com.mysql.cj.jdbc.ha

Class LoadBalancedConnectionProxy

java.lang.Object

com.mysql.cj.jdbc.ha.MultiHostConnectionProxy

com.mysql.cj.jdbc.ha.LoadBalancedConnectionProxy

All Implemented Interfaces:

PingTarget, java.lang.reflect.InvocationHandler

public class LoadBalancedConnectionProxy
extends MultiHostConnectionProxy
implements PingTarget

A proxy for a dynamic com.mysql.cj.jdbc.JdbcConnection implementation that load balances requests across a series of MySQL JDBC connections, where the balancing takes place at transaction commit. Therefore, for this to work (at all), you must use transactions, even if only reading data. This implementation will invalidate connections that it detects have had communication errors when processing a request. Problematic hosts will be added to a global blacklist for loadBalanceBlacklistTimeout ms, after which they will be removed from the blacklist and made eligible once again to be selected for new connections. This implementation is thread-safe, but it's questionable whether sharing a connection instance amongst threads is a good idea, given that transactions are scoped to connections in JDBC.

Field Summary

Fields

Modifier and Type	Field and Description
protected java.util.Map<java.lang.String,ConnectionImpl>	liveConnections

Fields inherited from class com.mysql.cj.jdbc.ha.MultiHostConnectionProxy

autoReconnect, closedExplicitly, closedReason, connectionUrl, currentConnection, hostsList, isClosed, lastExceptionDealtWith, thisAsConnection

Constructor Summary

Constructors

Constructor and Description
LoadBalancedConnectionProxy(ConnectionUrl connectionUrl) Creates a proxy for java.sql.Connection that routes requests between the hosts in the connection URL.

Method Summary

Modifier and Type	Method and Description
boolean	addHost(java.lang.String hostPortPair) Adds a host to the hosts list.
void	addToGlobalBlacklist(java.lang.String host) Adds a host to the blacklist.
void	addToGlobalBlacklist(java.lang.String host, long timeout) Adds a host to the blacklist with the given timeout.
ConnectionImpl	createConnectionForHost(HostInfo hostInfo) Creates a new physical connection for the given HostInfo and updates required internal mappings and statistics for that connection.
ConnectionImpl	createConnectionForHost(java.lang.String hostPortPair) Creates a new physical connection for the given host:port info.
static LoadBalancedConnection	createProxyInstance(ConnectionUrl connectionUrl) Static factory to create LoadBalancedConnection instances.
protected void	doAbort(java.util.concurrent.Executor executor) Aborts all live connections, using the provided Executor.
protected void	doAbortInternal() Aborts all live connections
protected void	doClose() Closes all live connections.
void	doPing() Pings live connections.
long	getActivePhysicalConnectionCount()
long	getConnectionGroupProxyID()
java.lang.String	getCurrentActiveHost()
long	getCurrentTransactionDuration()
java.util.Map<java.lang.String,java.lang.Long>	getGlobalBlacklist() Returns a local hosts blacklist, while cleaning up expired records from the global blacklist, or a blacklist with the hosts to be removed.
long	getTotalPhysicalConnectionCount()
long	getTransactionCount()
boolean	inTransaction()
protected void	invalidateConnection(JdbcConnection conn) Closes specified connection and removes it from required mappings.
java.lang.Object	invokeMore(java.lang.Object proxy, java.lang.reflect.Method method, java.lang.Object[] args) Proxies method invocation on the java.sql.Connection interface, trapping "close", "isClosed" and "commit/rollback" to switch connections for load balancing.
boolean	isGlobalBlacklistEnabled() Checks if host blacklist management was enabled.
protected boolean	isMasterConnection() Always returns 'true' as there are no "masters" and "slaves" in this type of connection.
void	pickNewConnection() Picks the "best" connection to use for the next transaction based on the BalanceStrategy in use.
protected void	propagateProxyDown(JdbcConnection proxyConn) Propagates the connection proxy down through all live connections.
void	removeHost(java.lang.String hostPortPair) Removes a host from the host list.
void	removeHostWhenNotInUse(java.lang.String hostPortPair) Removes a host from the host list, allowing it some time to be released gracefully if needed.
protected boolean	shouldExceptionTriggerConnectionSwitch(java.lang.Throwable t) Consults the registered LoadBalanceExceptionChecker if the given exception should trigger a connection fail-over.
boolean	shouldExceptionTriggerFailover(java.lang.Throwable t) Deprecated.
protected void	syncSessionState(JdbcConnection source, JdbcConnection target, boolean readOnly) Synchronizes session state between two connections, allowing to override the read-only status.

