groovyx.gpars.dataflow

Class LazyDataflowVariable<T>

java.lang.Object

groovyx.gpars.serial.WithSerialId

groovyx.gpars.dataflow.expression.DataflowExpression<T>

groovyx.gpars.dataflow.DataflowVariable<T>

groovyx.gpars.dataflow.LazyDataflowVariable<T>

Type Parameters:

T - Type of values to bind with the DataflowVariable

All Implemented Interfaces:

groovy.lang.GroovyObject, DataflowChannel<T>, DataflowReadChannel<T>, DataflowWriteChannel<T>, Promise<T>, SelectableChannel<T>, java.io.Serializable

public final class LazyDataflowVariable<T>
extends DataflowVariable<T>

Represents a thread-safe single-assignment, multi-read variable with delayed initialization. Each instance of DataflowVariable can be read repeatedly any time using the 'val' property and assigned once in its lifetime using the '<<' operator. Reads preceding assignment will be blocked until the value is assigned. For actors and Dataflow Operators the asynchronous non-blocking variants of the getValAsync() methods can be used. They register the request to read a value and will send a message to the actor or operator once the value is available.

Author:

Vaclav Pech Date: April 4, 2013

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class groovyx.gpars.dataflow.expression.DataflowExpression

DataflowExpression.BindDataflow<T>

Field Summary

Fields

Modifier and Type	Field and Description
private PGroup	group
private java.util.concurrent.atomic.AtomicBoolean	initializationStarted
private groovy.lang.Closure<T>	initializer

Fields inherited from class groovyx.gpars.dataflow.expression.DataflowExpression

error, S_INITIALIZED, S_INITIALIZING, S_NOT_INITIALIZED, state, stateUpdater, value, waitingUpdater

Fields inherited from class groovyx.gpars.serial.WithSerialId

serialHandle

Constructor Summary

Constructors

Constructor and Description
LazyDataflowVariable(groovy.lang.Closure<T> initializer) Creates a new unbound Lazy Dataflow Variable
LazyDataflowVariable(PGroup group, groovy.lang.Closure<T> initializer) Creates a new unbound Lazy Dataflow Variable with specific a PGroup to use for running the initializer

Method Summary

Modifier and Type	Method and Description
java.lang.Throwable	getError() Returns the error bound to the promise
T	getVal() Reads the value of the variable.
T	getVal(long timeout, java.util.concurrent.TimeUnit units) Reads the value of the variable.
void	getValAsync(MessageStream callback) Asynchronously retrieves the value of the variable.
void	getValAsync(java.lang.Object attachment, MessageStream callback) Used by Dataflow operators.
private void	initialize()
boolean	isError() Checks if the promise is bound to an error
<V> Promise<V>	then(groovy.lang.Closure<V> closure, groovy.lang.Closure<V> errorHandler) Schedule closure to be executed after data became available.
<V> Promise<V>	then(PGroup group, groovy.lang.Closure<V> closure, groovy.lang.Closure<V> errorHandler) Schedule closure to be executed after data becomes available.
<V> Promise<V>	then(Pool pool, groovy.lang.Closure<V> closure, groovy.lang.Closure<V> errorHandler) Schedule closure to be executed after data becomes available.
void	touch() May be used by lazy implementations to warm up

Methods inherited from class groovyx.gpars.dataflow.DataflowVariable

get, get, getRemoteClass, leftShift, leftShift, shouldThrowTimeout

Methods inherited from class groovyx.gpars.dataflow.expression.DataflowExpression

