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 ILoadBalancer;
  28 use LoadBalancer;
  29 use DBTransactionError;
  30 use DBReplicationWaitError;
  31
  32 /**
  33  * An interface for generating database load balancers
  34  * @ingroup Database
  35  * @since 1.28
  36  */
  37 interface ILBFactory {
  38         const SHUTDOWN_NO_CHRONPROT = 0; // don't save DB positions at all
  39         const SHUTDOWN_CHRONPROT_ASYNC = 1; // save DB positions, but don't wait on remote DCs
  40         const SHUTDOWN_CHRONPROT_SYNC = 2; // save DB positions, waiting on all DCs
  41
  42         /**
  43          * Construct a manager of ILoadBalancer objects
  44          *
  45          * Sub-classes will extend the required keys in $conf with additional parameters
  46          *
  47          * @param $conf $params Array with keys:
  48          *  - localDomain: A DatabaseDomain or domain ID string.
  49          *  - readOnlyReason : Reason the master DB is read-only if so [optional]
  50          *  - srvCache : BagOStuff object for server cache [optional]
  51          *  - memCache : BagOStuff object for cluster memory cache [optional]
  52          *  - wanCache : WANObjectCache object [optional]
  53          *  - hostname : The name of the current server [optional]
  54          *  - cliMode: Whether the execution context is a CLI script. [optional]
  55          *  - profiler : Class name or instance with profileIn()/profileOut() methods. [optional]
  56          *  - trxProfiler: TransactionProfiler instance. [optional]
  57          *  - replLogger: PSR-3 logger instance. [optional]
  58          *  - connLogger: PSR-3 logger instance. [optional]
  59          *  - queryLogger: PSR-3 logger instance. [optional]
  60          *  - perfLogger: PSR-3 logger instance. [optional]
  61          *  - errorLogger : Callback that takes an Exception and logs it. [optional]
  62          * @throws InvalidArgumentException
  63          */
  64         public function __construct( array $conf );
  65
  66         /**
  67          * Disables all load balancers. All connections are closed, and any attempt to
  68          * open a new connection will result in a DBAccessError.
  69          * @see ILoadBalancer::disable()
  70          */
  71         public function destroy();
  72
  73         /**
  74          * Create a new load balancer object. The resulting object will be untracked,
  75          * not chronology-protected, and the caller is responsible for cleaning it up.
  76          *
  77          * This method is for only advanced usage and callers should almost always use
  78          * getMainLB() instead. This method can be useful when a table is used as a key/value
  79          * store. In that cases, one might want to query it in autocommit mode (DBO_TRX off)
  80          * but still use DBO_TRX transaction rounds on other tables.
  81          *
  82          * @param bool|string $domain Domain ID, or false for the current domain
  83          * @return ILoadBalancer
  84          */
  85         public function newMainLB( $domain = false );
  86
  87         /**
  88          * Get a cached (tracked) load balancer object.
  89          *
  90          * @param bool|string $domain Domain ID, or false for the current domain
  91          * @return ILoadBalancer
  92          */
  93         public function getMainLB( $domain = false );
  94
  95         /**
  96          * Create a new load balancer for external storage. The resulting object will be
  97          * untracked, not chronology-protected, and the caller is responsible for cleaning it up.
  98          *
  99          * This method is for only advanced usage and callers should almost always use
 100          * getExternalLB() instead. This method can be useful when a table is used as a
 101          * key/value store. In that cases, one might want to query it in autocommit mode
 102          * (DBO_TRX off) but still use DBO_TRX transaction rounds on other tables.
 103          *
 104          * @param string $cluster External storage cluster name
 105          * @return ILoadBalancer
 106          */
 107         public function newExternalLB( $cluster );
 108
 109         /**
 110          * Get a cached (tracked) load balancer for external storage
 111          *
 112          * @param string $cluster External storage cluster name
 113          * @return ILoadBalancer
 114          */
 115         public function getExternalLB( $cluster );
 116
 117         /**
 118          * Get cached (tracked) load balancers for all main database clusters
 119          *
 120          * @return LoadBalancer[] Map of (cluster name => LoadBalancer)
 121          * @since 1.29
 122          */
 123         public function getAllMainLBs();
 124
 125         /**
 126          * Get cached (tracked) load balancers for all external database clusters
 127          *
 128          * @return LoadBalancer[] Map of (cluster name => LoadBalancer)
 129          * @since 1.29
 130          */
 131         public function getAllExternalLBs();
 132
 133         /**
 134          * Execute a function for each tracked load balancer
 135          * The callback is called with the load balancer as the first parameter,
 136          * and $params passed as the subsequent parameters.
 137          *
 138          * @param callable $callback
 139          * @param array $params
 140          */
 141         public function forEachLB( $callback, array $params = [] );
 142
 143         /**
 144          * Prepare all tracked load balancers for shutdown
 145          * @param integer $mode One of the class SHUTDOWN_* constants
 146          * @param callable|null $workCallback Work to mask ChronologyProtector writes
 147          */
 148         public function shutdown(
 149                 $mode = self::SHUTDOWN_CHRONPROT_SYNC, callable $workCallback = null
 150         );
 151
 152         /**
 153          * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot
 154          *
 155          * @param string $fname Caller name
 156          */
 157         public function flushReplicaSnapshots( $fname = __METHOD__ );
 158
 159         /**
 160          * Commit open transactions on all connections. This is useful for two main cases:
 161          *   - a) To commit changes to the masters.
 162          *   - b) To release the snapshot on all connections, master and replica DBs.
