org.apache.reef.io

Interface Spool<T>

All Superinterfaces:

Accumulable<T>, Iterable<T>

All Known Implementing Classes:

RamSpool, SerializerFileSpool, SortingRamSpool

public interface Spool<T>
extends Iterable<T>, Accumulable<T>

Spool files can be appended to, and can be scanned starting at the beginning. Random read and write access is not supported. Spool files are ephemeral; the space they use will be automatically reclaimed by REEF.

Method Summary

Methods

Modifier and Type	Method and Description
Accumulator<T>	accumulator() Returns an Accumulator for the spool file.
Iterator<T>	iterator() Returns an Iterable over the spool file.

Method Detail

iterator

Iterator<T> iterator()

Returns an Iterable over the spool file.

Depending on the implementation, this method may be called only once per Spool instance, or it may be called repeatedly. Similarly, with some Spool implementations, attempts to append to the SpoolFile after calling iterator() may fail fast with a ConcurrentModificationException.

Specified by:

iterator in interface Iterable<T>

Returns:

An Iterator over the SpoolFile, in the order data was inserted.

Throws:

Exception

accumulator

Accumulator<T> accumulator()
                           throws ServiceException

Returns an Accumulator for the spool file.

Depending on the implementation, this method may be called only once per Spool instance, or it may be called repeatedly. Similarly, with some Spool implementations, attempts to append to the SpoolFile after calling iterator() may fail fast with a ConcurrentModificationException.

Specified by:

accumulator in interface Accumulable<T>

Returns:

the new Accumulator

Throws:

ServiceException