com.datastax.driver.core.policies

Class ConstantSpeculativeExecutionPolicy

java.lang.Object

com.datastax.driver.core.policies.ConstantSpeculativeExecutionPolicy

All Implemented Interfaces:

SpeculativeExecutionPolicy

public class ConstantSpeculativeExecutionPolicy
extends Object
implements SpeculativeExecutionPolicy

A SpeculativeExecutionPolicy that schedules a given number of speculative executions, separated by a fixed delay.

Nested Class Summary

Nested classes/interfaces inherited from interface com.datastax.driver.core.policies.SpeculativeExecutionPolicy

SpeculativeExecutionPolicy.SpeculativeExecutionPlan

Constructor Summary

Constructors

Constructor and Description
ConstantSpeculativeExecutionPolicy(long constantDelayMillis, int maxSpeculativeExecutions) Builds a new instance.

Method Summary

Modifier and Type	Method and Description
void	close() Gets invoked at cluster shutdown.
long	getConstantDelayMillis()
int	getMaxSpeculativeExecutions()
void	init(Cluster cluster) Gets invoked at cluster startup.
SpeculativeExecutionPolicy.SpeculativeExecutionPlan	newPlan(String loggedKeyspace, Statement statement) Returns the plan to use for a new query.

Methods inherited from class java.lang.Object

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

Constructor Detail

ConstantSpeculativeExecutionPolicy

public ConstantSpeculativeExecutionPolicy(long constantDelayMillis,
                                          int maxSpeculativeExecutions)

Builds a new instance.

Parameters:

constantDelayMillis - the delay between each speculative execution. Must be >= 0. A zero delay means it should immediately send `maxSpeculativeExecutions` requests along with the original request.

maxSpeculativeExecutions - the number of speculative executions. Must be strictly positive.

Throws:

IllegalArgumentException - if one of the arguments does not respect the preconditions above.

Method Detail

newPlan

public SpeculativeExecutionPolicy.SpeculativeExecutionPlan newPlan(String loggedKeyspace,
                                                                   Statement statement)

Description copied from interface: SpeculativeExecutionPolicy

Returns the plan to use for a new query.

Specified by:

newPlan in interface SpeculativeExecutionPolicy

Parameters:

loggedKeyspace - the currently logged keyspace (the one set through either Cluster.connect(String) or by manually doing a USE query) for the session on which this plan need to be built. This can be null if the corresponding session has no keyspace logged in.

statement - the query for which to build a plan.

Returns:

the plan.

init

public void init(Cluster cluster)

Description copied from interface: SpeculativeExecutionPolicy

Gets invoked at cluster startup.

Specified by:

init in interface SpeculativeExecutionPolicy

Parameters:

cluster - the cluster that this policy is associated with.

close

public void close()

Description copied from interface: SpeculativeExecutionPolicy

Gets invoked at cluster shutdown.

This gives the policy the opportunity to perform some cleanup, for instance stop threads that it might have started.

Specified by:

close in interface SpeculativeExecutionPolicy

getMaxSpeculativeExecutions

public int getMaxSpeculativeExecutions()

getConstantDelayMillis

public long getConstantDelayMillis()