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