org.apache.druid.segment.loading

Class RoundRobinStorageLocationSelectorStrategy

java.lang.Object

org.apache.druid.segment.loading.RoundRobinStorageLocationSelectorStrategy

All Implemented Interfaces:

StorageLocationSelectorStrategy

public class RoundRobinStorageLocationSelectorStrategy
extends Object
implements StorageLocationSelectorStrategy

A StorageLocation selector strategy that selects a segment cache location in a round-robin fashion each time among the available storage locations. When Iterator.next() on iterator retuned by getLocations() is called the locations are returned in a round robin fashion even when multiple threads are in use.

Constructor Summary

Constructors

Constructor and Description
RoundRobinStorageLocationSelectorStrategy(List<StorageLocation> storageLocations)

Method Summary

Modifier and Type	Method and Description
Iterator<StorageLocation>	getLocations() Finds the best ordering of the StorageLocations to load a DataSegment according to the location selector strategy.

Methods inherited from class java.lang.Object

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

Constructor Detail

RoundRobinStorageLocationSelectorStrategy

public RoundRobinStorageLocationSelectorStrategy(List<StorageLocation> storageLocations)

Method Detail

getLocations

public Iterator<StorageLocation> getLocations()

Description copied from interface: StorageLocationSelectorStrategy

Finds the best ordering of the StorageLocations to load a DataSegment according to the location selector strategy. This method returns an iterator instead of a single best location. The caller is responsible for iterating over the locations and calling StorageLocation.reserve(java.lang.String, org.apache.druid.timeline.DataSegment) method. This is because a single location may be problematic like failed disk or might become unwritable for whatever reasons. This method can be called by different threads and so should be thread-safe.

Specified by:

getLocations in interface StorageLocationSelectorStrategy

Returns:

An iterator of StorageLocations from which the callers can iterate and pick a location.