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