LoadBalancer manager for sites with one "main" cluster using only injected database connections. More...

Inherits Wikimedia\Rdbms\LBFactory.

Collaboration diagram for Wikimedia\Rdbms\LBFactorySingle:

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Public Member Functions

__construct (array $conf)

__destruct ()

getAllExternalLBs ()

Get the tracked load balancer instances for all external clusters.

getAllMainLBs ()

Get the tracked load balancer instances for all main clusters.

getExternalLB ( $cluster)

Get the tracked load balancer instance for an external cluster.If no tracked instances exists, then one will be instantiated

Parameters

string $cluster External cluster name

Exceptions

InvalidArgumentException If $cluster is not recognized

Returns: ILoadBalancer

getMainLB ( $domain=false)

Get the tracked load balancer instance for the main cluster that handles the given domain.If no tracked instances exists, then one will be instantiated

Note: The local/default database domain used by the load balancer instance will still inherit from this ILBFactory instance, regardless of the $domain parameter.

Parameters

string | false $domain Domain ID, or false for the current domain

Returns: ILoadBalancer

newExternalLB ( $cluster)

Create a new load balancer instance for an external cluster.The resulting object will be untracked and the caller is responsible for cleaning it up. Database replication positions will not be saved by ChronologyProtector.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.

Parameters

string $cluster External cluster name

Exceptions

InvalidArgumentException If $cluster is not recognized

Returns: ILoadBalancerForOwner

newMainLB ( $domain=false)

Create a new load balancer instance for the main cluster that handles the given domain.The resulting object is considered to be owned by the caller. Namely, it will be untracked, the caller is responsible for cleaning it up, and replication positions from it will not be saved by ChronologyProtector.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.

Note: The local/default database domain used by the load balancer instance will still inherit from this ILBFactory instance, regardless of the $domain parameter.

Parameters

string | false $domain Domain ID, or false for the current domain

Returns: ILoadBalancerForOwner

Public Member Functions inherited from Wikimedia\Rdbms\LBFactory

autoReconfigure ()

Reload config using the callback passed defined $config['configCallback'].

beginPrimaryChanges ( $fname=__METHOD__)

Wrap subsequent queries for all transaction round aware primary connections in a transaction.Each of these transactions will be owned by this ILBFactory instance such that direct calls to IDatabase::commit() or IDatabase::rollback() will be disabled. These transactions get resolved by a single call to either commitPrimaryChanges() or rollbackPrimaryChanges(), after which, the transaction wrapping and ownership behavior revert back to the default. When there are multiple connections involved, these methods perform best-effort distributed transactions. When using distributed transactions, the RDBMS should be configured to used pessimistic concurrency control such that the commit step of each transaction is unlikely to fail.Transactions on replication connections are flushed so that future reads will not keep using the same point-in-time view snapshots (e.g. from MySQL REPEATABLE-READ). However, this does not wait for replication to catch up, so subsequent reads from replicas might not reflect recently committed changes.This only applies to the tracked load balancer instances.This allows for custom transaction rounds from any outer transaction scope.

Parameters

string $fname

Exceptions

DBTransactionError

Since: 1.37

closeAll ( $fname=__METHOD__)

Close all connections on instantiated tracked load balancer instances.

Parameters

string $fname Caller name (e.g. METHOD)

commitAndWaitForReplication ( $fname, $ticket, array $opts=[])

Commit primary DB transactions and wait for replication (if $ticket indicates it is safe).This is mostly used in jobs or deferred updates dealing with batching.The ticket is used to check that the caller owns the transaction round or can act on behalf of the caller that owns the transaction round.

See also: ILBFactory::commitPrimaryChanges(); ILBFactory::waitForReplication()

Since: 1.28

Parameters

string	$fname	Caller name (e.g. METHOD)
mixed	$ticket	Result of getEmptyTransactionTicket()
array	$opts	Options to waitForReplication()

Returns: bool True if the wait was successful, false on timeout

commitPrimaryChanges ( $fname=__METHOD__, int $maxWriteDuration=0)

Commit all primary connection transactions and flush all replica connection transactions.Transactions on replication connections are flushed so that future reads will not keep using the same point-in-time view snapshots (e.g. from MySQL REPEATABLE-READ). However, this does not wait for replication to catch up, so subsequent reads from replicas might not reflect the committed changes.This only applies to the instantiated tracked load balancer instances.

Parameters

string	$fname	Caller name
int	$maxWriteDuration	abort if more than this much time was spent in write queries

Exceptions

DBTransactionError

Since: 1.37

destroy ()

Close all connections and make further attempts to open connections result in DBAccessError.

disableChronologyProtection ()

Disable the ChronologyProtector on all instantiated tracked load balancer instances.

flushPrimarySessions ( $fname=__METHOD__)

Release important session-level state (named lock, table locks) as post-rollback cleanup.This only applies to the instantiated tracked load balancer instances.This should only be called by application entry point functions, since there must be no chance that a future caller will still be expecting some of the lost session state.

