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
  28 /**
  29  * An interface for generating database load balancers
  30  * @ingroup Database
  31  * @since 1.28
  32  */
  33 interface ILBFactory {
  34         const SHUTDOWN_NO_CHRONPROT = 0; // don't save DB positions at all
  35         const SHUTDOWN_CHRONPROT_ASYNC = 1; // save DB positions, but don't wait on remote DCs
  36         const SHUTDOWN_CHRONPROT_SYNC = 2; // save DB positions, waiting on all DCs
  37
  38         /**
  39          * Construct a manager of ILoadBalancer objects
  40          *
  41          * Sub-classes will extend the required keys in $conf with additional parameters
  42          *
  43          * @param array $conf Array with keys:
  44          *  - localDomain: A DatabaseDomain or domain ID string.
  45          *  - readOnlyReason : Reason the master DB is read-only if so [optional]
  46          *  - srvCache : BagOStuff object for server cache [optional]
  47          *  - memStash : BagOStuff object for cross-datacenter memory storage [optional]
  48          *  - wanCache : WANObjectCache object [optional]
  49          *  - hostname : The name of the current server [optional]
  50          *  - cliMode: Whether the execution context is a CLI script. [optional]
  51          *  - profiler : Class name or instance with profileIn()/profileOut() methods. [optional]
  52          *  - trxProfiler: TransactionProfiler instance. [optional]
  53          *  - replLogger: PSR-3 logger instance. [optional]
  54          *  - connLogger: PSR-3 logger instance. [optional]
  55          *  - queryLogger: PSR-3 logger instance. [optional]
  56          *  - perfLogger: PSR-3 logger instance. [optional]
  57          *  - errorLogger : Callback that takes an Exception and logs it. [optional]
  58          * @throws InvalidArgumentException
  59          */
  60         public function __construct( array $conf );
  61
  62         /**
  63          * Disables all load balancers. All connections are closed, and any attempt to
  64          * open a new connection will result in a DBAccessError.
  65          * @see ILoadBalancer::disable()
  66          */
  67         public function destroy();
  68
  69         /**
  70          * Create a new load balancer object. The resulting object will be untracked,
  71          * not chronology-protected, and the caller is responsible for cleaning it up.
  72          *
  73          * This method is for only advanced usage and callers should almost always use
  74          * getMainLB() instead. This method can be useful when a table is used as a key/value
  75          * store. In that cases, one might want to query it in autocommit mode (DBO_TRX off)
  76          * but still use DBO_TRX transaction rounds on other tables.
  77          *
  78          * @param bool|string $domain Domain ID, or false for the current domain
  79          * @return ILoadBalancer
  80          */
  81         public function newMainLB( $domain = false );
  82
  83         /**
  84          * Get a cached (tracked) load balancer object.
  85          *
  86          * @param bool|string $domain Domain ID, or false for the current domain
  87          * @return ILoadBalancer
  88          */
  89         public function getMainLB( $domain = false );
  90
  91         /**
  92          * Create a new load balancer for external storage. The resulting object will be
  93          * untracked, not chronology-protected, and the caller is responsible for cleaning it up.
  94          *
  95          * This method is for only advanced usage and callers should almost always use
  96          * getExternalLB() instead. This method can be useful when a table is used as a
  97          * key/value store. In that cases, one might want to query it in autocommit mode
  98          * (DBO_TRX off) but still use DBO_TRX transaction rounds on other tables.
  99          *
 100          * @param string $cluster External storage cluster name
 101          * @return ILoadBalancer
 102          */
 103         public function newExternalLB( $cluster );
 104
 105         /**
 106          * Get a cached (tracked) load balancer for external storage
 107          *
 108          * @param string $cluster External storage cluster name
 109          * @return ILoadBalancer
 110          */
 111         public function getExternalLB( $cluster );
 112
 113         /**
 114          * Get cached (tracked) load balancers for all main database clusters
 115          *
 116          * @return LoadBalancer[] Map of (cluster name => LoadBalancer)
 117          * @since 1.29
 118          */
 119         public function getAllMainLBs();
 120
 121         /**
 122          * Get cached (tracked) load balancers for all external database clusters
 123          *
 124          * @return LoadBalancer[] Map of (cluster name => LoadBalancer)
 125          * @since 1.29
 126          */
 127         public function getAllExternalLBs();
 128
 129         /**
 130          * Execute a function for each tracked load balancer
 131          * The callback is called with the load balancer as the first parameter,
 132          * and $params passed as the subsequent parameters.
 133          *
 134          * @param callable $callback
 135          * @param array $params
 136          */
 137         public function forEachLB( $callback, array $params = [] );
 138
 139         /**
 140          * Prepare all tracked load balancers for shutdown
 141          * @param int $mode One of the class SHUTDOWN_* constants
 142          * @param callable|null $workCallback Work to mask ChronologyProtector writes
 143          * @param int|null &$cpIndex Position key write counter for ChronologyProtector
 144          */
 145         public function shutdown(
 146                 $mode = self::SHUTDOWN_CHRONPROT_SYNC, callable $workCallback = null, &$cpIndex = null
 147         );
 148
 149         /**
 150          * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot
 151          *
 152          * @param string $fname Caller name
 153          */
 154         public function flushReplicaSnapshots( $fname = __METHOD__ );
 155
 156         /**
 157          * Commit open transactions on all connections. This is useful for two main cases:
 158          *   - a) To commit changes to the masters.
 159          *   - b) To release the snapshot on all connections, master and replica DBs.
