This class is a delegate to ILBFactory for a given database cluster. More...

Inherited by Wikimedia\Rdbms\ILoadBalancerForOwner.

Public Member Functions
	explicitTrxActive ()
	Determine whether an explicit transaction is active on any open primary connection.

	getClusterName ()
	Get the name of the overall cluster of database servers managing the dataset.

	getConnection ( $i, $groups=[], $domain=false, $flags=0)
	Get a lazy-connecting database handle for a specific or virtual (DB_PRIMARY/DB_REPLICA) server index.

	getConnectionInternal ( $i, $groups=[], $domain=false, $flags=0)

	getConnectionRef ( $i, $groups=[], $domain=false, $flags=0)

	getLagTimes ()
	Get an estimate of replication lag (in seconds) for each server.

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

	getMaintenanceConnectionRef ( $i, $groups=[], $domain=false, $flags=0)
	Get a DB handle, suitable for migrations and schema changes, for a server index.

	getMaxLag ()
	Get the name and lag time of the most-lagged replica server.

	getPrimaryPos ()
	Get the current primary replication position.

	getReaderIndex ( $group=false)
	Get the specific server index of the reader connection for a given group.

	getReadOnlyReason ()

	getServerAttributes ( $i)
	Get basic attributes of the server with the specified index without connecting.

	getServerConnection ( $i, $domain, $flags=0)
	Get a DB handle for a specific server index.

	getServerCount ()
	Get the number of servers defined in configuration.

	getServerInfo ( $i)
	Return the server configuration map for the server with the specified index.

	getServerName ( $i)
	Get the readable name of the server with the specified index.

	getServerType ( $i)
	Get the RDBMS type of the server with the specified index (e.g.

	hasOrMadeRecentPrimaryChanges ( $age=null)
	Check if this load balancer object had any recent or still pending writes issued against it by this PHP thread.

	hasPrimaryChanges ()
	Whether there are pending changes or callbacks in a transaction by this thread.

	hasReplicaServers ()
	Whether there are any replica servers configured.

	hasStreamingReplicaServers ()
	Whether any replica servers use streaming replication from the primary server.

	pingAll ()

	resolveDomainID ( $domain)

	setDomainAliases (array $aliases)
	Convert certain database domains to alternative ones.

	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.

	setTempTablesOnlyMode ( $value, $domain)
	Indicate whether the tables on this domain are only temporary tables for testing.

	setTransactionListener ( $name, ?callable $callback=null)
	Set a callback via IDatabase::setTransactionListener() on all current and future primary connections of this load balancer.

	waitForPrimaryPos (IDatabase $conn)
	Wait for a replica DB to reach a specified primary position.

Public Attributes
const	CONN_SILENCE_ERRORS = 4
	Yield null on connection failure instead of throwing an exception.

const	CONN_TRX_AUTOCOMMIT = 1
	Yield a tracked autocommit-mode handle (reuse existing ones)

const	CONN_UNTRACKED_GAUGE = 2
	Yield an untracked, low-timeout, autocommit-mode handle (to gauge server health)

const	DB_PRIMARY = -2
	Request a primary, write-enabled DB connection.

const	DB_REPLICA = -1
	Request a replica DB connection.

const	DOMAIN_ANY = ''
	Domain specifier when no specific database needs to be selected.

const	GROUP_GENERIC = ''
	The generic query group.

Detailed Description

This class is a delegate to ILBFactory for a given database cluster.

ILoadBalancer tracks the database connections and transactions for a given database cluster. A "cluster" is considered to be the set of database servers that manage a given dataset. Within a given cluster, each database server can have one of the following roles:

sole-primary: the server used by this datacenter for writes from the application
co-primary: one of several servers used by this datacenter for writes from the application, relying on asynchronous replication to synchronize their copies of the dataset
replica: a server used only for reads from the application, relying on asynchronous replication to apply writes from the primary server or co-primary servers
static clone: a server that only accepts reads from the application, does not replicate, and has a copy of the final dataset, which must be static (all the servers reject writes)

Single-datacenter database clusters consist of either:

A sole-primary server and zero or more replica servers
A set of static clone servers

Multi-datacenter database clusters either consist of either:

A sole-primary server and zero or more replica servers in the "primary datacenter" (the one datacenter meant to handle requests/jobs that mutate the database), and zero or more replica servers in each "secondary datacenter" (all the other datacenters)
A co-primary server and zero or more replica servers within each datacenter
A set of static clone servers in each datacenter

The term "primary" refers to the server used by this datacenter for handling writes, whether it is a sole-primary or co-primary.

