com.netflix.fenzo.plugins

Class UniqueHostAttrConstraint

java.lang.Object

com.netflix.fenzo.plugins.UniqueHostAttrConstraint

All Implemented Interfaces:

ConstraintEvaluator

public class UniqueHostAttrConstraint
extends java.lang.Object
implements ConstraintEvaluator

A unique constraint evaluator that constrains tasks according to a given host attribute. Use this evaluator to constrain a given set of tasks (co-tasks) by assigning them to hosts such that each task is assigned to a host that has a different value for the host attribute you specify.

For example, if you specify the host attribute ZoneAttribute, the evaluator will place the co-tasks such that each task is in a different zone. Note that because of this, if more tasks are submitted than there are zones available for them, the excess tasks will not be assigned to any hosts. If instead you want to implement a load balancing strategy, use BalancedHostAttrConstraint instead.

If you construct this evaluator without passing in a host attribute name, it will use the host name as the host attribute by which it uniquely identifies hosts.

Nested Class Summary

Nested classes/interfaces inherited from interface com.netflix.fenzo.ConstraintEvaluator

ConstraintEvaluator.Result

Constructor Summary

Constructors

Constructor and Description
UniqueHostAttrConstraint(Func1<java.lang.String,java.util.Set<java.lang.String>> coTasksGetter) Create this constraint evaluator with the given co-tasks of a group.
UniqueHostAttrConstraint(Func1<java.lang.String,java.util.Set<java.lang.String>> coTasksGetter, java.lang.String hostAttributeName) Create this constraint evaluator with the given co-tasks of a group and a given host attribute name.

Method Summary

Modifier and Type	Method and Description
ConstraintEvaluator.Result	evaluate(TaskRequest taskRequest, VirtualMachineCurrentState targetVM, TaskTrackerState taskTrackerState) Determines whether a particular target host is appropriate for a particular task request by rejecting any host that has the same value for the unique constraint attribute as another host that is already assigned a co-task of the specified task request.
java.lang.String	getName() Returns the name of this constraint evaluator as a String in the form of the name of this class followed by a dash followed by the host attribute name that this evaluator uses to uniquely identify the host.

Methods inherited from class java.lang.Object

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

Constructor Detail

UniqueHostAttrConstraint

public UniqueHostAttrConstraint(Func1<java.lang.String,java.util.Set<java.lang.String>> coTasksGetter)

Create this constraint evaluator with the given co-tasks of a group. This is equivalent to UniqueHostAttrConstraint(coTasksGetter, null).

Parameters:

coTasksGetter - a single-argument function that, given a task ID, returns the set of task IDs of its co-tasks

UniqueHostAttrConstraint

public UniqueHostAttrConstraint(Func1<java.lang.String,java.util.Set<java.lang.String>> coTasksGetter,
                                java.lang.String hostAttributeName)

Create this constraint evaluator with the given co-tasks of a group and a given host attribute name.

Parameters:

coTasksGetter - a single-argument function that, given a task ID, returns the set of task IDs of its co-tasks

hostAttributeName - the name of the host attribute whose value is to be unique for each co-task's host assignment. If this is null, this indicates that the host name is to be unique for each co-task's host assignment.

Method Detail

getName

public java.lang.String getName()

Returns the name of this constraint evaluator as a String in the form of the name of this class followed by a dash followed by the host attribute name that this evaluator uses to uniquely identify the host.

Specified by:

getName in interface ConstraintEvaluator

Returns:

the name of this constraint evaluator

evaluate

public ConstraintEvaluator.Result evaluate(TaskRequest taskRequest,
                                           VirtualMachineCurrentState targetVM,
                                           TaskTrackerState taskTrackerState)

Determines whether a particular target host is appropriate for a particular task request by rejecting any host that has the same value for the unique constraint attribute as another host that is already assigned a co-task of the specified task request.

Specified by:

evaluate in interface ConstraintEvaluator

Parameters:

taskRequest - describes the task being considered for assignment to the host

targetVM - describes the host being considered as a target for the task

taskTrackerState - describes the state of tasks previously assigned or already running throughout the system

Returns:

a successful Result if the target does not have the same value for its unique constraint attribute as another host that has already been assigned a co-task of taskRequest, or an unsuccessful Result otherwise