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