The "servers" configuration array contains the list of database servers to use for operations originating from the the local datacenter. The first entry must refer to the server to use for write and read-for-write operations (e.g. the "writer server"):

If there is a primary server, then the first entry must refer to it, even if the primary server resides in a remote datacenter
If there are co-primary servers, then the first entry must refer to the one in the local datacenter
If the servers are static clones, then the first entry can refer to any of them, since the concept of a "writer server" is merely nominal

On an infrastructure level, circular replication setups can have more than one database server act as a replication "source" within the same datacenter, provided that no more than one of the servers are writable at any time, namely the "writer server". The other source servers will be treated as replicas by the load balancer, but can be quickly promoted to the "writer server" by the site admin as needed.

Likewise, Galera Cluster setups still require the choice of a single "writer server" for each datacenter. Limiting the number of servers that initiate transactions helps reduce the rate of aborted transactions due to wsrep conflicts.

By default, each DB server uses DBO_DEFAULT for its 'flags' setting, unless explicitly set otherwise in configuration. DBO_DEFAULT behavior depends on whether 'cliMode' is set:

In CLI mode, the flag has no effect with regards to LoadBalancer.
In non-CLI mode, the flag causes implicit transactions to be used; the first query on a database starts a transaction on that database. The transactions are meant to remain pending until either commitPrimaryChanges() or rollbackPrimaryChanges() is called. The application must have some point where it calls commitPrimaryChanges() near the end of the PHP request. Every iteration of beginPrimaryChanges()/commitPrimaryChanges() is called a "transaction round". Rounds are useful on the primary DB connections because they make single-DB (and by and large multi-DB) updates in web requests all-or-nothing. Also, transactions on replica DBs are useful when REPEATABLE-READ or SERIALIZABLE isolation is used because all foreign keys and constraints hold across separate queries in the DB transaction since the data appears within a consistent point-in-time snapshot.

The typical caller will use LoadBalancer::getConnection( DB_* ) to yield a database connection handle. The choice of which DB server to use is based on pre-defined loads for weighted random selection, adjustments thereof by LoadMonitor, and the amount of replication lag on each DB server. Lag checks might cause problems in certain setups, so they should be tuned in the server configuration maps as follows:

Sole-primary + N Replica(s): set 'max lag' to an appropriate threshold for avoiding any replica database lagged by this much or more. If all replicas are this lagged, then the load balancer considers the cluster to be read-only.
Per-datacenter co-primary + N Replica(s): set 'max lag' to an appropriate threshold for avoiding any replica database lagged by this much or more. If all replicas are this lagged, then the load balancer considers the cluster to be read-only.
Read-only archive clones: set 'is static' in the server configuration maps. This will treat all such DBs as having 0 lag.
Externally updated dataset clones: set 'is static' in the server configuration maps. This will treat all such DBs as having 0 lag.
SQL load balancing proxy: any proxy should handle lag checks on its own, so the 'max lag' parameter should probably be set to INF in the server configuration maps. This will make the load balancer ignore whatever it detects as the lag of the logical replica is (which would probably just randomly bounce around).

If using a SQL proxy service, it would probably be best to have two proxy hosts for the load balancer to talk to. One would be the 'host' of the "writer server" entry and another for the (logical) replica server entry. The proxy could map the load balancer's "replica" DB to any number of physical replica DBs.

Since: 1.28

Definition at line 113 of file ILoadBalancer.php.

Member Function Documentation

◆ explicitTrxActive()

Wikimedia\Rdbms\ILoadBalancer::explicitTrxActive ( )

Determine whether an explicit transaction is active on any open primary connection.