Methods inherited from class com.mysql.cj.jdbc.ha.MultiHostConnectionProxy

allowedOnClosedConnection, dealWithInvocationException, getNewJdbcInterfaceProxy, getParentProxy, getProxy, invalidateCurrentConnection, invoke, proxyIfReturnTypeIsJdbcInterface, setProxy

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

liveConnections

protected java.util.Map<java.lang.String,ConnectionImpl> liveConnections

Constructor Detail

LoadBalancedConnectionProxy

public LoadBalancedConnectionProxy(ConnectionUrl connectionUrl)
                            throws java.sql.SQLException

Creates a proxy for java.sql.Connection that routes requests between the hosts in the connection URL.

Parameters:

connectionUrl - The connection URL containing the hosts to load balance.

Throws:

java.sql.SQLException - if an error occurs

Method Detail

createProxyInstance

public static LoadBalancedConnection createProxyInstance(ConnectionUrl connectionUrl)
                                                  throws java.sql.SQLException

Static factory to create LoadBalancedConnection instances.

Parameters:

connectionUrl - The connection URL containing the hosts in a load-balance setup.

Returns:

A LoadBalancedConnection proxy.

Throws:

java.sql.SQLException - if an error occurs

propagateProxyDown

protected void propagateProxyDown(JdbcConnection proxyConn)

Propagates the connection proxy down through all live connections.

Overrides:

propagateProxyDown in class MultiHostConnectionProxy

Parameters:

proxyConn - The top level connection in the multi-host connections chain.

shouldExceptionTriggerFailover

@Deprecated
public boolean shouldExceptionTriggerFailover(java.lang.Throwable t)

Deprecated.

shouldExceptionTriggerConnectionSwitch

protected boolean shouldExceptionTriggerConnectionSwitch(java.lang.Throwable t)

Consults the registered LoadBalanceExceptionChecker if the given exception should trigger a connection fail-over.

Specified by:

shouldExceptionTriggerConnectionSwitch in class MultiHostConnectionProxy

Parameters:

t - The Exception instance to check.

Returns:

true if the given exception should trigger a connection fail-over

isMasterConnection

protected boolean isMasterConnection()

Always returns 'true' as there are no "masters" and "slaves" in this type of connection.

Specified by:

isMasterConnection in class MultiHostConnectionProxy

Returns:

true if current connection is to a master host

invalidateConnection

protected void invalidateConnection(JdbcConnection conn)
                             throws java.sql.SQLException

Closes specified connection and removes it from required mappings.

Overrides:

invalidateConnection in class MultiHostConnectionProxy

Parameters:

conn - connection

Throws:

java.sql.SQLException - if an error occurs

pickNewConnection

public void pickNewConnection()
                       throws java.sql.SQLException

Picks the "best" connection to use for the next transaction based on the BalanceStrategy in use.

Specified by:

pickNewConnection in class MultiHostConnectionProxy

Throws:

java.sql.SQLException - if an error occurs

createConnectionForHost

public ConnectionImpl createConnectionForHost(HostInfo hostInfo)
                                       throws java.sql.SQLException

Creates a new physical connection for the given HostInfo and updates required internal mappings and statistics for that connection.

Overrides:

createConnectionForHost in class MultiHostConnectionProxy

Parameters:

hostInfo - The host info instance.

Returns:

The new Connection instance.

Throws:

java.sql.SQLException - if an error occurs

syncSessionState

protected void syncSessionState(JdbcConnection source,
                                JdbcConnection target,
                                boolean readOnly)
                         throws java.sql.SQLException

Description copied from class: MultiHostConnectionProxy

Synchronizes session state between two connections, allowing to override the read-only status.

