org.apache.flink.runtime.state.hashmap

Class HashMapStateBackend

java.lang.Object

org.apache.flink.runtime.state.AbstractStateBackend

org.apache.flink.runtime.state.hashmap.HashMapStateBackend

All Implemented Interfaces:

Serializable, ConfigurableStateBackend, StateBackend

@PublicEvolving
public class HashMapStateBackend
extends AbstractStateBackend
implements ConfigurableStateBackend

This state backend holds the working state in the memory (JVM heap) of the TaskManagers and checkpoints based on the configured CheckpointStorage.

State Size Considerations

Working state is kept on the TaskManager heap. If a TaskManager executes multiple tasks concurrently (if the TaskManager has multiple slots, or if slot-sharing is used) then the aggregate state of all tasks needs to fit into that TaskManager's memory.

Configuration

As for all state backends, this backend can either be configured within the application (by creating the backend with the respective constructor parameters and setting it on the execution environment) or by specifying it in the Flink configuration.

If the state backend was specified in the application, it may pick up additional configuration parameters from the Flink configuration. For example, if the backend if configured in the application without a default savepoint directory, it will pick up a default savepoint directory specified in the Flink configuration of the running job/cluster. That behavior is implemented via the configure(ReadableConfig, ClassLoader) method.

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.flink.runtime.state.StateBackend

StateBackend.CustomInitializationMetrics, StateBackend.KeyedStateBackendParameters<K>, StateBackend.OperatorStateBackendParameters

Field Summary

Fields inherited from class org.apache.flink.runtime.state.AbstractStateBackend

latencyTrackingConfigBuilder

Constructor Summary

Constructors

Constructor and Description
HashMapStateBackend() Creates a new state backend.

Method Summary

Modifier and Type	Method and Description
HashMapStateBackend	configure(org.apache.flink.configuration.ReadableConfig config, ClassLoader classLoader) Creates a variant of the state backend that applies additional configuration parameters.
<K> AbstractKeyedStateBackend<K>	createKeyedStateBackend(StateBackend.KeyedStateBackendParameters<K> parameters) Creates a new CheckpointableKeyedStateBackend that is responsible for holding keyed state and checkpointing it.
OperatorStateBackend	createOperatorStateBackend(StateBackend.OperatorStateBackendParameters parameters) Creates a new OperatorStateBackend that can be used for storing operator state.
boolean	supportsNoClaimRestoreMode() Tells if a state backend supports the RestoreMode.NO_CLAIM mode.
boolean	supportsSavepointFormat(org.apache.flink.core.execution.SavepointFormatType formatType)

Methods inherited from class org.apache.flink.runtime.state.AbstractStateBackend

getCompressionDecorator

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.flink.runtime.state.StateBackend

getName, useManagedMemory

Constructor Detail

HashMapStateBackend

public HashMapStateBackend()

Creates a new state backend.

Method Detail

configure

public HashMapStateBackend configure(org.apache.flink.configuration.ReadableConfig config,
                                     ClassLoader classLoader)
                              throws org.apache.flink.configuration.IllegalConfigurationException

Description copied from interface: ConfigurableStateBackend

Creates a variant of the state backend that applies additional configuration parameters.

Settings that were directly done on the original state backend object in the application program typically have precedence over setting picked up from the configuration.

If no configuration is applied, or if the method directly applies configuration values to the (mutable) state backend object, this method may return the original state backend object. Otherwise it typically returns a modified copy.

Specified by:

configure in interface ConfigurableStateBackend

Parameters:

config - The configuration to pick the values from.

classLoader - The class loader that should be used to load the state backend.

Returns:

A reconfigured state backend.

Throws:

org.apache.flink.configuration.IllegalConfigurationException - Thrown if the configuration contained invalid entries.

supportsNoClaimRestoreMode

public boolean supportsNoClaimRestoreMode()

Description copied from interface: StateBackend

Tells if a state backend supports the RestoreMode.NO_CLAIM mode.

If a state backend supports NO_CLAIM mode, it should create an independent snapshot when it receives CheckpointType.FULL_CHECKPOINT in Snapshotable.snapshot(long, long, CheckpointStreamFactory, CheckpointOptions).

Specified by:

supportsNoClaimRestoreMode in interface StateBackend

Returns:

If the state backend supports RestoreMode.NO_CLAIM mode.

supportsSavepointFormat

public boolean supportsSavepointFormat(org.apache.flink.core.execution.SavepointFormatType formatType)

Specified by:

supportsSavepointFormat in interface StateBackend

createKeyedStateBackend

public <K> AbstractKeyedStateBackend<K> createKeyedStateBackend(StateBackend.KeyedStateBackendParameters<K> parameters)
                                                         throws IOException

Description copied from interface: StateBackend

Creates a new CheckpointableKeyedStateBackend that is responsible for holding keyed state and checkpointing it.

Keyed State is state where each value is bound to a key.

Specified by:

createKeyedStateBackend in interface StateBackend

Specified by:

createKeyedStateBackend in class AbstractStateBackend

Type Parameters:

K - The type of the keys by which the state is organized.

Parameters:

parameters - The arguments bundle for creating CheckpointableKeyedStateBackend.

Returns:

The Keyed State Backend for the given job, operator, and key group range.

Throws:

IOException

createOperatorStateBackend

public OperatorStateBackend createOperatorStateBackend(StateBackend.OperatorStateBackendParameters parameters)
                                                throws BackendBuildingException

Description copied from interface: StateBackend

Creates a new OperatorStateBackend that can be used for storing operator state.

Operator state is state that is associated with parallel operator (or function) instances, rather than with keys.

Specified by:

createOperatorStateBackend in interface StateBackend

Specified by:

createOperatorStateBackend in class AbstractStateBackend

Parameters:

parameters - The arguments bundle for creating OperatorStateBackend.

Returns:

The OperatorStateBackend for operator identified by the job and operator identifier.

Throws:

BackendBuildingException