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         /** @var int Don't save DB positions at all */
  35         const SHUTDOWN_NO_CHRONPROT = 0; // don't save DB positions at all
  36         /** @var int Save DB positions, but don't wait on remote DCs */
  37         const SHUTDOWN_CHRONPROT_ASYNC = 1;
  38         /** @var int Save DB positions, waiting on all DCs */
  39         const SHUTDOWN_CHRONPROT_SYNC = 2;
  40
  41         /** @var string Default main LB cluster name (do not change this) */
  42         const CLUSTER_MAIN_DEFAULT = 'DEFAULT';
  43
  44         /**
  45          * Construct a manager of ILoadBalancer objects
  46          *
  47          * Sub-classes will extend the required keys in $conf with additional parameters
  48          *
  49          * @param array $conf Array with keys:
  50          *  - localDomain: A DatabaseDomain or domain ID string.
  51          *  - readOnlyReason: Reason the master DB is read-only if so [optional]
  52          *  - srvCache: BagOStuff object for server cache [optional]
  53          *  - memStash: BagOStuff object for cross-datacenter memory storage [optional]
  54          *  - wanCache: WANObjectCache object [optional]
  55          *  - hostname: The name of the current server [optional]
  56          *  - cliMode: Whether the execution context is a CLI script. [optional]
  57          *  - maxLag: Try to avoid DB replicas with lag above this many seconds [optional]
  58          *  - profiler: Class name or instance with profileIn()/profileOut() methods. [optional]
  59          *  - trxProfiler: TransactionProfiler instance. [optional]
  60          *  - replLogger: PSR-3 logger instance. [optional]
  61          *  - connLogger: PSR-3 logger instance. [optional]
  62          *  - queryLogger: PSR-3 logger instance. [optional]
  63          *  - perfLogger: PSR-3 logger instance. [optional]
  64          *  - errorLogger: Callback that takes an Exception and logs it. [optional]
  65          *  - deprecationLogger: Callback to log a deprecation warning. [optional]
  66          *  - secret: Secret string to use for HMAC hashing [optional]
  67          * @throws InvalidArgumentException
  68          */
  69         public function __construct( array $conf );
  70
  71         /**
  72          * Disables all load balancers. All connections are closed, and any attempt to
  73          * open a new connection will result in a DBAccessError.
  74          * @see ILoadBalancer::disable()
  75          */
  76         public function destroy();
  77
  78         /**
  79          * Get the local (and default) database domain ID of connection handles
  80          *
  81          * @see DatabaseDomain
  82          * @return string Database domain ID; this specifies DB name, schema, and table prefix
  83          * @since 1.32
  84          */
  85         public function getLocalDomainID();
  86
  87         /**
  88          * @param DatabaseDomain|string|bool $domain Database domain
  89          * @return string Value of $domain if provided or the local domain otherwise
  90          * @since 1.32
  91          */
  92         public function resolveDomainID( $domain );
  93
  94         /**
  95          * Close all connection and redefine the local domain for testing or schema creation
  96          *
  97          * @param DatabaseDomain|string $domain
  98          * @since 1.33
  99          */
 100         public function redefineLocalDomain( $domain );
 101
 102         /**
 103          * Create a new load balancer object. The resulting object will be untracked,
 104          * not chronology-protected, and the caller is responsible for cleaning it up.
 105          *
 106          * This method is for only advanced usage and callers should almost always use
 107          * getMainLB() instead. This method can be useful when a table is used as a key/value
 108          * store. In that cases, one might want to query it in autocommit mode (DBO_TRX off)
 109          * but still use DBO_TRX transaction rounds on other tables.
 110          *
 111          * @param bool|string $domain Domain ID, or false for the current domain
 112          * @return ILoadBalancer
 113          */
 114         public function newMainLB( $domain = false );
 115
 116         /**
 117          * Get a cached (tracked) load balancer object.
 118          *
 119          * @param bool|string $domain Domain ID, or false for the current domain
 120          * @return ILoadBalancer
 121          */
 122         public function getMainLB( $domain = false );
 123
 124         /**
 125          * Create a new load balancer for external storage. The resulting object will be
 126          * untracked, not chronology-protected, and the caller is responsible for cleaning it up.
 127          *
 128          * This method is for only advanced usage and callers should almost always use
 129          * getExternalLB() instead. This method can be useful when a table is used as a
 130          * key/value store. In that cases, one might want to query it in autocommit mode
 131          * (DBO_TRX off) but still use DBO_TRX transaction rounds on other tables.
