includes/libs/rdbms/lbfactory/ILBFactory.php

   1 <?php
   2 /**
   3  * Generator and manager of database load balancing objects
   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  */
  23
  24 namespace Wikimedia\Rdbms;
  25
  26 use InvalidArgumentException;
  27
  28 /**
  29  * An interface for generating database load balancers
  30  * @ingroup Database
  31  * @since 1.28
  32  */
  33 interface ILBFactory {
  34         const SHUTDOWN_NO_CHRONPROT = 0; // don't save DB positions at all
  35         const SHUTDOWN_CHRONPROT_ASYNC = 1; // save DB positions, but don't wait on remote DCs
  36         const SHUTDOWN_CHRONPROT_SYNC = 2; // save DB positions, waiting on all DCs
  37
  38         /**
  39          * Construct a manager of ILoadBalancer objects
  40          *
  41          * Sub-classes will extend the required keys in $conf with additional parameters
  42          *
  43          * @param array $conf Array with keys:
  44          *  - localDomain: A DatabaseDomain or domain ID string.
  45          *  - readOnlyReason: Reason the master DB is read-only if so [optional]
  46          *  - srvCache: BagOStuff object for server cache [optional]
  47          *  - memStash: BagOStuff object for cross-datacenter memory storage [optional]
  48          *  - wanCache: WANObjectCache object [optional]
  49          *  - hostname: The name of the current server [optional]
  50          *  - cliMode: Whether the execution context is a CLI script. [optional]
  51          *  - maxLag: Try to avoid DB replicas with lag above this many seconds [optional]
  52          *  - profiler: Class name or instance with profileIn()/profileOut() methods. [optional]
  53          *  - trxProfiler: TransactionProfiler instance. [optional]
  54          *  - replLogger: PSR-3 logger instance. [optional]
  55          *  - connLogger: PSR-3 logger instance. [optional]
  56          *  - queryLogger: PSR-3 logger instance. [optional]
  57          *  - perfLogger: PSR-3 logger instance. [optional]
  58          *  - errorLogger: Callback that takes an Exception and logs it. [optional]
  59          *  - deprecationLogger: Callback to log a deprecation warning. [optional]
  60          *  - secret: Secret string to use for HMAC hashing [optional]
  61          * @throws InvalidArgumentException
  62          */
  63         public function __construct( array $conf );
  64
  65         /**
  66          * Disables all load balancers. All connections are closed, and any attempt to
  67          * open a new connection will result in a DBAccessError.
  68          * @see ILoadBalancer::disable()
  69          */
  70         public function destroy();
  71
  72         /**
  73          * Get the local (and default) database domain ID of connection handles
  74          *
  75          * @see DatabaseDomain
  76          * @return string Database domain ID; this specifies DB name, schema, and table prefix
  77          * @since 1.32
  78          */
  79         public function getLocalDomainID();
  80
  81         /**
  82          * @param DatabaseDomain|string|bool $domain Database domain
  83          * @return string Value of $domain if provided or the local domain otherwise
  84          * @since 1.32
  85          */
  86         public function resolveDomainID( $domain );
  87
  88         /**
  89          * Close all connection and redefine the local domain for testing or schema creation
  90          *
  91          * @param DatabaseDomain|string $domain
  92          * @since 1.33
  93          */
  94         public function redefineLocalDomain( $domain );
  95
  96         /**
  97          * Create a new load balancer object. The resulting object will be untracked,
  98          * not chronology-protected, and the caller is responsible for cleaning it up.
  99          *
 100          * This method is for only advanced usage and callers should almost always use
 101          * getMainLB() instead. This method can be useful when a table is used as a key/value
 102          * store. In that cases, one might want to query it in autocommit mode (DBO_TRX off)
 103          * but still use DBO_TRX transaction rounds on other tables.
 104          *
 105          * @param bool|string $domain Domain ID, or false for the current domain
 106          * @return ILoadBalancer
 107          */
 108         public function newMainLB( $domain = false );
 109
 110         /**
 111          * Get a cached (tracked) load balancer object.
 112          *
 113          * @param bool|string $domain Domain ID, or false for the current domain
 114          * @return ILoadBalancer
 115          */
 116         public function getMainLB( $domain = false );
 117
 118         /**
 119          * Create a new load balancer for external storage. The resulting object will be
 120          * untracked, not chronology-protected, and the caller is responsible for cleaning it up.
 121          *
 122          * This method is for only advanced usage and callers should almost always use
 123          * getExternalLB() instead. This method can be useful when a table is used as a
 124          * key/value store. In that cases, one might want to query it in autocommit mode
 125          * (DBO_TRX off) but still use DBO_TRX transaction rounds on other tables.