Parameters

string $fname Caller name

Since: 1.38

flushReplicaSnapshots ( $fname=__METHOD__)

Commit all replica database server transactions, clearing any point-in-time view snapshots.This only applies to the instantiated tracked load balancer instances.This is useful for getting rid of stale data from an implicit transaction round

Parameters

string $fname Caller name

Deprecated: Since 1.43

getAllLBs ()

Get all tracked load balancer instances (generator)

Returns: Generator|ILoadBalancer[]

Since: 1.39

getAutoCommitPrimaryConnection ( $domain=false)

Like IConnectionProvider::getPrimaryDatabase() but with AUTOCOMMIT mode.This is useful for whether the caller needs to use AUTOCOMMIT (no transaction wrapping) or it needs a new connection outside of the current transaction to bypass REPEATABLE READ isolation.This method accepts virtual domains ({

See also: \MediaWiki\MainConfigSchema::VirtualDomainsMapping}).

Since: 1.44

Parameters

string | false $domain Domain ID, or false for the current domain

Returns: IDatabase

getEmptyTransactionTicket ( $fname)

Get a token asserting that no write transactions are active on tracked connections.This is mostly used in jobs or deferred updates dealing with batching.

Since: 1.28

Parameters

string $fname Caller name (e.g. METHOD)

Returns: mixed A value to pass to commitAndWaitForReplication()

getLoadBalancer ( $domain=false)

Get the tracked load balancer instance for a given domain.If no tracked instances exists, then one will be instantiated.This method accepts virtual domains ({

See also: \MediaWiki\MainConfigSchema::VirtualDomainsMapping}).

Since: 1.43

Parameters

string | false $domain Domain ID, or false for the current domain

Returns: ILoadBalancer

getLocalDomainID ()

Get the local (and default) database domain ID of connection handles.

getMappedDomain (string|false $domain)

getPrimaryDatabase ( $domain=false)

Get connection to the primary database.This should be used when there the code needs to write to the database.This method accepts virtual domains ({

See also: \MediaWiki\MainConfigSchema::VirtualDomainsMapping}).

Since: 1.40

Parameters

string | false $domain Domain ID, or false for the current domain

Returns: IDatabase

getReplicaDatabase (string|false $domain=false, $group=null)

Get connection to a replica database.Note that a read can have replication lag.This method accepts virtual domains ({

See also: \MediaWiki\MainConfigSchema::VirtualDomainsMapping}).

Since: 1.40

Parameters

string \| false	$domain	Domain ID, or false for the current domain
string \| null	$group	Query group; null for the default group

Returns: IReadableDatabase

getTransactionProfiler ()

Get the TransactionProfiler used by this instance.

Returns: TransactionProfiler

Since: 1.35

hasOrMadeRecentPrimaryChanges ( $age=null)

Determine if any primary connection has pending/written changes from this request.This only applies to the instantiated tracked load balancer instances.

Parameters

float | null $age How many seconds ago is "recent" [defaults to LB lag wait timeout]

Returns: bool

hasPrimaryChanges ()

Determine if any primary connection has pending changes.This only applies to the instantiated tracked load balancer instances.

Returns: bool

Since: 1.37

hasStreamingReplicaServers ()

Whether it has streaming replica servers.

Since: 1.41

Returns: bool

hasTransactionRound ()

Check if an explicit transaction round is active.

Returns: bool

Since: 1.29

isLocalDomain ( $domain)

Determine whether, after mapping, the domain refers to the main domain of the local wiki.

isReadyForRoundOperations ()

Check if transaction rounds can be started, committed, or rolled back right now.This can be used as a recursion guard to avoid exceptions in transaction callbacks.

Returns: bool

Since: 1.32

isSharedVirtualDomain ( $domain)

Is the domain a virtual domain with a statically configured database name?

laggedReplicaUsed ()

Determine if any lagged replica database server connection was used.This only applies to the instantiated tracked load balancer instances.

Returns: bool

reconfigure (array $conf)

Reconfigure using the given config array.

redefineLocalDomain ( $domain)

Close all connections and redefine the local database domain.This only applies to the tracked load balancer instances.This method is only intended for use with schema creation or integration testing

Parameters

DatabaseDomain | string $domain

Since: 1.33

rollbackPrimaryChanges ( $fname=__METHOD__)

Rollback all primary connection transactions and flush all replica connection transactions.This only applies to the instantiated tracked load balancer instances.

