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 /**
  25  * An interface for generating database load balancers
  26  * @ingroup Database
  27  * @since 1.28
  28  */
  29 interface ILBFactory {
  30         const SHUTDOWN_NO_CHRONPROT = 0; // don't save DB positions at all
  31         const SHUTDOWN_CHRONPROT_ASYNC = 1; // save DB positions, but don't wait on remote DCs
  32         const SHUTDOWN_CHRONPROT_SYNC = 2; // save DB positions, waiting on all DCs
  33
  34         /**
  35          * Construct a manager of ILoadBalancer objects
  36          *
  37          * Sub-classes will extend the required keys in $conf with additional parameters
  38          *
  39          * @param $conf $params Array with keys:
  40          *  - localDomain: A DatabaseDomain or domain ID string.
  41          *  - readOnlyReason : Reason the master DB is read-only if so [optional]
  42          *  - srvCache : BagOStuff object for server cache [optional]
  43          *  - memCache : BagOStuff object for cluster memory cache [optional]
  44          *  - wanCache : WANObjectCache object [optional]
  45          *  - hostname : The name of the current server [optional]
  46          *  - cliMode: Whether the execution context is a CLI script. [optional]
  47          *  - profiler : Class name or instance with profileIn()/profileOut() methods. [optional]
  48          *  - trxProfiler: TransactionProfiler instance. [optional]
  49          *  - replLogger: PSR-3 logger instance. [optional]
  50          *  - connLogger: PSR-3 logger instance. [optional]
  51          *  - queryLogger: PSR-3 logger instance. [optional]
  52          *  - perfLogger: PSR-3 logger instance. [optional]
  53          *  - errorLogger : Callback that takes an Exception and logs it. [optional]
  54          * @throws InvalidArgumentException
  55          */
  56         public function __construct( array $conf );
  57
  58         /**
  59          * Disables all load balancers. All connections are closed, and any attempt to
  60          * open a new connection will result in a DBAccessError.
  61          * @see ILoadBalancer::disable()
  62          */
  63         public function destroy();
  64
  65         /**
  66          * Create a new load balancer object. The resulting object will be untracked,
  67          * not chronology-protected, and the caller is responsible for cleaning it up.
  68          *
  69          * This method is for only advanced usage and callers should almost always use
  70          * getMainLB() instead. This method can be useful when a table is used as a key/value
  71          * store. In that cases, one might want to query it in autocommit mode (DBO_TRX off)
  72          * but still use DBO_TRX transaction rounds on other tables.
  73          *
  74          * @param bool|string $domain Domain ID, or false for the current domain
  75          * @return ILoadBalancer
  76          */
  77         public function newMainLB( $domain = false );
  78
  79         /**
  80          * Get a cached (tracked) load balancer object.
  81          *
  82          * @param bool|string $domain Domain ID, or false for the current domain
  83          * @return ILoadBalancer
  84          */
  85         public function getMainLB( $domain = false );
  86
  87         /**
  88          * Create a new load balancer for external storage. The resulting object will be
  89          * untracked, not chronology-protected, and the caller is responsible for cleaning it up.
  90          *
  91          * This method is for only advanced usage and callers should almost always use
  92          * getExternalLB() instead. This method can be useful when a table is used as a
  93          * key/value store. In that cases, one might want to query it in autocommit mode
  94          * (DBO_TRX off) but still use DBO_TRX transaction rounds on other tables.
  95          *
  96          * @param string $cluster External storage cluster name
  97          * @return ILoadBalancer
  98          */
  99         public function newExternalLB( $cluster );
 100
 101         /**
 102          * Get a cached (tracked) load balancer for external storage
 103          *
 104          * @param string $cluster External storage cluster name
 105          * @return ILoadBalancer
 106          */
 107         public function getExternalLB( $cluster );
 108
 109         /**
 110          * Get cached (tracked) load balancers for all main database clusters
 111          *
 112          * @return LoadBalancer[] Map of (cluster name => LoadBalancer)
 113          * @since 1.29
 114          */
 115         public function getAllMainLBs();
 116
 117         /**
 118          * Get cached (tracked) load balancers for all external database clusters
 119          *
 120          * @return LoadBalancer[] Map of (cluster name => LoadBalancer)
 121          * @since 1.29
 122          */
 123         public function getAllExternalLBs();
 124
 125         /**
 126          * Execute a function for each tracked load balancer
 127          * The callback is called with the load balancer as the first parameter,
 128          * and $params passed as the subsequent parameters.
 129          *
 130          * @param callable $callback
 131          * @param array $params
 132          */
 133         public function forEachLB( $callback, array $params = [] );
 134
 135         /**
 136          * Prepare all tracked load balancers for shutdown
 137          * @param integer $mode One of the class SHUTDOWN_* constants
 138          * @param callable|null $workCallback Work to mask ChronologyProtector writes
 139          */
 140         public function shutdown(
 141                 $mode = self::SHUTDOWN_CHRONPROT_SYNC, callable $workCallback = null
 142         );
 143
 144         /**
 145          * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot
 146          *
 147          * @param string $fname Caller name
 148          */
 149         public function flushReplicaSnapshots( $fname = __METHOD__ );
 150
 151         /**
 152          * Commit open transactions on all connections. This is useful for two main cases:
 153          *   - a) To commit changes to the masters.
 154          *   - b) To release the snapshot on all connections, master and replica DBs.