Returns: bool

Since: 1.39

Implemented in Wikimedia\Rdbms\LoadBalancer.

◆ getClusterName()

Wikimedia\Rdbms\ILoadBalancer::getClusterName ( )

Get the name of the overall cluster of database servers managing the dataset.

Note that the cluster might contain servers in multiple datacenters. The load balancer instance only needs to be aware of the local replica servers, along with either the sole-primary server or the local co-primary server.

This is useful for identifying a cluster or replicated dataset, even when:

The primary server is sometimes swapped with another one
The cluster/dataset is replicated among multiple datacenters, with one "primary" datacenter having the writable primary server and the other datacenters having a read-only replica in the "primary" server slot
The dataset is replicated among multiple datacenters, via circular replication, with each datacenter having its own "co-primary" server

Returns: string

Since: 1.36

Implemented in Wikimedia\Rdbms\LoadBalancer.

Referenced by Wikimedia\Rdbms\ChronologyProtector\getSessionPrimaryPos(), Wikimedia\Rdbms\ChronologyProtector\getTouched(), and Wikimedia\Rdbms\ChronologyProtector\stageSessionPrimaryPos().

◆ getConnection()

Wikimedia\Rdbms\ILoadBalancer::getConnection	(	$i,
		$groups = [],
		$domain = false,
		$flags = 0 )

Get a lazy-connecting database handle for a specific or virtual (DB_PRIMARY/DB_REPLICA) server index.

The server index, $i, can be one of the following:

DB_REPLICA: a server index will be selected by the load balancer based on read weight, connectivity, and replication lag. Note that the primary server might be configured with read weight. If $groups is empty then it means "the generic group", in which case all servers defined with read weight will be considered. Additional query groups can be configured, having their own list of server indexes and read weights. If a query group list is provided in $groups, then each recognized group will be tried, left-to-right, until server index selection succeeds or all groups have been tried, in which case the generic group will be tried.
DB_PRIMARY: the primary server index will be used; the same as ServerInfo::WRITER_INDEX. The value of $groups should be [] when using this server index.
Specific server index: a positive integer can be provided to use the server with that index. An error will be thrown in no such server index is recognized. This server selection method is usually only useful for internal load balancing logic. The value of $groups should be [] when using a specific server index.

Handle sharing is very useful when callers get DB_PRIMARY handles that are transaction round aware (the default). All such callers will operate within a single transaction as a consequence. The same applies to DB_REPLICA that are samely query grouped (the default) and transaction round aware (the default).

Use CONN_TRX_AUTOCOMMIT to use a separate pool of only autocommit handles. This flag is ignored for databases with ATTR_DB_LEVEL_LOCKING (e.g. sqlite) in order to avoid deadlocks. getServerAttributes() can be used to check this attribute beforehand. Avoid using begin() and commit() on such handles. If handle methods like startAtomic() and endAtomic() must be used on the handles, callers should at least make sure that the atomic sections are closed on failure via try/catch and cancelAtomic().

Use CONN_UNTRACKED_GAUGE to get a new, untracked, handle, that uses a low connection timeout, a low read timeout, and autocommit mode. This flag is intended for use only be internal callers.

CONN_UNTRACKED_GAUGE and CONN_TRX_AUTOCOMMIT are incompatible.

See also: ILoadBalancer::getServerAttributes()

Parameters

int	$i	Specific (overrides $groups) or virtual (DB_PRIMARY/DB_REPLICA) server index
string[] \| string	$groups	Query group(s) in preference order; [] for the default group
string \| false	$domain	DB domain ID or false for the local domain
int	$flags	Bitfield of CONN_* class constants

Returns: IDatabase|false This returns false on failure if CONN_SILENCE_ERRORS is set

Implemented in Wikimedia\Rdbms\LoadBalancer, and Wikimedia\Rdbms\LoadBalancerDisabled.

Referenced by MediaWiki\Installer\NetworkedDatabaseCreator\existsInLoadBalancer().