Parameters

string $fname Caller name

Since: 1.37

setAgentName ( $agent)

Parameters

string $agent Agent name for query profiling

setDefaultGroupName (string $defaultGroup)

Set the default group name for all load balancers.

setDefaultReplicationWaitTimeout ( $seconds)

Set the default timeout for replication wait checks.

Parameters

int $seconds Timeout, in seconds

Returns: int The previous default timeout

Since: 1.35

setDomainAliases (array $aliases)

Convert certain database domains to alternative ones.This can be used for backwards compatibility logic.

Parameters

DatabaseDomain[] | string[] $aliases Map of (domain alias => domain)

Since: 1.35

setLocalDomainPrefix ( $prefix)

Set a new table prefix for the existing local domain ID for testing.

Parameters

string $prefix

Since: 1.33

setTableAliases (array $aliases)

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.

Parameters

array[] $aliases Map of (table => (dbname, schema, prefix) map)

Since: 1.31

setWaitForReplicationListener ( $name, ?callable $callback=null)

Add a callback to be run in every call to waitForReplication() prior to any waiting.Callbacks must clear any transactions that they start.

Parameters

string	$name	Callback name
callable \| null	$callback	Use null to unset a callback

Deprecated: Since 1.44

shutdown ( $flags=self::SHUTDOWN_NORMAL, ?callable $workCallback=null, &$cpIndex=null, &$cpClientId=null)

Prepare all instantiated tracked load balancer instances for shutdown.

Parameters

int	$flags	Bit field of ILBFactory::SHUTDOWN_* constants
callable \| null	$workCallback	Work to mask ChronologyProtector writes
int \| null	&$cpIndex	Position key write counter for ChronologyProtector [returned]
string \| null	&$cpClientId	Client ID hash for ChronologyProtector [returned]

waitForReplication (array $opts=[])

Waits for the replica database server to catch up to the current primary position.Use this when updating very large numbers of rows, as in maintenance scripts, to avoid causing too much lag. This is a no-op if there are no replica database servers.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.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.This only applies to the instantiated tracked load balancer instances.

Parameters

array

$opts

Optional fields that include:

timeout: Max wait time. Default: 60 seconds for CLI, 1 second for web.
ifWritesSince: Only wait if writes were done since this UNIX timestamp.

Returns: bool True on success, false if a timeout or error occurred while waiting

Static Public Member Functions
static	newDisabled (array $params=[])

static	newFromConnection (IDatabase $db, array $params=[])

Protected Member Functions
	getLBsForOwner ()
	Get all tracked load balancers with the internal "for owner" interface. Returns Generator\|ILoadBalancerForOwner[]

Protected Member Functions inherited from Wikimedia\Rdbms\LBFactory
	baseLoadBalancerParams ()
	Get parameters to ILoadBalancer::__construct()

	configure (array $conf)

	initLoadBalancer (ILoadBalancerForOwner $lb)

Additional Inherited Members
Public Attributes inherited from Wikimedia\Rdbms\ILBFactory
const	CLUSTER_MAIN_DEFAULT = 'DEFAULT'
	Default main cluster name (do not change this)

const	SHUTDOWN_NO_CHRONPROT = 1
	Do not save "session consistency" DB replication positions.

const	SHUTDOWN_NORMAL = 0
	Idiom for "no special shutdown flags".

Protected Attributes inherited from Wikimedia\Rdbms\LBFactory
ChronologyProtector	$chronologyProtector

DatabaseDomain[] string[]	$domainAliases = []
	Map of (domain alias => DB domain)

DatabaseDomain	$localDomain
	Local domain.

string false	$readOnlyReason = false
	Reason all LBs are read-only or false if not.

BagOStuff	$srvCache

array string[]	$virtualDomains = []
	List of registered virtual domains.

array array[]	$virtualDomainsMapping = []
	Map of virtual domain to array of cluster and domain.

WANObjectCache	$wanCache

Detailed Description

LoadBalancer manager for sites with one "main" cluster using only injected database connections.

This class assumes that there are no "external" clusters.

LoadBalancerDisabled will be used if a null connection handle is injected.

See also: ILBFactory

Definition at line 21 of file LBFactorySingle.php.

Constructor & Destructor Documentation

◆ __construct()

Wikimedia\Rdbms\LBFactorySingle::__construct ( array $conf )

Note: Use of newFromConnection is preferable

Parameters

array

$conf

An associative array containing one of the following:

connection: The IDatabase connection handle to use; null to disable access

Reimplemented from Wikimedia\Rdbms\LBFactory.

Definition at line 31 of file LBFactorySingle.php.

References Wikimedia\Rdbms\LBFactory\baseLoadBalancerParams(), and Wikimedia\Rdbms\LBFactory\initLoadBalancer().

◆ __destruct()

Wikimedia\Rdbms\LBFactorySingle::__destruct ( )

Definition at line 114 of file LBFactorySingle.php.