 132          *
 133          * @param string $cluster External storage cluster name
 134          * @return ILoadBalancer
 135          */
 136         public function newExternalLB( $cluster );
 137
 138         /**
 139          * Get a cached (tracked) load balancer for external storage
 140          *
 141          * @param string $cluster External storage cluster name
 142          * @return ILoadBalancer
 143          */
 144         public function getExternalLB( $cluster );
 145
 146         /**
 147          * Get cached (tracked) load balancers for all main database clusters
 148          *
 149          * The default cluster name is ILoadBalancer::CLUSTER_MAIN_DEFAULT
 150          *
 151          * @return ILoadBalancer[] Map of (cluster name => ILoadBalancer)
 152          * @since 1.29
 153          */
 154         public function getAllMainLBs();
 155
 156         /**
 157          * Get cached (tracked) load balancers for all external database clusters
 158          *
 159          * @return ILoadBalancer[] Map of (cluster name => ILoadBalancer)
 160          * @since 1.29
 161          */
 162         public function getAllExternalLBs();
 163
 164         /**
 165          * Execute a function for each currently tracked (instantiated) load balancer
 166          *
 167          * The callback is called with the load balancer as the first parameter,
 168          * and $params passed as the subsequent parameters.
 169          *
 170          * @param callable $callback
 171          * @param array $params
 172          */
 173         public function forEachLB( $callback, array $params = [] );
 174
 175         /**
 176          * Prepare all currently tracked (instantiated) load balancers for shutdown
 177          *
 178          * @param int $mode One of the class SHUTDOWN_* constants
 179          * @param callable|null $workCallback Work to mask ChronologyProtector writes
 180          * @param int|null &$cpIndex Position key write counter for ChronologyProtector
 181          * @param string|null &$cpClientId Client ID hash for ChronologyProtector
 182          */
 183         public function shutdown(
 184                 $mode = self::SHUTDOWN_CHRONPROT_SYNC,
 185                 callable $workCallback = null,
 186                 &$cpIndex = null,
 187                 &$cpClientId = null
 188         );
 189
 190         /**
 191          * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot
 192          *
 193          * This is useful for getting rid of stale data from an implicit transaction round
 194          *
 195          * @param string $fname Caller name
 196          */
 197         public function flushReplicaSnapshots( $fname = __METHOD__ );
 198
 199         /**
 200          * Commit open transactions on all connections. This is useful for two main cases:
 201          *   - a) To commit changes to the masters.
 202          *   - b) To release the snapshot on all connections, master and replica DBs.
 203          * @param string $fname Caller name
 204          * @param array $options Options map:
 205          *   - maxWriteDuration: abort if more than this much time was spent in write queries
 206          */
 207         public function commitAll( $fname = __METHOD__, array $options = [] );
 208
 209         /**
 210          * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set)
 211          *
 212          * The DBO_TRX setting will be reverted to the default in each of these methods:
 213          *   - commitMasterChanges()
 214          *   - rollbackMasterChanges()
 215          *   - commitAll()
 216          *
 217          * This allows for custom transaction rounds from any outer transaction scope.
 218          *
 219          * @param string $fname
 220          * @throws DBTransactionError
 221          */
 222         public function beginMasterChanges( $fname = __METHOD__ );
 223
 224         /**
 225          * Commit changes and clear view snapshots on all master connections
 226          * @param string $fname Caller name
 227          * @param array $options Options map:
 228          *   - maxWriteDuration: abort if more than this much time was spent in write queries
 229          * @throws DBTransactionError
 230          */
 231         public function commitMasterChanges( $fname = __METHOD__, array $options = [] );
 232
 233         /**
 234          * Rollback changes on all master connections
 235          * @param string $fname Caller name
 236          */
 237         public function rollbackMasterChanges( $fname = __METHOD__ );
 238
 239         /**
 240          * Check if an explicit transaction round is active
 241          * @return bool
 242          * @since 1.29
 243          */
 244         public function hasTransactionRound();
 245
 246         /**
 247          * Check if transaction rounds can be started, committed, or rolled back right now
 248          *
 249          * This can be used as a recusion guard to avoid exceptions in transaction callbacks
 250          *
 251          * @return bool
 252          * @since 1.32
 253          */
 254         public function isReadyForRoundOperations();
 255
 256         /**
 257          * Determine if any master connection has pending changes
 258          * @return bool
 259          */
 260         public function hasMasterChanges();
 261
 262         /**
 263          * Detemine if any lagged replica DB connection was used
 264          * @return bool
 265          */
 266         public function laggedReplicaUsed();
 267
 268         /**
 269          * Determine if any master connection has pending/written changes from this request
 270          * @param float|null $age How many seconds ago is "recent" [defaults to LB lag wait timeout]
 271          * @return bool
 272          */
 273         public function hasOrMadeRecentMasterChanges( $age = null );
 274
 275         /**
 276          * Waits for the replica DBs to catch up to the current master position
 277          *
 278          * Use this when updating very large numbers of rows, as in maintenance scripts,
 279          * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs.
 280          *
 281          * By default this waits on all DB clusters actually used in this request.
 282          * This makes sense when lag being waiting on is caused by the code that does this check.
 283          * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
 284          * that were not changed since the last wait check. To forcefully wait on a specific cluster
 285          * for a given domain, use the 'domain' parameter. To forcefully wait on an "external" cluster,
 286          * use the "cluster" parameter.