◆ getConnectionInternal()

Wikimedia\Rdbms\ILoadBalancer::getConnectionInternal	(	$i,
		$groups = [],
		$domain = false,
		$flags = 0 )

Access: internal: Only to be used by DBConnRef

Parameters

int	$i	Specific (overrides $groups) or virtual (DB_PRIMARY/DB_REPLICA) server index
string[] \| string	$groups	Query group(s) in preference order; [] for the default group
string \| false	$domain	DB domain ID or false for the local domain
int	$flags	Bitfield of CONN_* class constants (e.g. CONN_TRX_AUTOCOMMIT)

Returns: IDatabase

Implemented in Wikimedia\Rdbms\LoadBalancer, and Wikimedia\Rdbms\LoadBalancerDisabled.

◆ getConnectionRef()

Wikimedia\Rdbms\ILoadBalancer::getConnectionRef	(	$i,
		$groups = [],
		$domain = false,
		$flags = 0 )

Deprecated: since 1.39, use ILoadBalancer::getConnection() instead.

Parameters

int	$i	Specific or virtual (DB_PRIMARY/DB_REPLICA) server index
string[] \| string	$groups	Query group(s) in preference order; [] for the default group
string \| false	$domain	DB domain ID or false for the local domain
int	$flags	Bitfield of CONN_* class constants (e.g. CONN_TRX_AUTOCOMMIT)

Returns: DBConnRef

Implemented in Wikimedia\Rdbms\LoadBalancer, and Wikimedia\Rdbms\LoadBalancerDisabled.

◆ getLagTimes()

Wikimedia\Rdbms\ILoadBalancer::getLagTimes ( )

Get an estimate of replication lag (in seconds) for each server.

Results are cached for a short time in memcached/process cache

Values may be "false" if replication is too broken to estimate

Returns: float[]|int[]|false[] Map of (server index => lag) in order of server index

Implemented in Wikimedia\Rdbms\LoadBalancer.

◆ getLocalDomainID()

Wikimedia\Rdbms\ILoadBalancer::getLocalDomainID ( )

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

See also: DatabaseDomain

Returns: string Database domain ID; this specifies DB name, schema, and table prefix

Since: 1.31

Implemented in Wikimedia\Rdbms\LoadBalancer.

◆ getMaintenanceConnectionRef()

Wikimedia\Rdbms\ILoadBalancer::getMaintenanceConnectionRef	(	$i,
		$groups = [],
		$domain = false,
		$flags = 0 )

Get a DB handle, suitable for migrations and schema changes, for a server index.

The DBConnRef methods simply proxy an underlying IDatabase object which takes care of the actual connection and query logic.

The CONN_TRX_AUTOCOMMIT flag is ignored for databases with ATTR_DB_LEVEL_LOCKING (e.g. sqlite) in order to avoid deadlocks. getServerAttributes() can be used to check such flags beforehand. Avoid the use of begin() or startAtomic() on any CONN_TRX_AUTOCOMMIT connections.

See also: ILoadBalancer::getConnection() for parameter information

Parameters

int	$i	Specific or virtual (DB_PRIMARY/DB_REPLICA) server index
string[] \| string	$groups	Query group(s) in preference order; [] for the default group
string \| false	$domain	DB domain ID or false for the local domain
int	$flags	Bitfield of CONN_* class constants (e.g. CONN_TRX_AUTOCOMMIT)

Returns: DBConnRef

Implemented in Wikimedia\Rdbms\LoadBalancer, and Wikimedia\Rdbms\LoadBalancerDisabled.

◆ getMaxLag()

Wikimedia\Rdbms\ILoadBalancer::getMaxLag ( )

Get the name and lag time of the most-lagged replica server.

This is useful for maintenance scripts that need to throttle their updates. May attempt to open connections to replica DBs on the default DB. If there is no lag, the maximum lag will be reported as -1.

Returns: array{0:string,1:float|int|false,2:int} (host, max lag, index of max lagged host)

Implemented in Wikimedia\Rdbms\LoadBalancer.

◆ getPrimaryPos()

Wikimedia\Rdbms\ILoadBalancer::getPrimaryPos ( )

Get the current primary replication position.

Returns: DBPrimaryPos|false Returns false if not applicable

Exceptions

DBError

Since: 1.37

Implemented in Wikimedia\Rdbms\LoadBalancer.