Member Function Documentation

◆ getAllExternalLBs()

Wikimedia\Rdbms\LBFactorySingle::getAllExternalLBs ( )

Get the tracked load balancer instances for all external clusters.

If no tracked instance exists for a cluster, then one will be instantiated

Returns: ILoadBalancer[] Map of (cluster name => ILoadBalancer)

Since: 1.29

Implements Wikimedia\Rdbms\ILBFactory.

Definition at line 103 of file LBFactorySingle.php.

◆ getAllMainLBs()

Wikimedia\Rdbms\LBFactorySingle::getAllMainLBs ( )

Get the tracked load balancer instances for all main clusters.

If no tracked instance exists for a cluster, then one will be instantiated

Note that default main cluster name is ILoadBalancer::CLUSTER_MAIN_DEFAULT

Returns: ILoadBalancer[] Map of (cluster name => ILoadBalancer)

Since: 1.29

Implements Wikimedia\Rdbms\ILBFactory.

Definition at line 99 of file LBFactorySingle.php.

◆ getExternalLB()

Wikimedia\Rdbms\LBFactorySingle::getExternalLB ( $cluster )

Get the tracked load balancer instance for an external cluster.If no tracked instances exists, then one will be instantiated

Parameters

string $cluster External cluster name

Exceptions

InvalidArgumentException If $cluster is not recognized

Returns: ILoadBalancer

Implements Wikimedia\Rdbms\ILBFactory.

Definition at line 94 of file LBFactorySingle.php.

◆ getLBsForOwner()

Wikimedia\Rdbms\LBFactorySingle::getLBsForOwner ( )

protected

Get all tracked load balancers with the internal "for owner" interface.

Returns: Generator|ILoadBalancerForOwner[]

Reimplemented from Wikimedia\Rdbms\LBFactory.

Definition at line 108 of file LBFactorySingle.php.

◆ getMainLB()

Wikimedia\Rdbms\LBFactorySingle::getMainLB ( $domain = false )

Get the tracked load balancer instance for the main cluster that handles the given domain.If no tracked instances exists, then one will be instantiated

Note: The local/default database domain used by the load balancer instance will still inherit from this ILBFactory instance, regardless of the $domain parameter.

Parameters

string | false $domain Domain ID, or false for the current domain

Returns: ILoadBalancer

Implements Wikimedia\Rdbms\ILBFactory.

Definition at line 83 of file LBFactorySingle.php.

◆ newDisabled()

static Wikimedia\Rdbms\LBFactorySingle::newDisabled ( array $params = [] )

static

Parameters

array $params Parameter map to LBFactorySingle::__construct()

Since: 1.40

Definition at line 69 of file LBFactorySingle.php.

◆ newExternalLB()

Wikimedia\Rdbms\LBFactorySingle::newExternalLB ( $cluster )

Create a new load balancer instance for an external cluster.The resulting object will be untracked and the caller is responsible for cleaning it up. Database replication positions will not be saved by ChronologyProtector.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.

Parameters

string $cluster External cluster name

Exceptions

InvalidArgumentException If $cluster is not recognized

Returns: ILoadBalancerForOwner

Implements Wikimedia\Rdbms\ILBFactory.

Definition at line 88 of file LBFactorySingle.php.

◆ newFromConnection()

static Wikimedia\Rdbms\LBFactorySingle::newFromConnection	(	IDatabase	$db,
		array	$params = [] )

static

Parameters

IDatabase	$db	Live connection handle
array	$params	Parameter map to LBFactorySingle::__construct()

Since: 1.28

Definition at line 57 of file LBFactorySingle.php.

◆ newMainLB()

Wikimedia\Rdbms\LBFactorySingle::newMainLB ( $domain = false )

Create a new load balancer instance for the main cluster that handles the given domain.The resulting object is considered to be owned by the caller. Namely, it will be untracked, the caller is responsible for cleaning it up, and replication positions from it will not be saved by ChronologyProtector.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.

Note: The local/default database domain used by the load balancer instance will still inherit from this ILBFactory instance, regardless of the $domain parameter.

Parameters

string | false $domain Domain ID, or false for the current domain

Returns: ILoadBalancerForOwner

Implements Wikimedia\Rdbms\ILBFactory.

Definition at line 77 of file LBFactorySingle.php.

The documentation for this class was generated from the following file:

includes/libs/Rdbms/LBFactory/LBFactorySingle.php

Public Member Functions

Static Public Member Functions

Protected Member Functions

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ __construct()

◆ __destruct()

Member Function Documentation

◆ getAllExternalLBs()

◆ getAllMainLBs()

◆ getExternalLB()

◆ getLBsForOwner()

◆ getMainLB()

◆ newDisabled()

◆ newExternalLB()

◆ newFromConnection()

◆ newMainLB()