 126          *
 127          * @param string $cluster External storage cluster name
 128          * @return ILoadBalancer
 129          */
 130         public function newExternalLB( $cluster );
 131
 132         /**
 133          * Get a cached (tracked) load balancer for external storage
 134          *
 135          * @param string $cluster External storage cluster name
 136          * @return ILoadBalancer
 137          */
 138         public function getExternalLB( $cluster );
 139
 140         /**
 141          * Get cached (tracked) load balancers for all main database clusters
 142          *
 143          * @return ILoadBalancer[] Map of (cluster name => ILoadBalancer)
 144          * @since 1.29
 145          */
 146         public function getAllMainLBs();
 147
 148         /**
 149          * Get cached (tracked) load balancers for all external database clusters
 150          *
 151          * @return ILoadBalancer[] Map of (cluster name => ILoadBalancer)
 152          * @since 1.29
 153          */
 154         public function getAllExternalLBs();
 155
 156         /**
 157          * Execute a function for each tracked load balancer
 158          * The callback is called with the load balancer as the first parameter,
 159          * and $params passed as the subsequent parameters.
 160          *
 161          * @param callable $callback
 162          * @param array $params
 163          */
 164         public function forEachLB( $callback, array $params = [] );
 165
 166         /**
 167          * Prepare all tracked load balancers for shutdown
 168          * @param int $mode One of the class SHUTDOWN_* constants
 169          * @param callable|null $workCallback Work to mask ChronologyProtector writes
 170          * @param int|null &$cpIndex Position key write counter for ChronologyProtector
 171          * @param string|null &$cpClientId Client ID hash for ChronologyProtector
 172          */
 173         public function shutdown(
 174                 $mode = self::SHUTDOWN_CHRONPROT_SYNC,
 175                 callable $workCallback = null,
 176                 &$cpIndex = null,
 177                 &$cpClientId = null
 178         );
 179
 180         /**
 181          * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot
 182          *
 183          * @param string $fname Caller name
 184          */
 185         public function flushReplicaSnapshots( $fname = __METHOD__ );
 186
 187         /**
 188          * Commit open transactions on all connections. This is useful for two main cases:
 189          *   - a) To commit changes to the masters.
 190          *   - b) To release the snapshot on all connections, master and replica DBs.
 191          * @param string $fname Caller name
 192          * @param array $options Options map:
 193          *   - maxWriteDuration: abort if more than this much time was spent in write queries
 194          */
 195         public function commitAll( $fname = __METHOD__, array $options = [] );
 196
 197         /**
 198          * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set)
 199          *
 200          * The DBO_TRX setting will be reverted to the default in each of these methods:
 201          *   - commitMasterChanges()
 202          *   - rollbackMasterChanges()
 203          *   - commitAll()
 204          *
 205          * This allows for custom transaction rounds from any outer transaction scope.
 206          *
 207          * @param string $fname
 208          * @throws DBTransactionError
 209          */
 210         public function beginMasterChanges( $fname = __METHOD__ );
 211
 212         /**
 213          * Commit changes and clear view snapshots on all master connections
 214          * @param string $fname Caller name
 215          * @param array $options Options map:
 216          *   - maxWriteDuration: abort if more than this much time was spent in write queries
 217          * @throws DBTransactionError
 218          */
 219         public function commitMasterChanges( $fname = __METHOD__, array $options = [] );
 220
 221         /**
 222          * Rollback changes on all master connections
 223          * @param string $fname Caller name
 224          */
 225         public function rollbackMasterChanges( $fname = __METHOD__ );
 226
 227         /**
 228          * Check if an explicit transaction round is active
 229          * @return bool
 230          * @since 1.29
 231          */
 232         public function hasTransactionRound();
 233
 234         /**
 235          * Check if transaction rounds can be started, committed, or rolled back right now
 236          *
 237          * This can be used as a recusion guard to avoid exceptions in transaction callbacks
 238          *
 239          * @return bool
 240          * @since 1.32
 241          */
 242         public function isReadyForRoundOperations();
 243
 244         /**
 245          * Determine if any master connection has pending changes
 246          * @return bool
 247          */
 248         public function hasMasterChanges();
 249
 250         /**
 251          * Detemine if any lagged replica DB connection was used
 252          * @return bool
 253          */
 254         public function laggedReplicaUsed();
 255
 256         /**
 257          * Determine if any master connection has pending/written changes from this request
 258          * @param float|null $age How many seconds ago is "recent" [defaults to LB lag wait timeout]
 259          * @return bool
 260          */
 261         public function hasOrMadeRecentMasterChanges( $age = null );
 262
 263         /**
 264          * Waits for the replica DBs to catch up to the current master position
 265          *
 266          * Use this when updating very large numbers of rows, as in maintenance scripts,
 267          * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs.
 268          *
 269          * By default this waits on all DB clusters actually used in this request.
 270          * This makes sense when lag being waiting on is caused by the code that does this check.
 271          * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
 272          * that were not changed since the last wait check. To forcefully wait on a specific cluster
 273          * for a given domain, use the 'domain' parameter. To forcefully wait on an "external" cluster,
 274          * use the "cluster" parameter.