Referenced by Wikimedia\Rdbms\ChronologyProtector\stageSessionPrimaryPos().

◆ getReaderIndex()

Wikimedia\Rdbms\ILoadBalancer::getReaderIndex ( $group = false )

Get the specific server index of the reader connection for a given group.

This takes into account load ratios and lag times. It should return a consistent index during the life time of the load balancer. This initially checks replica DBs for connectivity to avoid returning an unusable server. This means that connections might be attempted by calling this method (usually one at the most but possibly more). Subsequent calls with the same $group will not need to make new connection attempts since the acquired connection for each group is preserved.

Parameters

string | false $group Query group or false for the generic group

Returns: int|false Specific server index, or false if no DB handle can be obtained

Implemented in Wikimedia\Rdbms\LoadBalancer.

◆ getReadOnlyReason()

Wikimedia\Rdbms\ILoadBalancer::getReadOnlyReason ( )

Note: This method may trigger a DB connection if not yet done

Returns: string|false Reason the primary is read-only or false if it is not

Implemented in Wikimedia\Rdbms\LoadBalancer.

◆ getServerAttributes()

Wikimedia\Rdbms\ILoadBalancer::getServerAttributes ( $i )

Get basic attributes of the server with the specified index without connecting.

Parameters

int $i Specific server index

Returns: array (Database::ATTRIBUTE_* constant => value) for all such constants

Since: 1.31

Implemented in Wikimedia\Rdbms\LoadBalancer.

◆ getServerConnection()

Wikimedia\Rdbms\ILoadBalancer::getServerConnection	(	$i,
		$domain,
		$flags = 0 )

Get a DB handle for a specific server index.

This is an internal utility method for methods like LoadBalancer::getConnectionInternal() and DBConnRef to create the underlying connection to a concrete server.

The following is the responsibility of the caller:

translate any virtual server indexes (DB_PRIMARY/DB_REPLICA) to a real server index.
enforce read-only mode on primary DB handle if there is high replication lag.

See also: ILoadBalancer::getConnection()

Access: internal: Only for use within ILoadBalancer/ILoadMonitor

Parameters

int	$i	Specific server index
string	$domain	Resolved DB domain
int	$flags	Bitfield of class CONN_* constants

Returns: IDatabaseForOwner|false This returns false on failure if CONN_SILENCE_ERRORS is set

Exceptions

DBError If no DB handle could be obtained and CONN_SILENCE_ERRORS is not set

Implemented in Wikimedia\Rdbms\LoadBalancer.

◆ getServerCount()

Wikimedia\Rdbms\ILoadBalancer::getServerCount ( )

Get the number of servers defined in configuration.

Returns: int

Implemented in Wikimedia\Rdbms\LoadBalancer.

◆ getServerInfo()

Wikimedia\Rdbms\ILoadBalancer::getServerInfo ( $i )

Return the server configuration map for the server with the specified index.

Parameters

int $i Specific server index

Returns: array|false Server configuration map; false if the index is invalid

Since: 1.31

Implemented in Wikimedia\Rdbms\LoadBalancer.

◆ getServerName()

Wikimedia\Rdbms\ILoadBalancer::getServerName ( $i )

Get the readable name of the server with the specified index.

Parameters

int $i Specific server index

Returns: string Readable server name, falling back to the hostname or IP address

Implemented in Wikimedia\Rdbms\LoadBalancer.

Referenced by Wikimedia\Rdbms\ChronologyProtector\getSessionPrimaryPos(), and Wikimedia\Rdbms\ChronologyProtector\stageSessionPrimaryPos().

◆ getServerType()

Wikimedia\Rdbms\ILoadBalancer::getServerType ( $i )

Get the RDBMS type of the server with the specified index (e.g.

"mysql", "sqlite")

Parameters

int $i Specific server index

Returns: string One of (mysql,postgres,sqlite,...) or "unknown" for bad indexes

Since: 1.30

Implemented in Wikimedia\Rdbms\LoadBalancer.

