org.apache.flink.runtime.instance

Class SlotSharingGroupAssignment

java.lang.Object

org.apache.flink.runtime.instance.SlotSharingGroupAssignment

public class SlotSharingGroupAssignment
extends Object

The SlotSharingGroupAssignment manages a set of shared slots, which are shared between tasks of a SlotSharingGroup.

The assignments shares tasks by allowing a shared slot to hold one vertex per JobVertexID. For example, consider a program consisting of job vertices "source", "map", "reduce", and "sink". If the slot sharing group spans all four job vertices, then each shared slot can hold one parallel subtask of the source, the map, the reduce, and the sink vertex. Each shared slot holds the actual subtasks in child slots, which are (at the leaf level), the SimpleSlots.

An exception are the co-location-constraints, that define that the i-th subtask of one vertex needs to be scheduled strictly together with the i-th subtasks of the vertices that share the co-location-constraint. To manage that, a co-location-constraint gets its own shared slot inside the shared slots of a sharing group.

Consider a job set up like this:

 +-------------- Slot Sharing Group --------------+
 |                                                |
 |            +-- Co Location Group --+           |
 |            |                       |           |
 |  (source) ---> (head) ---> (tail) ---> (sink)  |
 |            |                       |           |
 |            +-----------------------+           |
 +------------------------------------------------+
 

The slot hierarchy in the slot sharing group will look like the following

     Shared(0)(root)
        |
        +-- Simple(2)(sink)
        |
        +-- Shared(1)(co-location-group)
        |      |
        |      +-- Simple(0)(tail)
        |      +-- Simple(1)(head)
        |
        +-- Simple(0)(source)
 

Constructor Summary

Constructors

Constructor and Description
SlotSharingGroupAssignment()

Method Summary

Modifier and Type	Method and Description
SimpleSlot	addSharedSlotAndAllocateSubSlot(SharedSlot sharedSlot, Locality locality, CoLocationConstraint constraint)
SimpleSlot	addSharedSlotAndAllocateSubSlot(SharedSlot sharedSlot, Locality locality, JobVertexID groupId)
int	getNumberOfAvailableSlotsForGroup(AbstractID groupId) Gets the number of shared slots into which the given group can place subtasks or nested task groups.
int	getNumberOfSlots() Gets the number of slots that are currently governed by this assignment group.
Tuple2<SharedSlot,Locality>	getSharedSlotForTask(AbstractID groupId, Iterable<TaskManagerLocation> preferredLocations, boolean localOnly)
SimpleSlot	getSlotForTask(CoLocationConstraint constraint, Iterable<TaskManagerLocation> locationPreferences) Gets a slot for a task that has a co-location constraint.
SimpleSlot	getSlotForTask(JobVertexID vertexID, Iterable<TaskManagerLocation> locationPreferences) Gets a slot suitable for the given task vertex.

Methods inherited from class java.lang.Object

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

Constructor Detail

SlotSharingGroupAssignment

public SlotSharingGroupAssignment()

Method Detail

getNumberOfSlots

public int getNumberOfSlots()

Gets the number of slots that are currently governed by this assignment group. This refers to the slots allocated from an Instance, and not the sub-slots given out as children of those shared slots.

Returns:

The number of resource slots managed by this assignment group.

getNumberOfAvailableSlotsForGroup

public int getNumberOfAvailableSlotsForGroup(AbstractID groupId)

Gets the number of shared slots into which the given group can place subtasks or nested task groups.

Parameters:

groupId - The ID of the group.

Returns:

The number of shared slots available to the given job vertex.

addSharedSlotAndAllocateSubSlot

public SimpleSlot addSharedSlotAndAllocateSubSlot(SharedSlot sharedSlot,
                                                  Locality locality,
                                                  JobVertexID groupId)

addSharedSlotAndAllocateSubSlot

public SimpleSlot addSharedSlotAndAllocateSubSlot(SharedSlot sharedSlot,
                                                  Locality locality,
                                                  CoLocationConstraint constraint)

getSlotForTask

public SimpleSlot getSlotForTask(JobVertexID vertexID,
                                 Iterable<TaskManagerLocation> locationPreferences)

Gets a slot suitable for the given task vertex. This method will prefer slots that are local (with respect to ExecutionVertex.getPreferredLocationsBasedOnInputs()), but will return non local slots if no local slot is available. The method returns null, when this sharing group has no slot is available for the given JobVertexID.

Parameters:

vertexID - the vertex id

locationPreferences - location preferences

Returns:

A slot to execute the given ExecutionVertex in, or null, if none is available.

getSlotForTask

public SimpleSlot getSlotForTask(CoLocationConstraint constraint,
                                 Iterable<TaskManagerLocation> locationPreferences)

Gets a slot for a task that has a co-location constraint. This method tries to grab a slot form the location-constraint's shared slot. If that slot has not been initialized, then the method tries to grab another slot that is available for the location-constraint-group.

In cases where the co-location constraint has not yet been initialized with a slot, or where that slot has been disposed in the meantime, this method tries to allocate a shared slot for the co-location constraint (inside on of the other available slots).

If a suitable shared slot is available, this method allocates a simple slot within that shared slot and returns it. If no suitable shared slot could be found, this method returns null.

Parameters:

constraint - The co-location constraint for the placement of the execution vertex.

locationPreferences - location preferences

Returns:

A simple slot allocate within a suitable shared slot, or null, if no suitable shared slot is available.

getSharedSlotForTask

public Tuple2<SharedSlot,Locality> getSharedSlotForTask(AbstractID groupId,
                                                        Iterable<TaskManagerLocation> preferredLocations,
                                                        boolean localOnly)