 155          * @param string $fname Caller name
 156          * @param array $options Options map:
 157          *   - maxWriteDuration: abort if more than this much time was spent in write queries
 158          */
 159         public function commitAll( $fname = __METHOD__, array $options = [] );
 160
 161         /**
 162          * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set)
 163          *
 164          * The DBO_TRX setting will be reverted to the default in each of these methods:
 165          *   - commitMasterChanges()
 166          *   - rollbackMasterChanges()
 167          *   - commitAll()
 168          *
 169          * This allows for custom transaction rounds from any outer transaction scope.
 170          *
 171          * @param string $fname
 172          * @throws DBTransactionError
 173          */
 174         public function beginMasterChanges( $fname = __METHOD__ );
 175
 176         /**
 177          * Commit changes on all master connections
 178          * @param string $fname Caller name
 179          * @param array $options Options map:
 180          *   - maxWriteDuration: abort if more than this much time was spent in write queries
 181          * @throws Exception
 182          */
 183         public function commitMasterChanges( $fname = __METHOD__, array $options = [] );
 184
 185         /**
 186          * Rollback changes on all master connections
 187          * @param string $fname Caller name
 188          */
 189         public function rollbackMasterChanges( $fname = __METHOD__ );
 190
 191         /**
 192          * Determine if any master connection has pending changes
 193          * @return bool
 194          */
 195         public function hasMasterChanges();
 196
 197         /**
 198          * Detemine if any lagged replica DB connection was used
 199          * @return bool
 200          */
 201         public function laggedReplicaUsed();
 202
 203         /**
 204          * Determine if any master connection has pending/written changes from this request
 205          * @param float $age How many seconds ago is "recent" [defaults to LB lag wait timeout]
 206          * @return bool
 207          */
 208         public function hasOrMadeRecentMasterChanges( $age = null );
 209
 210         /**
 211          * Waits for the replica DBs to catch up to the current master position
 212          *
 213          * Use this when updating very large numbers of rows, as in maintenance scripts,
 214          * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs.
 215          *
 216          * By default this waits on all DB clusters actually used in this request.
 217          * This makes sense when lag being waiting on is caused by the code that does this check.
 218          * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
 219          * that were not changed since the last wait check. To forcefully wait on a specific cluster
 220          * for a given domain, use the 'domain' parameter. To forcefully wait on an "external" cluster,
 221          * use the "cluster" parameter.
 222          *
 223          * Never call this function after a large DB write that is *still* in a transaction.
 224          * It only makes sense to call this after the possible lag inducing changes were committed.
 225          *
 226          * @param array $opts Optional fields that include:
 227          *   - domain : wait on the load balancer DBs that handles the given domain ID
 228          *   - cluster : wait on the given external load balancer DBs
 229          *   - timeout : Max wait time. Default: ~60 seconds
 230          *   - ifWritesSince: Only wait if writes were done since this UNIX timestamp
 231          * @throws DBReplicationWaitError If a timeout or error occured waiting on a DB cluster
 232          */
 233         public function waitForReplication( array $opts = [] );
 234
 235         /**
 236          * Add a callback to be run in every call to waitForReplication() before waiting
 237          *
 238          * Callbacks must clear any transactions that they start
 239          *
 240          * @param string $name Callback name
 241          * @param callable|null $callback Use null to unset a callback
 242          */
 243         public function setWaitForReplicationListener( $name, callable $callback = null );
 244
 245         /**
 246          * Get a token asserting that no transaction writes are active
 247          *
 248          * @param string $fname Caller name (e.g. __METHOD__)
 249          * @return mixed A value to pass to commitAndWaitForReplication()
 250          */
 251         public function getEmptyTransactionTicket( $fname );
 252
 253         /**
 254          * Convenience method for safely running commitMasterChanges()/waitForReplication()
 255          *
 256          * This will commit and wait unless $ticket indicates it is unsafe to do so
 257          *
 258          * @param string $fname Caller name (e.g. __METHOD__)
 259          * @param mixed $ticket Result of getEmptyTransactionTicket()
 260          * @param array $opts Options to waitForReplication()
 261          * @throws DBReplicationWaitError
 262          */
 263         public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] );
 264
 265         /**
 266          * @param string $dbName DB master name (e.g. "db1052")
 267          * @return float|bool UNIX timestamp when client last touched the DB or false if not recent
 268          */
 269         public function getChronologyProtectorTouched( $dbName );
 270
 271         /**
 272          * Disable the ChronologyProtector for all load balancers
 273          *
 274          * This can be called at the start of special API entry points
 275          */
 276         public function disableChronologyProtection();
 277
 278         /**
 279          * Set a new table prefix for the existing local domain ID for testing
 280          *
 281          * @param string $prefix
 282          */
 283         public function setDomainPrefix( $prefix );
 284
 285         /**
 286          * Close all open database connections on all open load balancers.
 287          */
 288         public function closeAll();
 289
 290         /**
 291          * @param string $agent Agent name for query profiling
 292          */
 293         public function setAgentName( $agent );
 294
 295         /**
 296          * Append ?cpPosTime parameter to a URL for ChronologyProtector purposes if needed
 297          *
 298          * Note that unlike cookies, this works accross domains
 299          *
 300          * @param string $url
 301          * @param float $time UNIX timestamp just before shutdown() was called
 302          * @return string
 303          */
 304         public function appendPreShutdownTimeAsQuery( $url, $time );
 305
 306         /**
 307          * @param array $info Map of fields, including:
 308          *   - IPAddress : IP address
 309          *   - UserAgent : User-Agent HTTP header
 310          *   - ChronologyProtection : cookie/header value specifying ChronologyProtector usage
 311          */
 312         public function setRequestInfo( array $info );
 313 }