--- /dev/null
+<?php
+/**
+ * Generator and manager of database load balancing objects
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup Database
+ */
+
+namespace Wikimedia\Rdbms;
+
+use InvalidArgumentException;
+
+/**
+ * An interface for generating database load balancers
+ * @ingroup Database
+ * @since 1.28
+ */
+interface ILBFactory {
+ const SHUTDOWN_NO_CHRONPROT = 0; // don't save DB positions at all
+ const SHUTDOWN_CHRONPROT_ASYNC = 1; // save DB positions, but don't wait on remote DCs
+ const SHUTDOWN_CHRONPROT_SYNC = 2; // save DB positions, waiting on all DCs
+
+ /**
+ * Construct a manager of ILoadBalancer objects
+ *
+ * Sub-classes will extend the required keys in $conf with additional parameters
+ *
+ * @param array $conf Array with keys:
+ * - localDomain: A DatabaseDomain or domain ID string.
+ * - readOnlyReason : Reason the master DB is read-only if so [optional]
+ * - srvCache : BagOStuff object for server cache [optional]
+ * - memStash : BagOStuff object for cross-datacenter memory storage [optional]
+ * - wanCache : WANObjectCache object [optional]
+ * - hostname : The name of the current server [optional]
+ * - cliMode: Whether the execution context is a CLI script. [optional]
+ * - profiler : Class name or instance with profileIn()/profileOut() methods. [optional]
+ * - trxProfiler: TransactionProfiler instance. [optional]
+ * - replLogger: PSR-3 logger instance. [optional]
+ * - connLogger: PSR-3 logger instance. [optional]
+ * - queryLogger: PSR-3 logger instance. [optional]
+ * - perfLogger: PSR-3 logger instance. [optional]
+ * - errorLogger : Callback that takes an Exception and logs it. [optional]
+ * @throws InvalidArgumentException
+ */
+ public function __construct( array $conf );
+
+ /**
+ * Disables all load balancers. All connections are closed, and any attempt to
+ * open a new connection will result in a DBAccessError.
+ * @see ILoadBalancer::disable()
+ */
+ public function destroy();
+
+ /**
+ * Create a new load balancer object. The resulting object will be untracked,
+ * not chronology-protected, and the caller is responsible for cleaning it up.
+ *
+ * This method is for only advanced usage and callers should almost always use
+ * getMainLB() instead. This method can be useful when a table is used as a key/value
+ * store. In that cases, one might want to query it in autocommit mode (DBO_TRX off)
+ * but still use DBO_TRX transaction rounds on other tables.
+ *
+ * @param bool|string $domain Domain ID, or false for the current domain
+ * @return ILoadBalancer
+ */
+ public function newMainLB( $domain = false );
+
+ /**
+ * Get a cached (tracked) load balancer object.
+ *
+ * @param bool|string $domain Domain ID, or false for the current domain
+ * @return ILoadBalancer
+ */
+ public function getMainLB( $domain = false );
+
+ /**
+ * Create a new load balancer for external storage. The resulting object will be
+ * untracked, not chronology-protected, and the caller is responsible for cleaning it up.
+ *
+ * This method is for only advanced usage and callers should almost always use
+ * getExternalLB() instead. This method can be useful when a table is used as a
+ * key/value store. In that cases, one might want to query it in autocommit mode
+ * (DBO_TRX off) but still use DBO_TRX transaction rounds on other tables.
+ *
+ * @param string $cluster External storage cluster name
+ * @return ILoadBalancer
+ */
+ public function newExternalLB( $cluster );
+
+ /**
+ * Get a cached (tracked) load balancer for external storage
+ *
+ * @param string $cluster External storage cluster name
+ * @return ILoadBalancer
+ */
+ public function getExternalLB( $cluster );
+
+ /**
+ * Get cached (tracked) load balancers for all main database clusters
+ *
+ * @return LoadBalancer[] Map of (cluster name => LoadBalancer)
+ * @since 1.29
+ */
+ public function getAllMainLBs();
+
+ /**
+ * Get cached (tracked) load balancers for all external database clusters
+ *
+ * @return LoadBalancer[] Map of (cluster name => LoadBalancer)
+ * @since 1.29
+ */
+ public function getAllExternalLBs();
+
+ /**
+ * Execute a function for each tracked load balancer
+ * The callback is called with the load balancer as the first parameter,
+ * and $params passed as the subsequent parameters.
+ *
+ * @param callable $callback
+ * @param array $params
+ */
+ public function forEachLB( $callback, array $params = [] );
+
+ /**
+ * Prepare all tracked load balancers for shutdown
+ * @param int $mode One of the class SHUTDOWN_* constants
+ * @param callable|null $workCallback Work to mask ChronologyProtector writes
+ */
+ public function shutdown(
+ $mode = self::SHUTDOWN_CHRONPROT_SYNC, callable $workCallback = null
+ );
+
+ /**
+ * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot
+ *
+ * @param string $fname Caller name
+ */
+ public function flushReplicaSnapshots( $fname = __METHOD__ );
+
+ /**
+ * Commit open transactions on all connections. This is useful for two main cases:
+ * - a) To commit changes to the masters.
+ * - b) To release the snapshot on all connections, master and replica DBs.
