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          * This is useful for getting rid of stale data from an implicit transaction round
 184          *
 185          * @param string $fname Caller name
 186          */
 187         public function flushReplicaSnapshots( $fname = __METHOD__ );
 188
 189         /**
 190          * Commit open transactions on all connections. This is useful for two main cases:
 191          *   - a) To commit changes to the masters.
 192          *   - b) To release the snapshot on all connections, master and replica DBs.
 193          * @param string $fname Caller name
 194          * @param array $options Options map:
 195          *   - maxWriteDuration: abort if more than this much time was spent in write queries
 196          */
 197         public function commitAll( $fname = __METHOD__, array $options = [] );
 198
 199         /**
 200          * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set)
 201          *
 202          * The DBO_TRX setting will be reverted to the default in each of these methods:
 203          *   - commitMasterChanges()
 204          *   - rollbackMasterChanges()
 205          *   - commitAll()
 206          *
 207          * This allows for custom transaction rounds from any outer transaction scope.
 208          *
 209          * @param string $fname
 210          * @throws DBTransactionError
 211          */
 212         public function beginMasterChanges( $fname = __METHOD__ );
 213
 214         /**
 215          * Commit changes and clear view snapshots on all master connections
 216          * @param string $fname Caller name
 217          * @param array $options Options map:
 218          *   - maxWriteDuration: abort if more than this much time was spent in write queries
 219          * @throws DBTransactionError
 220          */
 221         public function commitMasterChanges( $fname = __METHOD__, array $options = [] );
 222
 223         /**
 224          * Rollback changes on all master connections
 225          * @param string $fname Caller name
 226          */
 227         public function rollbackMasterChanges( $fname = __METHOD__ );
 228
 229         /**
 230          * Check if an explicit transaction round is active
 231          * @return bool
 232          * @since 1.29
 233          */
 234         public function hasTransactionRound();
 235
 236         /**
 237          * Check if transaction rounds can be started, committed, or rolled back right now
 238          *
 239          * This can be used as a recusion guard to avoid exceptions in transaction callbacks
 240          *
 241          * @return bool
 242          * @since 1.32
 243          */
 244         public function isReadyForRoundOperations();
 245
 246         /**
 247          * Determine if any master connection has pending changes
 248          * @return bool
 249          */
 250         public function hasMasterChanges();
 251
 252         /**
 253          * Detemine if any lagged replica DB connection was used
 254          * @return bool
 255          */
 256         public function laggedReplicaUsed();
 257
 258         /**
 259          * Determine if any master connection has pending/written changes from this request
 260          * @param float|null $age How many seconds ago is "recent" [defaults to LB lag wait timeout]
 261          * @return bool
 262          */
 263         public function hasOrMadeRecentMasterChanges( $age = null );
 264
 265         /**
 266          * Waits for the replica DBs to catch up to the current master position
 267          *
 268          * Use this when updating very large numbers of rows, as in maintenance scripts,
 269          * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs.
 270          *
 271          * By default this waits on all DB clusters actually used in this request.
 272          * This makes sense when lag being waiting on is caused by the code that does this check.
 273          * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
 274          * that were not changed since the last wait check. To forcefully wait on a specific cluster
 275          * for a given domain, use the 'domain' parameter. To forcefully wait on an "external" cluster,
 276          * use the "cluster" parameter.
 277          *
 278          * Never call this function after a large DB write that is *still* in a transaction.
 279          * It only makes sense to call this after the possible lag inducing changes were committed.
 280          *
 281          * @param array $opts Optional fields that include:
 282          *   - domain : wait on the load balancer DBs that handles the given domain ID
 283          *   - cluster : wait on the given external load balancer DBs
 284          *   - timeout : Max wait time. Default: 60 seconds for CLI, 1 second for web.