binaryChoice, binaryChoice, binaryChoice, binaryChoice, binaryChoice, binaryChoice, bind, bindError, bindSafely, bindUnique, chainWith, chainWith, chainWith, chainWith, chainWith, chainWith, choice, choice, choice, choice, choice, choice, doBindImpl, doBindRemote, evaluate, filter, filter, filter, filter, filter, filter, getBindErrorManager, getEventManager, getMetaClass, getProperty, into, into, into, into, into, into, invokeMethod, isBound, join, join, length, merge, merge, merge, merge, merge, merge, merge, merge, merge, merge, merge, merge, or, or, poll, rightShift, scheduleCallback, separate, separate, separate, separate, separate, separate, setMetaClass, setProperty, split, split, split, split, split, split, split, split, split, split, split, split, subscribe, subscribe, tap, tap, tap, tap, tap, tap, then, then, then, thenForkAndJoin, thenForkAndJoin, thenForkAndJoin, toString, transform, whenBound, whenBound, whenBound, whenBound, wheneverBound, wheneverBound

Methods inherited from class groovyx.gpars.serial.WithSerialId

createRemoteHandle, getOrCreateSerialHandle, writeReplace

Methods inherited from class java.lang.Object

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

Methods inherited from interface groovyx.gpars.dataflow.DataflowReadChannel

binaryChoice, binaryChoice, binaryChoice, binaryChoice, binaryChoice, binaryChoice, chainWith, chainWith, chainWith, chainWith, chainWith, chainWith, choice, choice, choice, choice, choice, choice, filter, filter, filter, filter, filter, filter, getEventManager, into, into, into, into, into, into, isBound, length, merge, merge, merge, merge, merge, merge, merge, merge, merge, merge, merge, merge, or, or, rightShift, separate, separate, separate, separate, separate, separate, split, split, split, split, split, split, split, split, split, split, split, split, tap, tap, tap, tap, tap, tap, then, then, then, whenBound, whenBound, whenBound, whenBound

Methods inherited from interface groovyx.gpars.dataflow.SelectableChannel

poll, wheneverBound, wheneverBound

Methods inherited from interface groovyx.gpars.dataflow.DataflowWriteChannel

bind

Methods inherited from interface groovyx.gpars.dataflow.Promise

isBound, join, join, rightShift, then, then, then, thenForkAndJoin, thenForkAndJoin, thenForkAndJoin, whenBound, whenBound, whenBound, whenBound

Field Detail

initializer

private final groovy.lang.Closure<T> initializer

initializationStarted

private final java.util.concurrent.atomic.AtomicBoolean initializationStarted

group

private final PGroup group

Constructor Detail

LazyDataflowVariable

public LazyDataflowVariable(groovy.lang.Closure<T> initializer)

Creates a new unbound Lazy Dataflow Variable

LazyDataflowVariable

public LazyDataflowVariable(PGroup group,
                            groovy.lang.Closure<T> initializer)

Creates a new unbound Lazy Dataflow Variable with specific a PGroup to use for running the initializer

Method Detail

initialize

private void initialize()

touch

public void touch()

Description copied from interface: Promise

May be used by lazy implementations to warm up

Specified by:

touch in interface Promise<T>

Overrides:

touch in class DataflowVariable<T>

isError

public final boolean isError()

Checks if the promise is bound to an error

Specified by:

isError in interface Promise<T>

Overrides:

isError in class DataflowVariable<T>

Returns:

True, if an error has been bound

getError

public final java.lang.Throwable getError()

Returns the error bound to the promise

Specified by:

getError in interface Promise<T>

Overrides:

getError in class DataflowVariable<T>

Returns:

The error

Throws:

java.lang.IllegalStateException - If not bound or not bound to an error

then

public final <V> Promise<V> then(groovy.lang.Closure<V> closure,
                                 groovy.lang.Closure<V> errorHandler)

Schedule closure to be executed after data became available. It is important to notice that even if the expression is already bound the execution of closure will not happen immediately but will be scheduled

Specified by:

then in interface Promise<T>

Overrides:

then in class DataflowVariable<T>

Parameters:

closure - closure to execute when data becomes available. The closure should take at most one argument.

errorHandler - closure to execute when an error (instance of Throwable) gets bound. The closure should take at most one argument.

