org.apache.flink.statefun.flink.core.backpressure

Class ThresholdBackPressureValve

java.lang.Object

org.apache.flink.statefun.flink.core.backpressure.ThresholdBackPressureValve

All Implemented Interfaces:

BackPressureValve

public final class ThresholdBackPressureValve
extends java.lang.Object
implements BackPressureValve

A simple Threshold based BackPressureValve.

There are two cases where a backpressure would be triggered:

• The total number of in-flight async operations in a StreamTask exceeds a predefined threshold. This is tracked by pendingAsynchronousOperationsCount, it is incremented when an async operation is registered, and decremented when it is completed.
• A specific address has requested to stop processing new inputs, this is tracked by the blockedAddressSet. The method notifyAsyncOperationCompleted(Address) is meant to be called when ANY async operation has been completed.

Constructor Summary

Constructors

Constructor and Description
ThresholdBackPressureValve(int maximumPendingAsynchronousOperations) Constructs a ThresholdBackPressureValve.

Method Summary

Modifier and Type	Method and Description
void	blockAddress(Address address) Requests to stop processing any further input for that address, as long as there is an uncompleted async operation (registered by @address).
boolean	isAddressBlocked(Address address) Checks whether a given address was previously blocked with BackPressureValve.blockAddress(Address).
void	notifyAsyncOperationCompleted(Address owningAddress) Notifies when a async operation, registered by @owningAddress was completed.
void	notifyAsyncOperationRegistered() Notifies the back pressure mechanism that a async operation was registered via Context.registerAsyncOperation(Object, CompletableFuture).
boolean	shouldBackPressure() Indicates rather a back pressure is needed.

Methods inherited from class java.lang.Object

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

Constructor Detail

ThresholdBackPressureValve

public ThresholdBackPressureValve(int maximumPendingAsynchronousOperations)

Constructs a ThresholdBackPressureValve.

Parameters:

maximumPendingAsynchronousOperations - the total allowed async operations to be inflight per StreamTask, or -1 to disable back pressure.

Method Detail

shouldBackPressure

public boolean shouldBackPressure()

Indicates rather a back pressure is needed.

Specified by:

shouldBackPressure in interface BackPressureValve

Returns:

true if a back pressure should be applied.

blockAddress

public void blockAddress(Address address)

Requests to stop processing any further input for that address, as long as there is an uncompleted async operation (registered by @address).

NOTE: The address would unblocked as soon as some (one) async operation registered by that address completes.

Specified by:

blockAddress in interface BackPressureValve

Parameters:

address - the address

notifyAsyncOperationRegistered

public void notifyAsyncOperationRegistered()

Notifies the back pressure mechanism that a async operation was registered via Context.registerAsyncOperation(Object, CompletableFuture).

Specified by:

notifyAsyncOperationRegistered in interface BackPressureValve

notifyAsyncOperationCompleted

public void notifyAsyncOperationCompleted(Address owningAddress)

Notifies when a async operation, registered by @owningAddress was completed.

Specified by:

notifyAsyncOperationCompleted in interface BackPressureValve

Parameters:

owningAddress - the owner of the completed async operation.

isAddressBlocked

public boolean isAddressBlocked(Address address)

Checks whether a given address was previously blocked with BackPressureValve.blockAddress(Address).

Specified by:

isAddressBlocked in interface BackPressureValve

Parameters:

address - the address to check

Returns:

boolean indicating whether or not the address was blocked.