◆ hasOrMadeRecentPrimaryChanges()

Wikimedia\Rdbms\ILoadBalancer::hasOrMadeRecentPrimaryChanges ( $age = null )

Check if this load balancer object had any recent or still pending writes issued against it by this PHP thread.

Parameters

float | null $age How many seconds ago is "recent" [defaults to mWaitTimeout]

Returns: bool

Since: 1.37

Implemented in Wikimedia\Rdbms\LoadBalancer.

Referenced by Wikimedia\Rdbms\ChronologyProtector\stageSessionPrimaryPos().

◆ hasPrimaryChanges()

Wikimedia\Rdbms\ILoadBalancer::hasPrimaryChanges ( )

Whether there are pending changes or callbacks in a transaction by this thread.

Returns: bool

Since: 1.37

Implemented in Wikimedia\Rdbms\LoadBalancer.

◆ hasReplicaServers()

Wikimedia\Rdbms\ILoadBalancer::hasReplicaServers ( )

Whether there are any replica servers configured.

This scans the list of servers defined in configuration, checking for:

Servers that are listed after the primary and not flagged with "is static"; such servers are assumed to be typical streaming replicas
Servers that are listed after the primary and flagged with "is static"; such servers are assumed to have a clone of the static dataset (matching the primary)

Returns: bool

Since: 1.34

Implemented in Wikimedia\Rdbms\LoadBalancer.

◆ hasStreamingReplicaServers()

Wikimedia\Rdbms\ILoadBalancer::hasStreamingReplicaServers ( )

Whether any replica servers use streaming replication from the primary server.

This scans the list of servers defined in configuration, checking for:

Servers that are listed after the primary and not flagged with "is static"; such servers are assumed to be typical streaming replicas

It is possible for some replicas to be configured with "is static" but not others, though it generally should either be set for all or none of the replicas.

If this returns false, this means that there is generally no reason to execute replication wait logic for session consistency and lag reduction.

Returns: bool

Since: 1.34

Implemented in Wikimedia\Rdbms\LoadBalancer.

Referenced by Wikimedia\Rdbms\ChronologyProtector\stageSessionPrimaryPos().

◆ pingAll()

Wikimedia\Rdbms\ILoadBalancer::pingAll ( )

Returns: bool

Implemented in Wikimedia\Rdbms\LoadBalancer.

◆ resolveDomainID()

Wikimedia\Rdbms\ILoadBalancer::resolveDomainID ( $domain )

Parameters

DatabaseDomain | string | false $domain Database domain

Returns: string Value of $domain if it is foreign or the local domain otherwise

Since: 1.32

Implemented in Wikimedia\Rdbms\LoadBalancer.

◆ setDomainAliases()

Wikimedia\Rdbms\ILoadBalancer::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

Implemented in Wikimedia\Rdbms\LoadBalancer.

Referenced by Wikimedia\Rdbms\LBFactory\initLoadBalancer().

◆ setTableAliases()

Wikimedia\Rdbms\ILoadBalancer::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)

Implemented in Wikimedia\Rdbms\LoadBalancer.

Referenced by Wikimedia\Rdbms\LBFactory\initLoadBalancer().

◆ setTempTablesOnlyMode()

Wikimedia\Rdbms\ILoadBalancer::setTempTablesOnlyMode	(		$value,
			$domain )

Indicate whether the tables on this domain are only temporary tables for testing.

In "temporary tables mode", the CONN_TRX_AUTOCOMMIT flag is ignored

Parameters

bool	$value
string	$domain

Returns: bool Whether "temporary tables mode" was active

Since: 1.34

Implemented in Wikimedia\Rdbms\LoadBalancer.

◆ setTransactionListener()

Wikimedia\Rdbms\ILoadBalancer::setTransactionListener	(		$name,
		?callable	$callback = null )

Set a callback via IDatabase::setTransactionListener() on all current and future primary connections of this load balancer.

Parameters

string	$name	Callback name
callable \| null	$callback

Implemented in Wikimedia\Rdbms\LoadBalancer.

◆ waitForPrimaryPos()

Wikimedia\Rdbms\ILoadBalancer::waitForPrimaryPos ( IDatabase $conn )

Wait for a replica DB to reach a specified primary position.

