]
  49          *  - connLogger: PSR-3 logger instance. [optional]
  50          *  - queryLogger: PSR-3 logger instance. [optional]
  51          *  - perfLogger: PSR-3 logger instance. [optional]
  52          *  - errorLogger : Callback that takes an Exception and logs it. [optional]
  53          * @throws InvalidArgumentException
  54          */
  55         public function __construct( array $params );
  56
  57         /**
  58          * Get the index of the reader connection, which may be a replica DB
  59          * This takes into account load ratios and lag times. It should
  60          * always return a consistent index during a given invocation
  61          *
  62          * Side effect: opens connections to databases
  63          * @param string|bool $group Query group, or false for the generic reader
  64          * @param string|bool $domain Domain ID, or false for the current domain
  65          * @throws DBError
  66          * @return bool|int|string
  67          */
  68         public function getReaderIndex( $group = false, $domain = false );
  69
  70         /**
  71          * Set the master wait position
  72          * If a DB_REPLICA connection has been opened already, waits
  73          * Otherwise sets a variable telling it to wait if such a connection is opened
  74          * @param DBMasterPos $pos
  75          */
  76         public function waitFor( $pos );
  77
  78         /**
  79          * Set the master wait position and wait for a "generic" replica DB to catch up to it
  80          *
  81          * This can be used a faster proxy for waitForAll()
  82          *
  83          * @param DBMasterPos $pos
  84          * @param int $timeout Max seconds to wait; default is mWaitTimeout
  85          * @return bool Success (able to connect and no timeouts reached)
  86          */
  87         public function waitForOne( $pos, $timeout = null );
  88
  89         /**
  90          * Set the master wait position and wait for ALL replica DBs to catch up to it
  91          * @param DBMasterPos $pos
  92          * @param int $timeout Max seconds to wait; default is mWaitTimeout
  93          * @return bool Success (able to connect and no timeouts reached)
  94          */
  95         public function waitForAll( $pos, $timeout = null );
  96
  97         /**
  98          * Get any open connection to a given server index, local or foreign
  99          * Returns false if there is no connection open
 100          *
 101          * @param int $i Server index
 102          * @return IDatabase|bool False on failure
 103          */
 104         public function getAnyOpenConnection( $i );
 105
 106         /**
 107          * Get a connection by index
 108          * This is the main entry point for this class.
 109          *
 110          * @param int $i Server index
 111          * @param array|string|bool $groups Query group(s), or false for the generic reader
 112          * @param string|bool $domain Domain ID, or false for the current domain
 113          *
 114          * @throws DBError
 115          * @return IDatabase
 116          */
 117         public function getConnection( $i, $groups = [], $domain = false );
 118
 119         /**
 120          * Mark a foreign connection as being available for reuse under a different
 121          * DB name or prefix. This mechanism is reference-counted, and must be called
 122          * the same number of times as getConnection() to work.
 123          *
 124          * @param IDatabase $conn
 125          * @throws InvalidArgumentException
 126          */
 127         public function reuseConnection( $conn );
 128
 129         /**
 130          * Get a database connection handle reference
 131          *
 132          * The handle's methods wrap simply wrap those of a IDatabase handle
 133          *
 134          * @see LoadBalancer::getConnection() for parameter information
 135          *
 136          * @param int $db
 137          * @param array|string|bool $groups Query group(s), or false for the generic reader
 138          * @param string|bool $domain Domain ID, or false for the current domain
 139          * @return DBConnRef
 140          */
 141         public function getConnectionRef( $db, $groups = [], $domain = false );
 142
 143         /**
 144          * Get a database connection handle reference without connecting yet
 145          *
 146          * The handle's methods wrap simply wrap those of a IDatabase handle
 147          *
 148          * @see LoadBalancer::getConnection() for parameter information
 149          *
 150          * @param int $db
 151          * @param array|string|bool $groups Query group(s), or false for the generic reader
 152          * @param string|bool $domain Domain ID, or false for the current domain
 153          * @return DBConnRef
 154          */
 155         public function getLazyConnectionRef( $db, $groups = [], $domain = false );
 156
 157         /**
 158          * Open a connection to the server given by the specified index
 159          * Index must be an actual index into the array.
 160          * If the server is already open, returns it.
 161          *
 162          * On error, returns false, and the connection which caused the
 163          * error will be available via $this->mErrorConnection.
 164          *
 165          * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
 166          *
 167          * @param int $i Server index
 168          * @param string|bool $domain Domain ID, or false for the current domain
 169          * @return IDatabase|bool Returns false on errors
 170          */
 171         public function openConnection( $i, $domain = false );
 172
 173         /**
 174          * @return int
 175          */
 176         public function getWriterIndex();
 177
 178         /**
 179          * Returns true if the specified index is a valid server index
 180          *
 181          * @param string $i
 182          * @return bool
 183          */
 184         public function haveIndex( $i );
 185
 186         /**
 187          * Returns true if the specified index is valid and has non-zero load
 188          *
 189          * @param string $i
 190          * @return bool
 191          */
 192         public function isNonZeroLoad( $i );
 193
 194         /**
 195          * Get the number of defined servers (not the number of open connections)
 196          *
 197          * @return int
 198          */
 199         public function getServerCount();
 200
 201         /**
 202          * Get the host name or IP address of the server with the specified index
 203          * Prefer a readable name if available.
