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 use LoadBalancer;
  28 use DBTransactionError;
  29 use DBReplicationWaitError;
  30
  31 /**
  32  * An interface for generating database load balancers
  33  * @ingroup Database
  34  * @since 1.28
  35  */
  36 interface ILBFactory {
  37         const SHUTDOWN_NO_CHRONPROT = 0; // don't save DB positions at all
  38         const SHUTDOWN_CHRONPROT_ASYNC = 1; // save DB positions, but don't wait on remote DCs
  39         const SHUTDOWN_CHRONPROT_SYNC = 2; // save DB positions, waiting on all DCs
  40
  41         /**
  42          * Construct a manager of ILoadBalancer objects
  43          *
  44          * Sub-classes will extend the required keys in $conf with additional parameters
  45          *
  46          * @param $conf $params Array with keys:
  47          *  - localDomain: A DatabaseDomain or domain ID string.
  48          *  - readOnlyReason : Reason the master DB is read-only if so [optional]
  49          *  - srvCache : BagOStuff object for server cache [optional]
  50          *  - memCache : BagOStuff object for cluster memory cache [optional]
  51          *  - wanCache : WANObjectCache object [optional]
  52          *  - hostname : The name of the current server [optional]
  53          *  - cliMode: Whether the execution context is a CLI script. [optional]
  54          *  - profiler : Class name or instance with profileIn()/profileOut() methods. [optional]
  55          *  - trxProfiler: TransactionProfiler instance. [optional]
  56          *  - replLogger: PSR-3 logger instance. [optional]
  57          *  - connLogger: PSR-3 logger instance. [optional]
  58          *  - queryLogger: PSR-3 logger instance. [optional]
  59          *  - perfLogger: PSR-3 logger instance. [optional]
  60          *  - errorLogger : Callback that takes an Exception and logs it. [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          * Create a new load balancer object. The resulting object will be untracked,
  74          * not chronology-protected, and the caller is responsible for cleaning it up.
  75          *
  76          * This method is for only advanced usage and callers should almost always use
  77          * getMainLB() instead. This method can be useful when a table is used as a key/value
  78          * store. In that cases, one might want to query it in autocommit mode (DBO_TRX off)
  79          * but still use DBO_TRX transaction rounds on other tables.
  80          *
  81          * @param bool|string $domain Domain ID, or false for the current domain
  82          * @return ILoadBalancer
  83          */
  84         public function newMainLB( $domain = false );
  85
  86         /**
  87          * Get a cached (tracked) load balancer object.
  88          *
  89          * @param bool|string $domain Domain ID, or false for the current domain
  90          * @return ILoadBalancer
  91          */
  92         public function getMainLB( $domain = false );
  93
  94         /**
  95          * Create a new load balancer for external storage. The resulting object will be
  96          * untracked, not chronology-protected, and the caller is responsible for cleaning it up.
  97          *
  98          * This method is for only advanced usage and callers should almost always use
  99          * getExternalLB() instead. This method can be useful when a table is used as a
 100          * key/value store. In that cases, one might want to query it in autocommit mode
 101          * (DBO_TRX off) but still use DBO_TRX transaction rounds on other tables.
 102          *
 103          * @param string $cluster External storage cluster name
 104          * @return ILoadBalancer
 105          */
 106         public function newExternalLB( $cluster );
 107
 108         /**
 109          * Get a cached (tracked) load balancer for external storage
 110          *
 111          * @param string $cluster External storage cluster name
 112          * @return ILoadBalancer
 113          */
 114         public function getExternalLB( $cluster );
 115
 116         /**
 117          * Get cached (tracked) load balancers for all main database clusters
 118          *
 119          * @return LoadBalancer[] Map of (cluster name => LoadBalancer)
 120          * @since 1.29
 121          */
 122         public function getAllMainLBs();
 123
 124         /**
 125          * Get cached (tracked) load balancers for all external database clusters
 126          *
 127          * @return LoadBalancer[] Map of (cluster name => LoadBalancer)
 128          * @since 1.29
 129          */
 130         public function getAllExternalLBs();
 131
 132         /**
 133          * Execute a function for each tracked load balancer
 134          * The callback is called with the load balancer as the first parameter,
 135          * and $params passed as the subsequent parameters.
 136          *
 137          * @param callable $callback
 138          * @param array $params
 139          */
 140         public function forEachLB( $callback, array $params = [] );
 141
 142         /**
 143          * Prepare all tracked load balancers for shutdown
 144          * @param integer $mode One of the class SHUTDOWN_* constants
 145          * @param callable|null $workCallback Work to mask ChronologyProtector writes
 146          */
 147         public function shutdown(
 148                 $mode = self::SHUTDOWN_CHRONPROT_SYNC, callable $workCallback = null
 149         );
 150
 151         /**
 152          * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot
 153          *
 154          * @param string $fname Caller name
 155          */
 156         public function flushReplicaSnapshots( $fname = __METHOD__ );
 157
 158         /**
 159          * Commit open transactions on all connections. This is useful for two main cases:
 160          *   - a) To commit changes to the masters.
 161          *   - b) To release the snapshot on all connections, master and replica DBs.
 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          */
 166         public function commitAll( $fname = __METHOD__, array $options = [] );
 167
 168         /**
 169          * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set)
 170          *
 171          * The DBO_TRX setting will be reverted to the default in each of these methods:
 172          *   - commitMasterChanges()
 173          *   - rollbackMasterChanges()
 174          *   - commitAll()
 175          *
 176          * This allows for custom transaction rounds from any outer transaction scope.