Overrides:

syncSessionState in class MultiHostConnectionProxy

Parameters:

source - The connection where to get state from.

target - The connection where to set state.

readOnly - The new read-only status.

Throws:

java.sql.SQLException - if an error occurs

createConnectionForHost

public ConnectionImpl createConnectionForHost(java.lang.String hostPortPair)
                                       throws java.sql.SQLException

Creates a new physical connection for the given host:port info. If the this connection's connection URL knows about this host:port then its host info is used, otherwise a new host info based on current connection URL defaults is spawned.

Parameters:

hostPortPair - The host:port pair identifying the host to connect to.

Returns:

The new Connection instance.

Throws:

java.sql.SQLException - if an error occurs

doClose

protected void doClose()

Closes all live connections.

Specified by:

doClose in class MultiHostConnectionProxy

doAbortInternal

protected void doAbortInternal()

Aborts all live connections

Specified by:

doAbortInternal in class MultiHostConnectionProxy

doAbort

protected void doAbort(java.util.concurrent.Executor executor)

Aborts all live connections, using the provided Executor.

Specified by:

doAbort in class MultiHostConnectionProxy

Parameters:

executor - executor

invokeMore

public java.lang.Object invokeMore(java.lang.Object proxy,
                                   java.lang.reflect.Method method,
                                   java.lang.Object[] args)
                            throws java.lang.Throwable

Proxies method invocation on the java.sql.Connection interface, trapping "close", "isClosed" and "commit/rollback" to switch connections for load balancing. This is the continuation of MultiHostConnectionProxy#invoke(Object, Method, Object[]).

Specified by:

invokeMore in class MultiHostConnectionProxy

Parameters:

proxy - proxy object

method - method to invoke

args - method parameters

Returns:

method result

Throws:

java.lang.Throwable - if an error occurs

doPing

public void doPing()
            throws java.sql.SQLException

Pings live connections.

Specified by:

doPing in interface PingTarget

Throws:

java.sql.SQLException - if an error occurs

addToGlobalBlacklist

public void addToGlobalBlacklist(java.lang.String host,
                                 long timeout)

Adds a host to the blacklist with the given timeout.

Parameters:

host - The host to be blacklisted.

timeout - The blacklist timeout for this entry.

addToGlobalBlacklist

public void addToGlobalBlacklist(java.lang.String host)

Adds a host to the blacklist.

Parameters:

host - The host to be blacklisted.

isGlobalBlacklistEnabled

public boolean isGlobalBlacklistEnabled()

Checks if host blacklist management was enabled.

Returns:

true if host blacklist management was enabled

getGlobalBlacklist

public java.util.Map<java.lang.String,java.lang.Long> getGlobalBlacklist()

Returns a local hosts blacklist, while cleaning up expired records from the global blacklist, or a blacklist with the hosts to be removed.

Returns:

A local hosts blacklist.

removeHostWhenNotInUse

public void removeHostWhenNotInUse(java.lang.String hostPortPair)
                            throws java.sql.SQLException

Removes a host from the host list, allowing it some time to be released gracefully if needed.

Parameters:

hostPortPair - The host to be removed.

Throws:

java.sql.SQLException - if an error occurs

removeHost

public void removeHost(java.lang.String hostPortPair)
                throws java.sql.SQLException

Removes a host from the host list.

Parameters:

hostPortPair - The host to be removed.

Throws:

java.sql.SQLException - if an error occurs

addHost

public boolean addHost(java.lang.String hostPortPair)

Adds a host to the hosts list.

Parameters:

hostPortPair - The host to be added.

Returns:

true if host was added and false if the host list already contains it

inTransaction

public boolean inTransaction()

getTransactionCount

public long getTransactionCount()

getActivePhysicalConnectionCount

public long getActivePhysicalConnectionCount()

getTotalPhysicalConnectionCount

public long getTotalPhysicalConnectionCount()

getConnectionGroupProxyID

public long getConnectionGroupProxyID()

getCurrentActiveHost

public java.lang.String getCurrentActiveHost()

getCurrentTransactionDuration

public long getCurrentTransactionDuration()