 204          * @param string $i
 205          * @return string
 206          */
 207         public function getServerName( $i );
 208
 209         /**
 210          * Return the server info structure for a given index, or false if the index is invalid.
 211          * @param int $i
 212          * @return array|bool
 213          */
 214         public function getServerInfo( $i );
 215
 216         /**
 217          * Sets the server info structure for the given index. Entry at index $i
 218          * is created if it doesn't exist
 219          * @param int $i
 220          * @param array $serverInfo
 221          */
 222         public function setServerInfo( $i, array $serverInfo );
 223
 224         /**
 225          * Get the current master position for chronology control purposes
 226          * @return DBMasterPos|bool Returns false if not applicable
 227          */
 228         public function getMasterPos();
 229
 230         /**
 231          * Disable this load balancer. All connections are closed, and any attempt to
 232          * open a new connection will result in a DBAccessError.
 233          */
 234         public function disable();
 235
 236         /**
 237          * Close all open connections
 238          */
 239         public function closeAll();
 240
 241         /**
 242          * Close a connection
 243          *
 244          * Using this function makes sure the LoadBalancer knows the connection is closed.
 245          * If you use $conn->close() directly, the load balancer won't update its state.
 246          *
 247          * @param IDatabase $conn
 248          */
 249         public function closeConnection( IDatabase $conn );
 250
 251         /**
 252          * Commit transactions on all open connections
 253          * @param string $fname Caller name
 254          * @throws DBExpectedError
 255          */
 256         public function commitAll( $fname = __METHOD__ );
 257
 258         /**
 259          * Perform all pre-commit callbacks that remain part of the atomic transactions
 260          * and disable any post-commit callbacks until runMasterPostTrxCallbacks()
 261          *
 262          * Use this only for mutli-database commits
 263          */
 264         public function finalizeMasterChanges();
 265
 266         /**
 267          * Perform all pre-commit checks for things like replication safety
 268          *
 269          * Use this only for mutli-database commits
 270          *
 271          * @param array $options Includes:
 272          *   - maxWriteDuration : max write query duration time in seconds
 273          * @throws DBTransactionError
 274          */
 275         public function approveMasterChanges( array $options );
 276
 277         /**
 278          * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set)
 279          *
 280          * The DBO_TRX setting will be reverted to the default in each of these methods:
 281          *   - commitMasterChanges()
 282          *   - rollbackMasterChanges()
 283          *   - commitAll()
 284          * This allows for custom transaction rounds from any outer transaction scope.
 285          *
 286          * @param string $fname
 287          * @throws DBExpectedError
 288          */
 289         public function beginMasterChanges( $fname = __METHOD__ );
 290
 291         /**
 292          * Issue COMMIT on all master connections where writes where done
 293          * @param string $fname Caller name
 294          * @throws DBExpectedError
 295          */
 296         public function commitMasterChanges( $fname = __METHOD__ );
 297
 298         /**
 299          * Issue all pending post-COMMIT/ROLLBACK callbacks
 300          *
 301          * Use this only for mutli-database commits
 302          *
 303          * @param integer $type IDatabase::TRIGGER_* constant
 304          * @return Exception|null The first exception or null if there were none
 305          */
 306         public function runMasterPostTrxCallbacks( $type );
 307
 308         /**
 309          * Issue ROLLBACK only on master, only if queries were done on connection
 310          * @param string $fname Caller name
 311          * @throws DBExpectedError
 312          */
 313         public function rollbackMasterChanges( $fname = __METHOD__ );
 314
 315         /**
 316          * Suppress all pending post-COMMIT/ROLLBACK callbacks
 317          *
 318          * Use this only for mutli-database commits
 319          *
 320          * @return Exception|null The first exception or null if there were none
 321          */
 322         public function suppressTransactionEndCallbacks();
 323
 324         /**
 325          * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot
 326          *
 327          * @param string $fname Caller name
 328          */
 329         public function flushReplicaSnapshots( $fname = __METHOD__ );
 330
 331         /**
 332          * @return bool Whether a master connection is already open
 333          */
 334         public function hasMasterConnection();
 335
 336         /**
 337          * Determine if there are pending changes in a transaction by this thread
 338          * @return bool
 339          */
 340         public function hasMasterChanges();
 341
 342         /**
 343          * Get the timestamp of the latest write query done by this thread
 344          * @return float|bool UNIX timestamp or false
 345          */
 346         public function lastMasterChangeTimestamp();
 347
 348         /**
 349          * Check if this load balancer object had any recent or still
 350          * pending writes issued against it by this PHP thread
 351          *
 352          * @param float $age How many seconds ago is "recent" [defaults to mWaitTimeout]
 353          * @return bool
 354          */
 355         public function hasOrMadeRecentMasterChanges( $age = null );
 356
 357         /**
 358          * Get the list of callers that have pending master changes
 359          *
 360          * @return string[] List of method names
 361          */
 362         public function pendingMasterChangeCallers();
 363
 364         /**
 365          * @note This method will trigger a DB connection if not yet done
 366          * @param string|bool $domain Domain ID, or false for the current domain
