ai.grakn.engine.attribute.deduplicator.queue

Class RocksDbQueue

java.lang.Object

ai.grakn.engine.attribute.deduplicator.queue.RocksDbQueue

All Implemented Interfaces:

AutoCloseable

public class RocksDbQueue
extends Object
implements AutoCloseable

An implementation of a FIFO queue to support the attribute de-duplication in RocksDB. It supports three operations: insert, read, and ack. The read and ack should be used together in order to provide fault-tolerance. The attribute de-duplicator can read attributes from the queue and only ack after everything has been processed. If the de-duplicator crashes during a deduplication, it can resume operation from the last ack-ed attribute.

Author:

Ganeshwara Herawan Hananda

Constructor Summary

Constructors

Constructor and Description
RocksDbQueue(Path path) Instantiates the class and the queue data directory

Method Summary

Modifier and Type	Method and Description
void	ack(List<Attribute> attributes) Remove attributes from the queue.
void	close() Close the RocksDbQueue instance.
void	insert(Attribute attribute) insert a new attribute at the end of the queue.
List<Attribute>	read(int limit) Read at most N attributes from the beginning of the queue.

Methods inherited from class java.lang.Object

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

Constructor Detail

RocksDbQueue

public RocksDbQueue(Path path)

Instantiates the class and the queue data directory

Parameters:

path - where to persist the queue data

Method Detail

insert

public void insert(Attribute attribute)

insert a new attribute at the end of the queue.

Parameters:

attribute - the attribute to be inserted

read

public List<Attribute> read(int limit)
                     throws InterruptedException

Read at most N attributes from the beginning of the queue. Read everything if there are less than N attributes in the queue. If the queue is empty, the method will block until the queue receives a new attribute. The attributes won't be removed from the queue until you call #ack(List) on the returned attributes.

Parameters:

limit - the maximum number of items to be returned.

Returns:

a list of Attribute

Throws:

InterruptedException

See Also:

#ack(List)

ack

public void ack(List<Attribute> attributes)

Remove attributes from the queue.

Parameters:

attributes - the attributes which will be removed

close

public void close()

Close the RocksDbQueue instance.

Specified by:

close in interface AutoCloseable