 285          *   - ifWritesSince: Only wait if writes were done since this UNIX timestamp
 286          * @return bool True on success, false if a timeout or error occurred while waiting
 287          */
 288         public function waitForReplication( array $opts = [] );
 289
 290         /**
 291          * Add a callback to be run in every call to waitForReplication() before waiting
 292          *
 293          * Callbacks must clear any transactions that they start
 294          *
 295          * @param string $name Callback name
 296          * @param callable|null $callback Use null to unset a callback
 297          */
 298         public function setWaitForReplicationListener( $name, callable $callback = null );
 299
 300         /**
 301          * Get a token asserting that no transaction writes are active
 302          *
 303          * @param string $fname Caller name (e.g. __METHOD__)
 304          * @return mixed A value to pass to commitAndWaitForReplication()
 305          */
 306         public function getEmptyTransactionTicket( $fname );
 307
 308         /**
 309          * Convenience method for safely running commitMasterChanges()/waitForReplication()
 310          *
 311          * This will commit and wait unless $ticket indicates it is unsafe to do so
 312          *
 313          * @param string $fname Caller name (e.g. __METHOD__)
 314          * @param mixed $ticket Result of getEmptyTransactionTicket()
 315          * @param array $opts Options to waitForReplication()
 316          * @return bool True if the wait was successful, false on timeout
 317          */
 318         public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] );
 319
 320         /**
 321          * @param string $dbName DB master name (e.g. "db1052")
 322          * @return float|bool UNIX timestamp when client last touched the DB or false if not recent
 323          */
 324         public function getChronologyProtectorTouched( $dbName );
 325
 326         /**
 327          * Disable the ChronologyProtector for all load balancers
 328          *
 329          * This can be called at the start of special API entry points
 330          */
 331         public function disableChronologyProtection();
 332
 333         /**
 334          * Set a new table prefix for the existing local domain ID for testing
 335          *
 336          * @param string $prefix
 337          * @since 1.33
 338          */
 339         public function setLocalDomainPrefix( $prefix );
 340
 341         /**
 342          * Close all open database connections on all open load balancers.
 343          */
 344         public function closeAll();
 345
 346         /**
 347          * @param string $agent Agent name for query profiling
 348          */
 349         public function setAgentName( $agent );
 350
 351         /**
 352          * Append ?cpPosIndex parameter to a URL for ChronologyProtector purposes if needed
 353          *
 354          * Note that unlike cookies, this works across domains
 355          *
 356          * @param string $url
 357          * @param int $index Write counter index
 358          * @return string
 359          */
 360         public function appendShutdownCPIndexAsQuery( $url, $index );
 361
 362         /**
 363          * Get the client ID of the ChronologyProtector instance
 364          *
 365          * @return string Client ID
 366          * @since 1.34
 367          */
 368         public function getChronologyProtectorClientId();
 369
 370         /**
 371          * @param array $info Map of fields, including:
 372          *   - IPAddress : IP address
 373          *   - UserAgent : User-Agent HTTP header
 374          *   - ChronologyProtection : cookie/header value specifying ChronologyProtector usage
 375          *   - ChronologyPositionIndex: timestamp used to get up-to-date DB positions for the agent
 376          */
 377         public function setRequestInfo( array $info );
 378
 379         /**
 380          * Make certain table names use their own database, schema, and table prefix
 381          * when passed into SQL queries pre-escaped and without a qualified database name
 382          *
 383          * For example, "user" can be converted to "myschema.mydbname.user" for convenience.
 384          * Appearances like `user`, somedb.user, somedb.someschema.user will used literally.
 385          *
 386          * Calling this twice will completely clear any old table aliases. Also, note that
 387          * callers are responsible for making sure the schemas and databases actually exist.
 388          *
 389          * @param array[] $aliases Map of (table => (dbname, schema, prefix) map)
 390          * @since 1.31
 391          */
 392         public function setTableAliases( array $aliases );
 393
 394         /**
 395          * Convert certain index names to alternative names before querying the DB
 396          *
 397          * Note that this applies to indexes regardless of the table they belong to.
 398          *
 399          * This can be employed when an index was renamed X => Y in code, but the new Y-named
 400          * indexes were not yet built on all DBs. After all the Y-named ones are added by the DBA,
 401          * the aliases can be removed, and then the old X-named indexes dropped.
 402          *
 403          * @param string[] $aliases
 404          * @since 1.31
 405          */
 406         public function setIndexAliases( array $aliases );
 407 }