software.amazon.jdbc

Class LowestLoadHostSelector

java.lang.Object

software.amazon.jdbc.LowestLoadHostSelector

All Implemented Interfaces:

HostSelector

public class LowestLoadHostSelector
extends java.lang.Object
implements HostSelector

Host selector that picks the lowest-loaded reader using a calculated load derived from HostSpec.getCpuPercent() and HostSpec.getLagMs()

Note: Non-Aurora dialects may not be compatible as they do not populate host cpuPercent or lagMs.

Field Summary

Fields

Modifier and Type	Field and Description
protected static long	CPU_DEFAULT
protected static long	LAG_MS_DEFAULT
static AwsWrapperProperty	LOWEST_LOAD_CPU_WEIGHT
static AwsWrapperProperty	LOWEST_LOAD_LAG_WEIGHT
static java.lang.String	STRATEGY_LOWEST_LOAD
static java.lang.String	STRATEGY_LOWEST_LOAD_BY_CPU
static java.lang.String	STRATEGY_LOWEST_LOAD_BY_LAG

Constructor Summary

Constructors

Constructor and Description
LowestLoadHostSelector()
LowestLoadHostSelector(long defaultCpuWeight, long defaultLagWeight)

Method Summary

Modifier and Type	Method and Description
static LowestLoadHostSelector	byCpu()
static LowestLoadHostSelector	byLag()
@Nullable HostSpec	getHost(@NonNull java.util.List<HostSpec> hosts, @Nullable HostRole role, @Nullable java.util.Properties props) Selects a host with the requested role from the given host list.

Methods inherited from class java.lang.Object

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

Field Detail

STRATEGY_LOWEST_LOAD

public static final java.lang.String STRATEGY_LOWEST_LOAD

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Constant Field Values

STRATEGY_LOWEST_LOAD_BY_CPU

public static final java.lang.String STRATEGY_LOWEST_LOAD_BY_CPU

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Constant Field Values

STRATEGY_LOWEST_LOAD_BY_LAG

public static final java.lang.String STRATEGY_LOWEST_LOAD_BY_LAG

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Constant Field Values

LOWEST_LOAD_CPU_WEIGHT

public static final AwsWrapperProperty LOWEST_LOAD_CPU_WEIGHT

LOWEST_LOAD_LAG_WEIGHT

public static final AwsWrapperProperty LOWEST_LOAD_LAG_WEIGHT

CPU_DEFAULT

protected static final long CPU_DEFAULT

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Constant Field Values

LAG_MS_DEFAULT

protected static final long LAG_MS_DEFAULT

See Also:

Constant Field Values

Constructor Detail

LowestLoadHostSelector

public LowestLoadHostSelector()

LowestLoadHostSelector

public LowestLoadHostSelector(long defaultCpuWeight,
                              long defaultLagWeight)

Method Detail

byCpu

public static LowestLoadHostSelector byCpu()

byLag

public static LowestLoadHostSelector byLag()

getHost

public @Nullable HostSpec getHost(@NonNull java.util.List<HostSpec> hosts,
                                  @Nullable HostRole role,
                                  @Nullable java.util.Properties props)
                           throws java.sql.SQLException

Description copied from interface: HostSelector

Selects a host with the requested role from the given host list.

Specified by:

getHost in interface HostSelector

Parameters:

hosts - a list of available hosts to pick from.

role - the desired host role - either a writer or a reader. Null value means no preferences on host role.

props - connection properties that may be needed by the host selector in order to choose a host.

Returns:

a host matching the requested role, or null if no hosts match the requested role

Throws:

java.sql.SQLException - if an error occurs while selecting a host