 287          *
 288          * Never call this function after a large DB write that is *still* in a transaction.
 289          * It only makes sense to call this after the possible lag inducing changes were committed.
 290          *
 291          * @param array $opts Optional fields that include:
 292          *   - domain : wait on the load balancer DBs that handles the given domain ID
 293          *   - cluster : wait on the given external load balancer DBs
 294          *   - timeout : Max wait time. Default: 60 seconds for CLI, 1 second for web.
 295          *   - ifWritesSince: Only wait if writes were done since this UNIX timestamp
 296          * @return bool True on success, false if a timeout or error occurred while waiting
 297          */
 298         public function waitForReplication( array $opts = [] );
 299
 300         /**
 301          * Add a callback to be run in every call to waitForReplication() before waiting
 302          *
 303          * Callbacks must clear any transactions that they start
 304          *
 305          * @param string $name Callback name
 306          * @param callable|null $callback Use null to unset a callback
 307          */
 308         public function setWaitForReplicationListener( $name, callable $callback = null );
 309
 310         /**
 311          * Get a token asserting that no transaction writes are active
 312          *
 313          * @param string $fname Caller name (e.g. __METHOD__)
 314          * @return mixed A value to pass to commitAndWaitForReplication()
 315          */
 316         public function getEmptyTransactionTicket( $fname );
 317
 318         /**
 319          * Convenience method for safely running commitMasterChanges()/waitForReplication()
 320          *
 321          * This will commit and wait unless $ticket indicates it is unsafe to do so
 322          *
 323          * @param string $fname Caller name (e.g. __METHOD__)
 324          * @param mixed $ticket Result of getEmptyTransactionTicket()
 325          * @param array $opts Options to waitForReplication()
 326          * @return bool True if the wait was successful, false on timeout
 327          */
 328         public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] );
 329
 330         /**
 331          * @param string $dbName DB master name (e.g. "db1052")
 332          * @return float|bool UNIX timestamp when client last touched the DB or false if not recent
 333          */
 334         public function getChronologyProtectorTouched( $dbName );
 335
 336         /**
 337          * Disable the ChronologyProtector for all load balancers
 338          *
 339          * This can be called at the start of special API entry points
 340          */
 341         public function disableChronologyProtection();
 342
 343         /**
 344          * Set a new table prefix for the existing local domain ID for testing
 345          *
 346          * @param string $prefix
 347          * @since 1.33
 348          */
 349         public function setLocalDomainPrefix( $prefix );
 350
 351         /**
 352          * Close all open database connections on all open load balancers.
 353          */
 354         public function closeAll();
 355
 356         /**
 357          * @param string $agent Agent name for query profiling
 358          */
 359         public function setAgentName( $agent );
 360
 361         /**
 362          * Append ?cpPosIndex parameter to a URL for ChronologyProtector purposes if needed
 363          *
 364          * Note that unlike cookies, this works across domains
 365          *
 366          * @param string $url
 367          * @param int $index Write counter index
 368          * @return string
 369          */
 370         public function appendShutdownCPIndexAsQuery( $url, $index );
 371
 372         /**
 373          * Get the client ID of the ChronologyProtector instance
 374          *
 375          * @return string Client ID
 376          * @since 1.34
 377          */
 378         public function getChronologyProtectorClientId();
 379
 380         /**
 381          * @param array $info Map of fields, including:
 382          *   - IPAddress : IP address
 383          *   - UserAgent : User-Agent HTTP header
 384          *   - ChronologyProtection : cookie/header value specifying ChronologyProtector usage
 385          *   - ChronologyPositionIndex: timestamp used to get up-to-date DB positions for the agent
 386          */
 387         public function setRequestInfo( array $info );
 388
 389         /**
 390          * Make certain table names use their own database, schema, and table prefix
 391          * when passed into SQL queries pre-escaped and without a qualified database name
 392          *
 393          * For example, "user" can be converted to "myschema.mydbname.user" for convenience.
 394          * Appearances like `user`, somedb.user, somedb.someschema.user will used literally.
 395          *
 396          * Calling this twice will completely clear any old table aliases. Also, note that
 397          * callers are responsible for making sure the schemas and databases actually exist.
 398          *
 399          * @param array[] $aliases Map of (table => (dbname, schema, prefix) map)
 400          * @since 1.31
 401          */
 402         public function setTableAliases( array $aliases );
 403
 404         /**
 405          * Convert certain index names to alternative names before querying the DB
 406          *
 407          * Note that this applies to indexes regardless of the table they belong to.
 408          *
 409          * This can be employed when an index was renamed X => Y in code, but the new Y-named
 410          * indexes were not yet built on all DBs. After all the Y-named ones are added by the DBA,
 411          * the aliases can be removed, and then the old X-named indexes dropped.
 412          *
 413          * @param string[] $aliases
 414          * @since 1.31
 415          */
 416         public function setIndexAliases( array $aliases );
 417 }