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+<?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]
+	 *  - deprecationLogger: Callback to log a deprecation warning. [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 $workCallback Work to mask ChronologyProtector writes
+	 * @param int|null &$cpIndex Position key write counter for ChronologyProtector
+	 */
+	public function shutdown(
+		$mode = self::SHUTDOWN_CHRONPROT_SYNC, callable $workCallback = null, &$cpIndex = 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 ?cpPosIndex 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 appendShutdownCPIndexAsQuery( $url, $time );
+
+	/**
+	 * @param array $info Map of fields, including:
+	 *   - IPAddress : IP address
+	 *   - UserAgent : User-Agent HTTP header
+	 *   - ChronologyProtection : cookie/header value specifying ChronologyProtector usage
+	 *   - ChronologyPositionIndex: timestamp used to get up-to-date DB positions for the agent
+	 */
+	public function setRequestInfo( array $info );
+
+	/**
+	 * Make certain table names use their own database, schema, and table prefix
+	 * when passed into SQL queries pre-escaped and without a qualified database name
+	 *
+	 * For example, "user" can be converted to "myschema.mydbname.user" for convenience.
+	 * Appearances like `user`, somedb.user, somedb.someschema.user will used literally.
+	 *
+	 * Calling this twice will completely clear any old table aliases. Also, note that
+	 * callers are responsible for making sure the schemas and databases actually exist.
+	 *
+	 * @param array[] $aliases Map of (table => (dbname, schema, prefix) map)
+	 * @since 1.31
+	 */
+	public function setTableAliases( array $aliases );
+
+	/**
+	 * Convert certain index names to alternative names before querying the DB
+	 *
+	 * Note that this applies to indexes regardless of the table they belong to.
+	 *
+	 * This can be employed when an index was renamed X => Y in code, but the new Y-named
+	 * indexes were not yet built on all DBs. After all the Y-named ones are added by the DBA,
+	 * the aliases can be removed, and then the old X-named indexes dropped.
+	 *
+	 * @param string[] $aliases
+	 * @return mixed
+	 * @since 1.31
+	 */
+	public function setIndexAliases( array $aliases );
+}