If $conn is not a replica server connection, then this will return true. Otherwise, if $pos is not provided, this will connect to the primary server to get an accurate position.

Parameters

IDatabase $conn Replica DB

Returns: bool Success

Since: 1.37

Implemented in Wikimedia\Rdbms\LoadBalancer.

Member Data Documentation

◆ CONN_SILENCE_ERRORS

const Wikimedia\Rdbms\ILoadBalancer::CONN_SILENCE_ERRORS = 4

Yield null on connection failure instead of throwing an exception.

Access: internal

Definition at line 141 of file ILoadBalancer.php.

Referenced by Wikimedia\Rdbms\LoadMonitor\computeServerState().

◆ CONN_TRX_AUTOCOMMIT

const Wikimedia\Rdbms\ILoadBalancer::CONN_TRX_AUTOCOMMIT = 1

Yield a tracked autocommit-mode handle (reuse existing ones)

Definition at line 131 of file ILoadBalancer.php.

Referenced by Wikimedia\Rdbms\LoadBalancerSingle\sanitizeConnectionFlags().

◆ CONN_UNTRACKED_GAUGE

const Wikimedia\Rdbms\ILoadBalancer::CONN_UNTRACKED_GAUGE = 2

Yield an untracked, low-timeout, autocommit-mode handle (to gauge server health)

Access: internal

Definition at line 136 of file ILoadBalancer.php.

Referenced by Wikimedia\Rdbms\LoadMonitor\computeServerState().

◆ DB_PRIMARY

const Wikimedia\Rdbms\ILoadBalancer::DB_PRIMARY = -2

Request a primary, write-enabled DB connection.

Can't be used as a binary flag with bitwise operators!

Since: 1.36

Definition at line 123 of file ILoadBalancer.php.

Referenced by Wikimedia\Rdbms\DBConnRef\query().

◆ DB_REPLICA

const Wikimedia\Rdbms\ILoadBalancer::DB_REPLICA = -1

Request a replica DB connection.

Can't be used as a binary flag with bitwise operators!

Definition at line 117 of file ILoadBalancer.php.

◆ DOMAIN_ANY

const Wikimedia\Rdbms\ILoadBalancer::DOMAIN_ANY = ''

Domain specifier when no specific database needs to be selected.

Definition at line 126 of file ILoadBalancer.php.

Referenced by Wikimedia\Rdbms\LoadMonitor\computeServerState().

◆ GROUP_GENERIC

const Wikimedia\Rdbms\ILoadBalancer::GROUP_GENERIC = ''

The generic query group.

Definition at line 128 of file ILoadBalancer.php.

Referenced by Wikimedia\Rdbms\LBFactoryMulti\__construct().

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

includes/libs/rdbms/loadbalancer/ILoadBalancer.php

Public Member Functions

Public Attributes

Detailed Description

Member Function Documentation

◆ explicitTrxActive()

◆ getClusterName()

◆ getConnection()

◆ getConnectionInternal()

◆ getConnectionRef()

◆ getLagTimes()

◆ getLocalDomainID()

◆ getMaintenanceConnectionRef()

◆ getMaxLag()

◆ getPrimaryPos()

◆ getReaderIndex()

◆ getReadOnlyReason()

◆ getServerAttributes()

◆ getServerConnection()

◆ getServerCount()

◆ getServerInfo()

◆ getServerName()

◆ getServerType()

◆ hasOrMadeRecentPrimaryChanges()

◆ hasPrimaryChanges()

◆ hasReplicaServers()

◆ hasStreamingReplicaServers()

◆ pingAll()

◆ resolveDomainID()

◆ setDomainAliases()

◆ setTableAliases()

◆ setTempTablesOnlyMode()

◆ setTransactionListener()

◆ waitForPrimaryPos()

Member Data Documentation

◆ CONN_SILENCE_ERRORS

◆ CONN_TRX_AUTOCOMMIT

◆ CONN_UNTRACKED_GAUGE

◆ DB_PRIMARY

◆ DB_REPLICA

◆ DOMAIN_ANY

◆ GROUP_GENERIC