 275          *
 276          * Never call this function after a large DB write that is *still* in a transaction.
 277          * It only makes sense to call this after the possible lag inducing changes were committed.
 278          *
 279          * @param array $opts Optional fields that include:
 280          *   - domain : wait on the load balancer DBs that handles the given domain ID
 281          *   - cluster : wait on the given external load balancer DBs
 282          *   - timeout : Max wait time. Default: 60 seconds for CLI, 1 second for web.
 283          *   - ifWritesSince: Only wait if writes were done since this UNIX timestamp
 284          * @return bool True on success, false if a timeout or error occurred while waiting
 285          */
 286         public function waitForReplication( array $opts = [] );
 287
 288         /**
 289          * Add a callback to be run in every call to waitForReplication() before waiting
 290          *
 291          * Callbacks must clear any transactions that they start
 292          *
 293          * @param string $name Callback name
 294          * @param callable|null $callback Use null to unset a callback
 295          */
 296         public function setWaitForReplicationListener( $name, callable $callback = null );
 297
 298         /**
 299          * Get a token asserting that no transaction writes are active
 300          *
 301          * @param string $fname Caller name (e.g. __METHOD__)
 302          * @return mixed A value to pass to commitAndWaitForReplication()
 303          */
 304         public function getEmptyTransactionTicket( $fname );
 305
 306         /**
 307          * Convenience method for safely running commitMasterChanges()/waitForReplication()
 308          *
 309          * This will commit and wait unless $ticket indicates it is unsafe to do so
 310          *
 311          * @param string $fname Caller name (e.g. __METHOD__)
 312          * @param mixed $ticket Result of getEmptyTransactionTicket()
 313          * @param array $opts Options to waitForReplication()
 314          * @return bool True if the wait was successful, false on timeout
 315          */
 316         public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] );
 317
 318         /**
 319          * @param string $dbName DB master name (e.g. "db1052")
 320          * @return float|bool UNIX timestamp when client last touched the DB or false if not recent
 321          */
 322         public function getChronologyProtectorTouched( $dbName );
 323
 324         /**
 325          * Disable the ChronologyProtector for all load balancers
 326          *
 327          * This can be called at the start of special API entry points
 328          */
 329         public function disableChronologyProtection();
 330
 331         /**
 332          * Set a new table prefix for the existing local domain ID for testing
 333          *
 334          * @param string $prefix
 335          * @since 1.33
 336          */
 337         public function setLocalDomainPrefix( $prefix );
 338
 339         /**
 340          * Close all open database connections on all open load balancers.
 341          */
 342         public function closeAll();
 343
 344         /**
 345          * @param string $agent Agent name for query profiling
 346          */
 347         public function setAgentName( $agent );
 348
 349         /**
 350          * Append ?cpPosIndex parameter to a URL for ChronologyProtector purposes if needed
 351          *
 352          * Note that unlike cookies, this works across domains
 353          *
 354          * @param string $url
 355          * @param int $index Write counter index
 356          * @return string
 357          */
 358         public function appendShutdownCPIndexAsQuery( $url, $index );
 359
 360         /**
 361          * Get the client ID of the ChronologyProtector instance
 362          *
 363          * @return string Client ID
 364          * @since 1.34
 365          */
 366         public function getChronologyProtectorClientId();
 367
 368         /**
 369          * @param array $info Map of fields, including:
 370          *   - IPAddress : IP address
 371          *   - UserAgent : User-Agent HTTP header
 372          *   - ChronologyProtection : cookie/header value specifying ChronologyProtector usage
 373          *   - ChronologyPositionIndex: timestamp used to get up-to-date DB positions for the agent
 374          */
 375         public function setRequestInfo( array $info );
 376
 377         /**
 378          * Make certain table names use their own database, schema, and table prefix
 379          * when passed into SQL queries pre-escaped and without a qualified database name
 380          *
 381          * For example, "user" can be converted to "myschema.mydbname.user" for convenience.
 382          * Appearances like `user`, somedb.user, somedb.someschema.user will used literally.
 383          *
 384          * Calling this twice will completely clear any old table aliases. Also, note that
 385          * callers are responsible for making sure the schemas and databases actually exist.
 386          *
 387          * @param array[] $aliases Map of (table => (dbname, schema, prefix) map)
 388          * @since 1.31
 389          */
 390         public function setTableAliases( array $aliases );
 391
 392         /**
 393          * Convert certain index names to alternative names before querying the DB
 394          *
 395          * Note that this applies to indexes regardless of the table they belong to.
 396          *
 397          * This can be employed when an index was renamed X => Y in code, but the new Y-named
 398          * indexes were not yet built on all DBs. After all the Y-named ones are added by the DBA,
 399          * the aliases can be removed, and then the old X-named indexes dropped.
 400          *
 401          * @param string[] $aliases
 402          * @since 1.31
 403          */
 404         public function setIndexAliases( array $aliases );
 405 }