org.apache.flink.runtime.instance

Class Slot

java.lang.Object

org.apache.flink.runtime.instance.Slot

Direct Known Subclasses:

SharedSlot, SimpleSlot

public abstract class Slot
extends Object

Base class for slots that the Scheduler / ExecutionGraph take from the SlotPool and use to place tasks to execute into. A slot corresponds to an AllocatedSlot (a slice of a TaskManager's resources), plus additional fields to track what is currently executed in that slot, or if the slot is still used or disposed (ExecutionGraph gave it back to the pool).

In the simplest case, a slot holds a single task (SimpleSlot). In the more complex case, a slot is shared (SharedSlot) and contains a set of tasks. Shared slots may contain other shared slots which in turn can hold simple slots. That way, a shared slot may define a tree of slots that belong to it.

Field Summary

Fields

Modifier and Type	Field and Description
protected static AllocationID	NO_ALLOCATION_ID
protected static SlotRequestId	NO_SLOT_REQUEST_ID
protected static SlotSharingGroupId	NO_SLOT_SHARING_GROUP_ID

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Slot(SlotContext slotContext, SlotOwner owner, int slotNumber, SharedSlot parent, AbstractID groupID) Base constructor for slots.
protected	Slot(SlotOwner owner, TaskManagerLocation location, int slotNumber, TaskManagerGateway taskManagerGateway, SharedSlot parent, AbstractID groupID) Base constructor for slots.

Method Summary

Modifier and Type	Method and Description
boolean	equals(Object obj) Slots must always compare on referential equality.
AbstractID	getGroupID() Gets the ID that identifies the logical group to which this slot belongs: If the slot does not belong to any group in particular, this field is null. If this slot was allocated as a sub-slot of a SlotSharingGroupAssignment, then this ID will be the JobVertexID of the vertex whose task the slot holds in its shared slot. In case that the slot represents the shared slot of a co-location constraint, this ID will be the ID of the co-location constraint.
abstract int	getNumberLeaves() Gets the number of simple slots that are at the leaves of the tree of slots.
SlotOwner	getOwner() Gets the owner of this slot.
SharedSlot	getParent() Gets the parent slot of this slot.
Slot	getRoot() Gets the root slot of the tree containing this slot.
int	getRootSlotNumber() Gets the number of the root slot.
SlotContext	getSlotContext() Gets the allocated slot that this slot refers to.
int	getSlotNumber() Gets the number of the slot.
TaskManagerGateway	getTaskManagerGateway() Gets the actor gateway that can be used to send messages to the TaskManager.
ResourceID	getTaskManagerID() Gets the ID of the TaskManager that offers this slot.
TaskManagerLocation	getTaskManagerLocation() Gets the location info of the TaskManager that offers this slot.
int	hashCode() Slots must always has based on reference identity.
protected String	hierarchy()
boolean	isAlive() Checks of the slot is still alive, i.e.
boolean	isCanceled() Checks of the slot has been cancelled.
boolean	isReleased() Checks of the slot has been released.
abstract CompletableFuture<?>	releaseSlot(Throwable cause) This method cancels and releases the slot and all its sub-slots.
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

NO_ALLOCATION_ID

protected static final AllocationID NO_ALLOCATION_ID

NO_SLOT_REQUEST_ID

protected static final SlotRequestId NO_SLOT_REQUEST_ID

NO_SLOT_SHARING_GROUP_ID

protected static final SlotSharingGroupId NO_SLOT_SHARING_GROUP_ID

Constructor Detail

Slot

protected Slot(SlotOwner owner,
               TaskManagerLocation location,
               int slotNumber,
               TaskManagerGateway taskManagerGateway,
               @Nullable
               SharedSlot parent,
               @Nullable
               AbstractID groupID)

Base constructor for slots.

This is the old way of constructing slots by the legacy code

Parameters:

owner - The component from which this slot is allocated.

location - The location info of the TaskManager where the slot was allocated from

slotNumber - The number of this slot.

taskManagerGateway - The actor gateway to communicate with the TaskManager

parent - The parent slot that contains this slot. May be null, if this slot is the root.

groupID - The ID that identifies the task group for which this slot is allocated. May be null if the slot does not belong to any task group.