+ * @param string $fname Caller name
+ * @param array $options Options map:
+ * - maxWriteDuration: abort if more than this much time was spent in write queries
+ */
+ public function commitAll( $fname = __METHOD__, array $options = [] );
+
+ /**
+ * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set)
+ *
+ * The DBO_TRX setting will be reverted to the default in each of these methods:
+ * - commitMasterChanges()
+ * - rollbackMasterChanges()
+ * - commitAll()
+ *
+ * This allows for custom transaction rounds from any outer transaction scope.
+ *
+ * @param string $fname
+ * @throws DBTransactionError
+ */
+ public function beginMasterChanges( $fname = __METHOD__ );
+
+ /**
+ * Commit changes on all master connections
+ * @param string $fname Caller name
+ * @param array $options Options map:
+ * - maxWriteDuration: abort if more than this much time was spent in write queries
+ * @throws DBTransactionError
+ */
+ public function commitMasterChanges( $fname = __METHOD__, array $options = [] );
+
+ /**
+ * Rollback changes on all master connections
+ * @param string $fname Caller name
+ */
+ public function rollbackMasterChanges( $fname = __METHOD__ );
+
+ /**
+ * Check if a transaction round is active
+ * @return bool
+ * @since 1.29
+ */
+ public function hasTransactionRound();
+
+ /**
+ * Determine if any master connection has pending changes
+ * @return bool
+ */
+ public function hasMasterChanges();
+
+ /**
+ * Detemine if any lagged replica DB connection was used
+ * @return bool
+ */
+ public function laggedReplicaUsed();
+
+ /**
+ * Determine if any master connection has pending/written changes from this request
+ * @param float $age How many seconds ago is "recent" [defaults to LB lag wait timeout]
+ * @return bool
+ */
+ public function hasOrMadeRecentMasterChanges( $age = null );
+
+ /**
+ * Waits for the replica DBs to catch up to the current master position
+ *
+ * Use this when updating very large numbers of rows, as in maintenance scripts,
+ * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs.
+ *
+ * By default this waits on all DB clusters actually used in this request.
+ * This makes sense when lag being waiting on is caused by the code that does this check.
+ * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
+ * that were not changed since the last wait check. To forcefully wait on a specific cluster
+ * for a given domain, use the 'domain' parameter. To forcefully wait on an "external" cluster,
+ * use the "cluster" parameter.
+ *
+ * Never call this function after a large DB write that is *still* in a transaction.
+ * It only makes sense to call this after the possible lag inducing changes were committed.
+ *
+ * @param array $opts Optional fields that include:
+ * - domain : wait on the load balancer DBs that handles the given domain ID
+ * - cluster : wait on the given external load balancer DBs
+ * - timeout : Max wait time. Default: ~60 seconds
+ * - ifWritesSince: Only wait if writes were done since this UNIX timestamp
+ * @throws DBReplicationWaitError If a timeout or error occurred waiting on a DB cluster
+ */
+ public function waitForReplication( array $opts = [] );
+
+ /**
+ * Add a callback to be run in every call to waitForReplication() before waiting
+ *
+ * Callbacks must clear any transactions that they start
+ *
+ * @param string $name Callback name
+ * @param callable|null $callback Use null to unset a callback
+ */
+ public function setWaitForReplicationListener( $name, callable $callback = null );
+
+ /**
+ * Get a token asserting that no transaction writes are active
+ *
+ * @param string $fname Caller name (e.g. __METHOD__)
+ * @return mixed A value to pass to commitAndWaitForReplication()
+ */
+ public function getEmptyTransactionTicket( $fname );
+
+ /**
+ * Convenience method for safely running commitMasterChanges()/waitForReplication()
+ *
+ * This will commit and wait unless $ticket indicates it is unsafe to do so
+ *
+ * @param string $fname Caller name (e.g. __METHOD__)
+ * @param mixed $ticket Result of getEmptyTransactionTicket()
+ * @param array $opts Options to waitForReplication()
+ * @throws DBReplicationWaitError
+ */
+ public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] );
+
+ /**
+ * @param string $dbName DB master name (e.g. "db1052")
+ * @return float|bool UNIX timestamp when client last touched the DB or false if not recent
+ */
+ public function getChronologyProtectorTouched( $dbName );
+
+ /**
+ * Disable the ChronologyProtector for all load balancers
+ *
+ * This can be called at the start of special API entry points
+ */
+ public function disableChronologyProtection();
+
+ /**
+ * Set a new table prefix for the existing local domain ID for testing
+ *
+ * @param string $prefix
+ */
+ public function setDomainPrefix( $prefix );
+
+ /**
+ * Close all open database connections on all open load balancers.
+ */
+ public function closeAll();
+
+ /**
+ * @param string $agent Agent name for query profiling
+ */
+ public function setAgentName( $agent );
+
+ /**
+ * Append ?cpPosTime parameter to a URL for ChronologyProtector purposes if needed
+ *
+ * Note that unlike cookies, this works accross domains
+ *
+ * @param string $url
+ * @param float $time UNIX timestamp just before shutdown() was called
+ * @return string
+ */
+ public function appendPreShutdownTimeAsQuery( $url, $time );
+
+ /**
+ * @param array $info Map of fields, including:
+ * - IPAddress : IP address
+ * - UserAgent : User-Agent HTTP header
+ * - ChronologyProtection : cookie/header value specifying ChronologyProtector usage
+ */
+ public function setRequestInfo( array $info );
+}
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