 177          *
 178          * @param string $fname
 179          * @throws DBTransactionError
 180          */
 181         public function beginMasterChanges( $fname = __METHOD__ );
 182
 183         /**
 184          * Commit changes on all master connections
 185          * @param string $fname Caller name
 186          * @param array $options Options map:
 187          *   - maxWriteDuration: abort if more than this much time was spent in write queries
 188          * @throws DBTransactionError
 189          */
 190         public function commitMasterChanges( $fname = __METHOD__, array $options = [] );
 191
 192         /**
 193          * Rollback changes on all master connections
 194          * @param string $fname Caller name
 195          */
 196         public function rollbackMasterChanges( $fname = __METHOD__ );
 197
 198         /**
 199          * Determine if any master connection has pending changes
 200          * @return bool
 201          */
 202         public function hasMasterChanges();
 203
 204         /**
 205          * Detemine if any lagged replica DB connection was used
 206          * @return bool
 207          */
 208         public function laggedReplicaUsed();
 209
 210         /**
 211          * Determine if any master connection has pending/written changes from this request
 212          * @param float $age How many seconds ago is "recent" [defaults to LB lag wait timeout]
 213          * @return bool
 214          */
 215         public function hasOrMadeRecentMasterChanges( $age = null );
 216
 217         /**
 218          * Waits for the replica DBs to catch up to the current master position
 219          *
 220          * Use this when updating very large numbers of rows, as in maintenance scripts,
 221          * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs.
 222          *
 223          * By default this waits on all DB clusters actually used in this request.
 224          * This makes sense when lag being waiting on is caused by the code that does this check.
 225          * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
 226          * that were not changed since the last wait check. To forcefully wait on a specific cluster
 227          * for a given domain, use the 'domain' parameter. To forcefully wait on an "external" cluster,
 228          * use the "cluster" parameter.
 229          *
 230          * Never call this function after a large DB write that is *still* in a transaction.
 231          * It only makes sense to call this after the possible lag inducing changes were committed.
 232          *
 233          * @param array $opts Optional fields that include:
 234          *   - domain : wait on the load balancer DBs that handles the given domain ID
 235          *   - cluster : wait on the given external load balancer DBs
 236          *   - timeout : Max wait time. Default: ~60 seconds
 237          *   - ifWritesSince: Only wait if writes were done since this UNIX timestamp
 238          * @throws DBReplicationWaitError If a timeout or error occured waiting on a DB cluster
 239          */
 240         public function waitForReplication( array $opts = [] );
 241
 242         /**
 243          * Add a callback to be run in every call to waitForReplication() before waiting
 244          *
 245          * Callbacks must clear any transactions that they start
 246          *
 247          * @param string $name Callback name
 248          * @param callable|null $callback Use null to unset a callback
 249          */
 250         public function setWaitForReplicationListener( $name, callable $callback = null );
 251
 252         /**
 253          * Get a token asserting that no transaction writes are active
 254          *
 255          * @param string $fname Caller name (e.g. __METHOD__)
 256          * @return mixed A value to pass to commitAndWaitForReplication()
 257          */
 258         public function getEmptyTransactionTicket( $fname );
 259
 260         /**
 261          * Convenience method for safely running commitMasterChanges()/waitForReplication()
 262          *
 263          * This will commit and wait unless $ticket indicates it is unsafe to do so
 264          *
 265          * @param string $fname Caller name (e.g. __METHOD__)
 266          * @param mixed $ticket Result of getEmptyTransactionTicket()
 267          * @param array $opts Options to waitForReplication()
 268          * @throws DBReplicationWaitError
 269          */
 270         public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] );
 271
 272         /**
 273          * @param string $dbName DB master name (e.g. "db1052")
 274          * @return float|bool UNIX timestamp when client last touched the DB or false if not recent
 275          */
 276         public function getChronologyProtectorTouched( $dbName );
 277
 278         /**
 279          * Disable the ChronologyProtector for all load balancers
 280          *
 281          * This can be called at the start of special API entry points
 282          */
 283         public function disableChronologyProtection();
 284
 285         /**
 286          * Set a new table prefix for the existing local domain ID for testing
 287          *
 288          * @param string $prefix
 289          */
 290         public function setDomainPrefix( $prefix );
 291
 292         /**
 293          * Close all open database connections on all open load balancers.
 294          */
 295         public function closeAll();
 296
 297         /**
 298          * @param string $agent Agent name for query profiling
 299          */
 300         public function setAgentName( $agent );
 301
 302         /**
 303          * Append ?cpPosTime parameter to a URL for ChronologyProtector purposes if needed
 304          *
 305          * Note that unlike cookies, this works accross domains
 306          *
 307          * @param string $url
 308          * @param float $time UNIX timestamp just before shutdown() was called
 309          * @return string
 310          */
 311         public function appendPreShutdownTimeAsQuery( $url, $time );
 312
 313         /**
 314          * @param array $info Map of fields, including:
 315          *   - IPAddress : IP address
 316          *   - UserAgent : User-Agent HTTP header
 317          *   - ChronologyProtection : cookie/header value specifying ChronologyProtector usage
 318          */
 319         public function setRequestInfo( array $info );
 320 }