Slot

protected Slot(SlotContext slotContext,
               SlotOwner owner,
               int slotNumber,
               @Nullable
               SharedSlot parent,
               @Nullable
               AbstractID groupID)

Base constructor for slots.

Parameters:

slotContext - The slot context of this slot.

owner - The component from which this slot is allocated.

slotNumber - The number of this slot.

parent - The parent slot that contains this slot. May be null, if this slot is the root.

groupID - The ID that identifies the task group for which this slot is allocated. May be null if the slot does not belong to any task group.

Method Detail

getSlotContext

public SlotContext getSlotContext()

Gets the allocated slot that this slot refers to.

Returns:

This slot's allocated slot.

getTaskManagerID

public ResourceID getTaskManagerID()

Gets the ID of the TaskManager that offers this slot.

Returns:

The ID of the TaskManager that offers this slot

getTaskManagerLocation

public TaskManagerLocation getTaskManagerLocation()

Gets the location info of the TaskManager that offers this slot.

Returns:

The location info of the TaskManager that offers this slot

getTaskManagerGateway

public TaskManagerGateway getTaskManagerGateway()

Gets the actor gateway that can be used to send messages to the TaskManager.

This method should be removed once the new interface-based RPC abstraction is in place

Returns:

The actor gateway that can be used to send messages to the TaskManager.

getOwner

public SlotOwner getOwner()

Gets the owner of this slot. The owner is the component that the slot was created from and to which it needs to be returned after the executed tasks are done.

Returns:

The owner of this slot.

getSlotNumber

public int getSlotNumber()

Gets the number of the slot. For a simple slot, that is the number of the slot on its instance. For a non-root slot, this returns the number of the slot in the list amongst its siblings in the tree.

Returns:

The number of the slot on the instance or amongst its siblings that share the same slot.

getRootSlotNumber

public int getRootSlotNumber()

Gets the number of the root slot. This code behaves equal to getRoot().getSlotNumber(). If this slot is the root of the tree of shared slots, then this method returns the same value as getSlotNumber().

Returns:

The slot number of the root slot.

getGroupID

@Nullable
public AbstractID getGroupID()

Gets the ID that identifies the logical group to which this slot belongs:

• If the slot does not belong to any group in particular, this field is null.
• If this slot was allocated as a sub-slot of a SlotSharingGroupAssignment, then this ID will be the JobVertexID of the vertex whose task the slot holds in its shared slot.
• In case that the slot represents the shared slot of a co-location constraint, this ID will be the ID of the co-location constraint.

Returns:

The ID identifying the logical group of slots.

getParent

@Nullable
public SharedSlot getParent()

Gets the parent slot of this slot. Returns null, if this slot has no parent.

Returns:

The parent slot, or null, if no this slot has no parent.

getRoot

public Slot getRoot()

Gets the root slot of the tree containing this slot. If this slot is the root, the method returns this slot directly, otherwise it recursively goes to the parent until it reaches the root.

Returns:

The root slot of the tree containing this slot

getNumberLeaves

public abstract int getNumberLeaves()

Gets the number of simple slots that are at the leaves of the tree of slots.

Returns:

The number of simple slots at the leaves.

isAlive

public boolean isAlive()

Checks of the slot is still alive, i.e. in state ALLOCATED_AND_ALIVE.

Returns:

True if the slot is alive, false otherwise.

isCanceled

public boolean isCanceled()

Checks of the slot has been cancelled. Note that a released slot is also cancelled.

Returns:

True if the slot is cancelled or released, false otherwise.

isReleased

public boolean isReleased()

Checks of the slot has been released.

Returns:

True if the slot is released, false otherwise.

releaseSlot

public abstract CompletableFuture<?> releaseSlot(@Nullable
                                                 Throwable cause)

This method cancels and releases the slot and all its sub-slots. After this method completed successfully, the slot will be in state "released", and the isReleased() method will return true. If this slot is a simple slot, it will be returned to its instance. If it is a shared slot, it will release all of its sub-slots and release itself.

hashCode

public final int hashCode()

Slots must always has based on reference identity.

Overrides:

hashCode in class Object

equals

public final boolean equals(Object obj)

Slots must always compare on referential equality.

Overrides:

equals in class Object

toString

public String toString()

Overrides:

toString in class Object

hierarchy

protected String hierarchy()