 160          * @param string $fname Caller name
 161          * @param array $options Options map:
 162          *   - maxWriteDuration: abort if more than this much time was spent in write queries
 163          */
 164         public function commitAll( $fname = __METHOD__, array $options = [] );
 165
 166         /**
 167          * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set)
 168          *
 169          * The DBO_TRX setting will be reverted to the default in each of these methods:
 170          *   - commitMasterChanges()
 171          *   - rollbackMasterChanges()
 172          *   - commitAll()
 173          *
 174          * This allows for custom transaction rounds from any outer transaction scope.
 175          *
 176          * @param string $fname
 177          * @throws DBTransactionError
 178          */
 179         public function beginMasterChanges( $fname = __METHOD__ );
 180
 181         /**
 182          * Commit changes on all master connections
 183          * @param string $fname Caller name
 184          * @param array $options Options map:
 185          *   - maxWriteDuration: abort if more than this much time was spent in write queries
 186          * @throws DBTransactionError
 187          */
 188         public function commitMasterChanges( $fname = __METHOD__, array $options = [] );
 189
 190         /**
 191          * Rollback changes on all master connections
 192          * @param string $fname Caller name
 193          */
 194         public function rollbackMasterChanges( $fname = __METHOD__ );
 195
 196         /**
 197          * Check if a transaction round is active
 198          * @return bool
 199          * @since 1.29
 200          */
 201         public function hasTransactionRound();
 202
 203         /**
 204          * Determine if any master connection has pending changes
 205          * @return bool
 206          */
 207         public function hasMasterChanges();
 208
 209         /**
 210          * Detemine if any lagged replica DB connection was used
 211          * @return bool
 212          */
 213         public function laggedReplicaUsed();
 214
 215         /**
 216          * Determine if any master connection has pending/written changes from this request
 217          * @param float $age How many seconds ago is "recent" [defaults to LB lag wait timeout]
 218          * @return bool
 219          */
 220         public function hasOrMadeRecentMasterChanges( $age = null );
 221
 222         /**
 223          * Waits for the replica DBs to catch up to the current master position
 224          *
 225          * Use this when updating very large numbers of rows, as in maintenance scripts,
 226          * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs.
 227          *
 228          * By default this waits on all DB clusters actually used in this request.
 229          * This makes sense when lag being waiting on is caused by the code that does this check.
 230          * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
 231          * that were not changed since the last wait check. To forcefully wait on a specific cluster
 232          * for a given domain, use the 'domain' parameter. To forcefully wait on an "external" cluster,
 233          * use the "cluster" parameter.
 234          *
 235          * Never call this function after a large DB write that is *still* in a transaction.
 236          * It only makes sense to call this after the possible lag inducing changes were committed.
 237          *
 238          * @param array $opts Optional fields that include:
 239          *   - domain : wait on the load balancer DBs that handles the given domain ID
 240          *   - cluster : wait on the given external load balancer DBs
 241          *   - timeout : Max wait time. Default: ~60 seconds
 242          *   - ifWritesSince: Only wait if writes were done since this UNIX timestamp
 243          * @throws DBReplicationWaitError If a timeout or error occurred waiting on a DB cluster
 244          */
 245         public function waitForReplication( array $opts = [] );
 246
 247         /**
 248          * Add a callback to be run in every call to waitForReplication() before waiting
 249          *
 250          * Callbacks must clear any transactions that they start
 251          *
 252          * @param string $name Callback name
 253          * @param callable|null $callback Use null to unset a callback
 254          */
 255         public function setWaitForReplicationListener( $name, callable $callback = null );
 256
 257         /**
 258          * Get a token asserting that no transaction writes are active
 259          *
 260          * @param string $fname Caller name (e.g. __METHOD__)
 261          * @return mixed A value to pass to commitAndWaitForReplication()
 262          */
 263         public function getEmptyTransactionTicket( $fname );
 264
 265         /**
 266          * Convenience method for safely running commitMasterChanges()/waitForReplication()
 267          *
 268          * This will commit and wait unless $ticket indicates it is unsafe to do so
 269          *
 270          * @param string $fname Caller name (e.g. __METHOD__)
 271          * @param mixed $ticket Result of getEmptyTransactionTicket()
 272          * @param array $opts Options to waitForReplication()
 273          * @throws DBReplicationWaitError
 274          */
 275         public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] );
 276
 277         /**
 278          * @param string $dbName DB master name (e.g. "db1052")
 279          * @return float|bool UNIX timestamp when client last touched the DB or false if not recent
 280          */
 281         public function getChronologyProtectorTouched( $dbName );
 282
 283         /**
 284          * Disable the ChronologyProtector for all load balancers
 285          *
 286          * This can be called at the start of special API entry points
 287          */
 288         public function disableChronologyProtection();
 289
 290         /**
 291          * Set a new table prefix for the existing local domain ID for testing
 292          *
 293          * @param string $prefix
 294          */
 295         public function setDomainPrefix( $prefix );
 296
 297         /**
 298          * Close all open database connections on all open load balancers.
 299          */
 300         public function closeAll();
 301
 302         /**
 303          * @param string $agent Agent name for query profiling
 304          */
 305         public function setAgentName( $agent );
 306
 307         /**
 308          * Append ?cpPosIndex parameter to a URL for ChronologyProtector purposes if needed
 309          *
 310          * Note that unlike cookies, this works accross domains
 311          *
 312          * @param string $url
 313          * @param float $time UNIX timestamp just before shutdown() was called
 314          * @return string
 315          */
 316         public function appendShutdownCPIndexAsQuery( $url, $time );
 317
 318         /**
 319          * @param array $info Map of fields, including:
 320          *   - IPAddress : IP address
 321          *   - UserAgent : User-Agent HTTP header
 322          *   - ChronologyProtection : cookie/header value specifying ChronologyProtector usage
 323          *   - ChronologyPositionIndex: timestamp used to get up-to-date DB positions for the agent
 324          */
 325         public function setRequestInfo( array $info );
 326 }