 367          * @return bool Whether the generic connection for reads is highly "lagged"
 368          */
 369         public function getLaggedReplicaMode( $domain = false );
 370
 371         /**
 372          * @note This method will never cause a new DB connection
 373          * @return bool Whether any generic connection used for reads was highly "lagged"
 374          */
 375         public function laggedReplicaUsed();
 376
 377         /**
 378          * @note This method may trigger a DB connection if not yet done
 379          * @param string|bool $domain Domain ID, or false for the current domain
 380          * @param IDatabase|null DB master connection; used to avoid loops [optional]
 381          * @return string|bool Reason the master is read-only or false if it is not
 382          */
 383         public function getReadOnlyReason( $domain = false, IDatabase $conn = null );
 384
 385         /**
 386          * Disables/enables lag checks
 387          * @param null|bool $mode
 388          * @return bool
 389          */
 390         public function allowLagged( $mode = null );
 391
 392         /**
 393          * @return bool
 394          */
 395         public function pingAll();
 396
 397         /**
 398          * Call a function with each open connection object
 399          * @param callable $callback
 400          * @param array $params
 401          */
 402         public function forEachOpenConnection( $callback, array $params = [] );
 403
 404         /**
 405          * Call a function with each open connection object to a master
 406          * @param callable $callback
 407          * @param array $params
 408          */
 409         public function forEachOpenMasterConnection( $callback, array $params = [] );
 410
 411         /**
 412          * Call a function with each open replica DB connection object
 413          * @param callable $callback
 414          * @param array $params
 415          */
 416         public function forEachOpenReplicaConnection( $callback, array $params = [] );
 417
 418         /**
 419          * Get the hostname and lag time of the most-lagged replica DB
 420          *
 421          * This is useful for maintenance scripts that need to throttle their updates.
 422          * May attempt to open connections to replica DBs on the default DB. If there is
 423          * no lag, the maximum lag will be reported as -1.
 424          *
 425          * @param bool|string $domain Domain ID, or false for the default database
 426          * @return array ( host, max lag, index of max lagged host )
 427          */
 428         public function getMaxLag( $domain = false );
 429
 430         /**
 431          * Get an estimate of replication lag (in seconds) for each server
 432          *
 433          * Results are cached for a short time in memcached/process cache
 434          *
 435          * Values may be "false" if replication is too broken to estimate
 436          *
 437          * @param string|bool $domain
 438          * @return int[] Map of (server index => float|int|bool)
 439          */
 440         public function getLagTimes( $domain = false );
 441
 442         /**
 443          * Get the lag in seconds for a given connection, or zero if this load
 444          * balancer does not have replication enabled.
 445          *
 446          * This should be used in preference to Database::getLag() in cases where
 447          * replication may not be in use, since there is no way to determine if
 448          * replication is in use at the connection level without running
 449          * potentially restricted queries such as SHOW SLAVE STATUS. Using this
 450          * function instead of Database::getLag() avoids a fatal error in this
 451          * case on many installations.
 452          *
 453          * @param IDatabase $conn
 454          * @return int|bool Returns false on error
 455          */
 456         public function safeGetLag( IDatabase $conn );
 457
 458         /**
 459          * Wait for a replica DB to reach a specified master position
 460          *
 461          * This will connect to the master to get an accurate position if $pos is not given
 462          *
 463          * @param IDatabase $conn Replica DB
 464          * @param DBMasterPos|bool $pos Master position; default: current position
 465          * @param integer|null $timeout Timeout in seconds [optional]
 466          * @return bool Success
 467          */
 468         public function safeWaitForMasterPos( IDatabase $conn, $pos = false, $timeout = null );
 469
 470         /**
 471          * Clear the cache for slag lag delay times
 472          *
 473          * This is only used for testing
 474          */
 475         public function clearLagTimeCache();
 476
 477         /**
 478          * Set a callback via IDatabase::setTransactionListener() on
 479          * all current and future master connections of this load balancer
 480          *
 481          * @param string $name Callback name
 482          * @param callable|null $callback
 483          */
 484         public function setTransactionListener( $name, callable $callback = null );
 485
 486         /**
 487          * Set a new table prefix for the existing local domain ID for testing
 488          *
 489          * @param string $prefix
 490          */
 491         public function setDomainPrefix( $prefix );
 492
 493         /**
 494          * Make certain table names use their own database, schema, and table prefix
 495          * when passed into SQL queries pre-escaped and without a qualified database name
 496          *
 497          * For example, "user" can be converted to "myschema.mydbname.user" for convenience.
 498          * Appearances like `user`, somedb.user, somedb.someschema.user will used literally.
 499          *
 500          * Calling this twice will completely clear any old table aliases. Also, note that
 501          * callers are responsible for making sure the schemas and databases actually exist.
 502          *
 503          * @param array[] $aliases Map of (table => (dbname, schema, prefix) map)
 504          */
 505         public function setTableAliases( array $aliases );
 506 }