Returns:

A promise for the results of the supplied closure. This allows for chaining of then() method calls.

then

public final <V> Promise<V> then(Pool pool,
                                 groovy.lang.Closure<V> closure,
                                 groovy.lang.Closure<V> errorHandler)

Schedule closure to be executed after data becomes available. It is important to notice that even if the expression is already bound the execution of closure will not happen immediately but will be scheduled.

Specified by:

then in interface Promise<T>

Overrides:

then in class DataflowVariable<T>

Parameters:

pool - The thread pool to use for task scheduling for asynchronous message delivery

closure - closure to execute when data becomes available. The closure should take at most one argument.

errorHandler - closure to execute when an error (instance of Throwable) gets bound. The closure should take at most one argument.

Returns:

A promise for the results of the supplied closure. This allows for chaining of then() method calls.

then

public final <V> Promise<V> then(PGroup group,
                                 groovy.lang.Closure<V> closure,
                                 groovy.lang.Closure<V> errorHandler)

Schedule closure to be executed after data becomes available. It is important to notice that even if the expression is already bound the execution of closure will not happen immediately but will be scheduled.

Specified by:

then in interface Promise<T>

Overrides:

then in class DataflowVariable<T>

Parameters:

group - The PGroup to use for task scheduling for asynchronous message delivery

closure - closure to execute when data becomes available. The closure should take at most one argument.

errorHandler - closure to execute when an error (instance of Throwable) gets bound. The closure should take at most one argument.

Returns:

A promise for the results of the supplied closure. This allows for chaining of then() method calls.

getVal

public T getVal()
         throws java.lang.InterruptedException

Description copied from class: DataflowExpression

Reads the value of the variable. Blocks, if the value has not been assigned yet.

Specified by:

getVal in interface DataflowReadChannel<T>

Overrides:

getVal in class DataflowExpression<T>

Returns:

The actual value

Throws:

java.lang.InterruptedException - If the current thread gets interrupted while waiting for the variable to be bound

getVal

public T getVal(long timeout,
                java.util.concurrent.TimeUnit units)
         throws java.lang.InterruptedException

Description copied from class: DataflowExpression

Reads the value of the variable. Blocks up to given timeout, if the value has not been assigned yet.

Specified by:

getVal in interface DataflowReadChannel<T>

Overrides:

getVal in class DataflowExpression<T>

Parameters:

timeout - The timeout value

units - Units for the timeout

Returns:

The actual value

Throws:

java.lang.InterruptedException - If the current thread gets interrupted while waiting for the variable to be bound

getValAsync

public void getValAsync(MessageStream callback)

Description copied from class: DataflowExpression

Asynchronously retrieves the value of the variable. Sends the actual value of the variable as a message back the the supplied actor once the value has been bound. The actor can perform other activities or release a thread back to the pool by calling react() waiting for the message with the value of the Dataflow Variable.

Specified by:

getValAsync in interface DataflowReadChannel<T>

Overrides:

getValAsync in class DataflowExpression<T>

Parameters:

callback - An actor to send the bound value to.

getValAsync

public void getValAsync(java.lang.Object attachment,
                        MessageStream callback)

Description copied from class: DataflowExpression

Used by Dataflow operators. Asynchronously retrieves the value of the variable. Sends a message back the the supplied MessageStream with a map holding the supplied attachment under the 'attachment' key and the actual value of the variable under the 'result' key once the value has been bound. Attachment is an arbitrary value helping the actor.operator match its request with the reply. The actor/operator can perform other activities or release a thread back to the pool by calling react() waiting for the message with the value of the Dataflow Variable.

Specified by:

getValAsync in interface DataflowReadChannel<T>

Overrides:

getValAsync in class DataflowExpression<T>

Parameters:

attachment - arbitrary non-null attachment if reader needs better identification of result

callback - An actor to send the bound value plus the supplied index to.