 163          * @param string $fname Caller name
 164          * @param array $options Options map:
 165          *   - maxWriteDuration: abort if more than this much time was spent in write queries
 166          */
 167         public function commitAll( $fname = __METHOD__, array $options = [] );
 168
 169         /**
 170          * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set)
 171          *
 172          * The DBO_TRX setting will be reverted to the default in each of these methods:
 173          *   - commitMasterChanges()
 174          *   - rollbackMasterChanges()
 175          *   - commitAll()
 176          *
 177          * This allows for custom transaction rounds from any outer transaction scope.
 178          *
 179          * @param string $fname
 180          * @throws DBTransactionError
 181          */
 182         public function beginMasterChanges( $fname = __METHOD__ );
 183
 184         /**
 185          * Commit changes on all master connections
 186          * @param string $fname Caller name
 187          * @param array $options Options map:
 188          *   - maxWriteDuration: abort if more than this much time was spent in write queries
 189          * @throws DBTransactionError
 190          */
 191         public function commitMasterChanges( $fname = __METHOD__, array $options = [] );
 192
 193         /**
 194          * Rollback changes on all master connections
 195          * @param string $fname Caller name
 196          */
 197         public function rollbackMasterChanges( $fname = __METHOD__ );
 198
 199         /**
 200          * Determine if any master connection has pending changes
 201          * @return bool
 202          */
 203         public function hasMasterChanges();
 204
 205         /**
 206          * Detemine if any lagged replica DB connection was used
 207          * @return bool
 208          */
 209         public function laggedReplicaUsed();
 210
 211         /**
 212          * Determine if any master connection has pending/written changes from this request
 213          * @param float $age How many seconds ago is "recent" [defaults to LB lag wait timeout]
 214          * @return bool
 215          */
 216         public function hasOrMadeRecentMasterChanges( $age = null );
 217
 218         /**
 219          * Waits for the replica DBs to catch up to the current master position
 220          *
 221          * Use this when updating very large numbers of rows, as in maintenance scripts,
 222          * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs.
 223          *
 224          * By default this waits on all DB clusters actually used in this request.
 225          * This makes sense when lag being waiting on is caused by the code that does this check.
 226          * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
 227          * that were not changed since the last wait check. To forcefully wait on a specific cluster
 228          * for a given domain, use the 'domain' parameter. To forcefully wait on an "external" cluster,
 229          * use the "cluster" parameter.
 230          *
 231          * Never call this function after a large DB write that is *still* in a transaction.
 232          * It only makes sense to call this after the possible lag inducing changes were committed.
 233          *
 234          * @param array $opts Optional fields that include:
 235          *   - domain : wait on the load balancer DBs that handles the given domain ID
 236          *   - cluster : wait on the given external load balancer DBs
 237          *   - timeout : Max wait time. Default: ~60 seconds
 238          *   - ifWritesSince: Only wait if writes were done since this UNIX timestamp
 239          * @throws DBReplicationWaitError If a timeout or error occured waiting on a DB cluster
 240          */
 241         public function waitForReplication( array $opts = [] );
 242
 243         /**
 244          * Add a callback to be run in every call to waitForReplication() before waiting
 245          *
 246          * Callbacks must clear any transactions that they start
 247          *
 248          * @param string $name Callback name
 249          * @param callable|null $callback Use null to unset a callback
 250          */
 251         public function setWaitForReplicationListener( $name, callable $callback = null );
 252
 253         /**
 254          * Get a token asserting that no transaction writes are active
 255          *
 256          * @param string $fname Caller name (e.g. __METHOD__)
 257          * @return mixed A value to pass to commitAndWaitForReplication()
 258          */
 259         public function getEmptyTransactionTicket( $fname );
 260
 261         /**
 262          * Convenience method for safely running commitMasterChanges()/waitForReplication()
 263          *
 264          * This will commit and wait unless $ticket indicates it is unsafe to do so
 265          *
 266          * @param string $fname Caller name (e.g. __METHOD__)
 267          * @param mixed $ticket Result of getEmptyTransactionTicket()
 268          * @param array $opts Options to waitForReplication()
 269          * @throws DBReplicationWaitError
 270          */
 271         public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] );
 272
 273         /**
 274          * @param string $dbName DB master name (e.g. "db1052")
 275          * @return float|bool UNIX timestamp when client last touched the DB or false if not recent
 276          */
 277         public function getChronologyProtectorTouched( $dbName );
 278
 279         /**
 280          * Disable the ChronologyProtector for all load balancers
 281          *
 282          * This can be called at the start of special API entry points
 283          */
 284         public function disableChronologyProtection();
 285
 286         /**
 287          * Set a new table prefix for the existing local domain ID for testing
 288          *
 289          * @param string $prefix
 290          */
 291         public function setDomainPrefix( $prefix );
 292
 293         /**
 294          * Close all open database connections on all open load balancers.
 295          */
 296         public function closeAll();
 297
 298         /**
 299          * @param string $agent Agent name for query profiling
 300          */
 301         public function setAgentName( $agent );
 302
 303         /**
 304          * Append ?cpPosTime parameter to a URL for ChronologyProtector purposes if needed
 305          *
 306          * Note that unlike cookies, this works accross domains
 307          *
 308          * @param string $url
 309          * @param float $time UNIX timestamp just before shutdown() was called
 310          * @return string
 311          */
 312         public function appendPreShutdownTimeAsQuery( $url, $time );
 313
 314         /**
 315          * @param array $info Map of fields, including:
 316          *   - IPAddress : IP address
 317          *   - UserAgent : User-Agent HTTP header
 318          *   - ChronologyProtection : cookie/header value specifying ChronologyProtector usage
 319          */
 320         public function setRequestInfo( array $info );
 321 }