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          * Execute a function for each tracked load balancer
 111          * The callback is called with the load balancer as the first parameter,
 112          * and $params passed as the subsequent parameters.
 113          *
 114          * @param callable $callback
 115          * @param array $params
 116          */
 117         public function forEachLB( $callback, array $params = [] );
 118
 119         /**
 120          * Prepare all tracked load balancers for shutdown
 121          * @param integer $mode One of the class SHUTDOWN_* constants
 122          * @param callable|null $workCallback Work to mask ChronologyProtector writes
 123          */
 124         public function shutdown(
 125                 $mode = self::SHUTDOWN_CHRONPROT_SYNC, callable $workCallback = null
 126         );
 127
 128         /**
 129          * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot
 130          *
 131          * @param string $fname Caller name
 132          */
 133         public function flushReplicaSnapshots( $fname = __METHOD__ );
 134
 135         /**
 136          * Commit open transactions on all connections. This is useful for two main cases:
 137          *   - a) To commit changes to the masters.
 138          *   - b) To release the snapshot on all connections, master and replica DBs.
 139          * @param string $fname Caller name
 140          * @param array $options Options map:
 141          *   - maxWriteDuration: abort if more than this much time was spent in write queries
 142          */
 143         public function commitAll( $fname = __METHOD__, array $options = [] );
 144
 145         /**
 146          * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set)
 147          *
 148          * The DBO_TRX setting will be reverted to the default in each of these methods:
 149          *   - commitMasterChanges()
 150          *   - rollbackMasterChanges()
 151          *   - commitAll()
 152          *
 153          * This allows for custom transaction rounds from any outer transaction scope.
 154          *
 155          * @param string $fname
 156          * @throws DBTransactionError
 157          */
 158         public function beginMasterChanges( $fname = __METHOD__ );
 159
 160         /**
 161          * Commit changes on all master connections
 162          * @param string $fname Caller name
 163          * @param array $options Options map:
 164          *   - maxWriteDuration: abort if more than this much time was spent in write queries
 165          * @throws Exception
 166          */
 167         public function commitMasterChanges( $fname = __METHOD__, array $options = [] );
 168
 169         /**
 170          * Rollback changes on all master connections
 171          * @param string $fname Caller name
 172          */
 173         public function rollbackMasterChanges( $fname = __METHOD__ );
 174
 175         /**
 176          * Determine if any master connection has pending changes
 177          * @return bool
 178          */
 179         public function hasMasterChanges();
 180
 181         /**
 182          * Detemine if any lagged replica DB connection was used
 183          * @return bool
 184          */
 185         public function laggedReplicaUsed();
 186
 187         /**
 188          * Determine if any master connection has pending/written changes from this request
 189          * @param float $age How many seconds ago is "recent" [defaults to LB lag wait timeout]
 190          * @return bool
 191          */
 192         public function hasOrMadeRecentMasterChanges( $age = null );
 193
 194         /**
 195          * Waits for the replica DBs to catch up to the current master position
 196          *
 197          * Use this when updating very large numbers of rows, as in maintenance scripts,
 198          * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs.
 199          *
 200          * By default this waits on all DB clusters actually used in this request.
 201          * This makes sense when lag being waiting on is caused by the code that does this check.
 202          * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
 203          * that were not changed since the last wait check. To forcefully wait on a specific cluster
 204          * for a given domain, use the 'domain' parameter. To forcefully wait on an "external" cluster,
 205          * use the "cluster" parameter.
 206          *
 207          * Never call this function after a large DB write that is *still* in a transaction.
 208          * It only makes sense to call this after the possible lag inducing changes were committed.
 209          *
 210          * @param array $opts Optional fields that include:
 211          *   - domain : wait on the load balancer DBs that handles the given domain ID
 212          *   - cluster : wait on the given external load balancer DBs
 213          *   - timeout : Max wait time. Default: ~60 seconds
 214          *   - ifWritesSince: Only wait if writes were done since this UNIX timestamp
 215          * @throws DBReplicationWaitError If a timeout or error occured waiting on a DB cluster
 216          */
 217         public function waitForReplication( array $opts = [] );
 218
 219         /**
 220          * Add a callback to be run in every call to waitForReplication() before waiting
 221          *
 222          * Callbacks must clear any transactions that they start
 223          *
 224          * @param string $name Callback name
 225          * @param callable|null $callback Use null to unset a callback
 226          */
 227         public function setWaitForReplicationListener( $name, callable $callback = null );
 228
 229         /**
 230          * Get a token asserting that no transaction writes are active
 231          *
 232          * @param string $fname Caller name (e.g. __METHOD__)
 233          * @return mixed A value to pass to commitAndWaitForReplication()
 234          */
 235         public function getEmptyTransactionTicket( $fname );
 236
 237         /**
 238          * Convenience method for safely running commitMasterChanges()/waitForReplication()
 239          *
 240          * This will commit and wait unless $ticket indicates it is unsafe to do so
 241          *
 242          * @param string $fname Caller name (e.g. __METHOD__)
 243          * @param mixed $ticket Result of getEmptyTransactionTicket()
 244          * @param array $opts Options to waitForReplication()
 245          * @throws DBReplicationWaitError
 246          */
 247         public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] );
 248
 249         /**
 250          * @param string $dbName DB master name (e.g. "db1052")
 251          * @return float|bool UNIX timestamp when client last touched the DB or false if not recent
 252          */
 253         public function getChronologyProtectorTouched( $dbName );
 254
 255         /**
 256          * Disable the ChronologyProtector for all load balancers
 257          *
 258          * This can be called at the start of special API entry points
 259          */
 260         public function disableChronologyProtection();
 261
 262         /**
 263          * Set a new table prefix for the existing local domain ID for testing
 264          *
 265          * @param string $prefix
 266          */
 267         public function setDomainPrefix( $prefix );
 268
 269         /**
 270          * Close all open database connections on all open load balancers.
 271          */
 272         public function closeAll();
 273
 274         /**
 275          * @param string $agent Agent name for query profiling
 276          */
 277         public function setAgentName( $agent );
 278
 279         /**
 280          * Append ?cpPosTime parameter to a URL for ChronologyProtector purposes if needed
 281          *
 282          * Note that unlike cookies, this works accross domains
 283          *
 284          * @param string $url
 285          * @param float $time UNIX timestamp just before shutdown() was called
 286          * @return string
 287          */
 288         public function appendPreShutdownTimeAsQuery( $url, $time );
 289
 290         /**
 291          * @param array $info Map of fields, including:
 292          *   - IPAddress : IP address
 293          *   - UserAgent : User-Agent HTTP header
 294          *   - ChronologyProtection : cookie/header value specifying ChronologyProtector usage
 295          */
 296         public function setRequestInfo( array $info );
 297 }