com.hazelcast.jet.pipeline

Class ContextFactory<C>

java.lang.Object

com.hazelcast.jet.pipeline.ContextFactory<C>

Type Parameters:

C - the user-defined context object type

All Implemented Interfaces:

Serializable

public final class ContextFactory<C>
extends Object
implements Serializable

A holder of functions needed to create and destroy a context object that can be used in the Pipeline API to give the transforming functions (map, filter, flatMap) access to some resource that would be too expensive to acquire-release on each function call. It also provides access to the local JetInstance. Among others, this gives you the ability to interact with IMDG data structures such as IMap and ReplicatedMap during the transformation.

You can use the context factory from these Pipeline API methods:

• GeneralStage.mapUsingContext(com.hazelcast.jet.pipeline.ContextFactory<C>, com.hazelcast.jet.function.DistributedBiFunction<? super C, ? super T, ? extends R>)
• GeneralStage.filterUsingContext(com.hazelcast.jet.pipeline.ContextFactory<C>, com.hazelcast.jet.function.DistributedBiPredicate<? super C, ? super T>)
• GeneralStage.flatMapUsingContext(com.hazelcast.jet.pipeline.ContextFactory<C>, com.hazelcast.jet.function.DistributedBiFunction<? super C, ? super T, ? extends com.hazelcast.jet.Traverser<? extends R>>)

To get a context factory, choose one of the predefined factories in ContextFactories or create your own using the builder you get by calling withCreateFn(com.hazelcast.jet.function.DistributedFunction<com.hazelcast.jet.JetInstance, ? extends C>). The factory instances must be immutable.

See Also:

Serialized Form

Method Summary

Modifier and Type	Method and Description
DistributedFunction<JetInstance,? extends C>	createFn() Returns the create-function.
DistributedConsumer<? super C>	destroyFn() Returns the destroy-function.
boolean	isCooperative() Returns the isCooperative flag.
boolean	isSharedLocally() Returns the isSharedLocally flag.
ContextFactory<C>	nonCooperative() Returns a copy of this ContextFactory with the isCooperative flag set to false.
ContextFactory<C>	shareLocally() Returns a copy of this ContextFactory with the shareLocally flag set to true.
static <C> ContextFactory<C>	withCreateFn(DistributedFunction<JetInstance,? extends C> createContextFn) Creates a new ContextFactory with the given create-function.
ContextFactory<C>	withDestroyFn(DistributedConsumer<? super C> destroyFn) Returns a copy of this ContextFactory with the destory-function replaced with the given function.

Methods inherited from class java.lang.Object

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

Method Detail

withCreateFn

@Nonnull
public static <C> ContextFactory<C> withCreateFn(@Nonnull
                                                          DistributedFunction<JetInstance,? extends C> createContextFn)

Creates a new ContextFactory with the given create-function.

Type Parameters:

C - the user-defined context object type

Parameters:

createContextFn - the function to create new context object, given a JetInstance

Returns:

a new factory instance

withDestroyFn

@Nonnull
public ContextFactory<C> withDestroyFn(@Nonnull
                                                DistributedConsumer<? super C> destroyFn)

Returns a copy of this ContextFactory with the destory-function replaced with the given function.

Parameters:

destroyFn - the function to destroy user-defined context. It will be called when the job finishes

Returns:

a copy of this factory with the supplied destroy-function

nonCooperative

@Nonnull
public ContextFactory<C> nonCooperative()

Returns a copy of this ContextFactory with the isCooperative flag set to false. The context factory is cooperative by default. Call this method if any of the calls to the methods in the context may block or otherwise take long to complete.

The contract of cooperative multithreading is described here.

Returns:

a copy of this factory with the isCooperative flag set to false.

shareLocally

@Nonnull
public ContextFactory<C> shareLocally()

Returns a copy of this ContextFactory with the shareLocally flag set to true. By default the context object is not shared so each parallel processor gets its own instance. If you enable sharing, the context object will be used from multiple threads — make sure that it is thread-safe.

Returns:

a copy of this factory with the isSharedLocally flag set.

createFn

@Nonnull
public DistributedFunction<JetInstance,? extends C> createFn()

Returns the create-function.

destroyFn

@Nonnull
public DistributedConsumer<? super C> destroyFn()

Returns the destroy-function.

isCooperative

public boolean isCooperative()

Returns the isCooperative flag.

isSharedLocally

public boolean isSharedLocally()

Returns the isSharedLocally flag.