org.kairosdb.bigqueue

Interface IBigQueue

All Superinterfaces:

AutoCloseable, Closeable

All Known Implementing Classes:

BigQueueImpl

public interface IBigQueue
extends Closeable

Queue ADT

Author:

bulldog

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	IBigQueue.ItemIterator Item iterator interface

Method Summary

Modifier and Type	Method and Description
void	applyForEach(IBigQueue.ItemIterator iterator) apply an implementation of a ItemIterator interface for each queue item
byte[]	dequeue() Retrieves and removes the front of a queue
CompletableFuture<byte[]>	dequeueAsync() Retrieves a Future which will complete if new Items where enqued.
void	enqueue(byte[] data) Adds an item at the back of a queue
void	flush() Force to persist current state of the queue, normally, you don't need to flush explicitly since: 1.) BigQueue will automatically flush a cached page when it is replaced out, 2.) BigQueue uses memory mapped file technology internally, and the OS will flush the changes even your process crashes, call this periodically only if you need transactional reliability and you are aware of the cost to performance.
void	gc() Delete all used data files to free disk space.
boolean	isEmpty() Determines whether a queue is empty
byte[]	peek() Retrieves the item at the front of a queue
CompletableFuture<byte[]>	peekAsync() Retrieves the item at the front of a queue asynchronously.
void	removeAll() Removes all items of a queue, this will empty the queue and delete all back data files.
long	size() Total number of items available in the queue.

Methods inherited from interface java.io.Closeable

close

Method Detail

isEmpty

boolean isEmpty()

Determines whether a queue is empty

Returns:

ture if empty, false otherwise

enqueue

void enqueue(byte[] data)
      throws IOException

Adds an item at the back of a queue

Parameters:

data - to be enqueued data

Throws:

IOException - exception throws if there is any IO error during enqueue operation.

dequeue

byte[] dequeue()
        throws IOException

Retrieves and removes the front of a queue

Returns:

data at the front of a queue

Throws:

IOException - exception throws if there is any IO error during dequeue operation.

dequeueAsync

CompletableFuture<byte[]> dequeueAsync()

Retrieves a Future which will complete if new Items where enqued. Use this method to retrieve a future where to register as Listener instead of repeatedly polling the queues state. On complete this future contains the result of the dequeue operation. Hence the item was automatically removed from the queue.

Returns:

a ListenableFuture which completes with the first entry if items are ready to be dequeued.

removeAll

void removeAll()
        throws IOException

Removes all items of a queue, this will empty the queue and delete all back data files.

Throws:

IOException - exception throws if there is any IO error during dequeue operation.

peek

byte[] peek()
     throws IOException

Retrieves the item at the front of a queue

Returns:

data at the front of a queue

Throws:

IOException - exception throws if there is any IO error during peek operation.

peekAsync

CompletableFuture<byte[]> peekAsync()

Retrieves the item at the front of a queue asynchronously. On complete the value set in this future is the result of the peek operation. Hence the item remains at the front of the list.

Returns:

a future containing the first item if available. You may register as listener at this future to be informed if a new item arrives.

applyForEach

void applyForEach(IBigQueue.ItemIterator iterator)
           throws IOException

apply an implementation of a ItemIterator interface for each queue item

Parameters:

iterator - Callback used for each item in array.

Throws:

IOException - exception thrown if IO error occurs

gc

void gc()
 throws IOException

Delete all used data files to free disk space. BigQueue will persist enqueued data in disk files, these data files will remain even after the data in them has been dequeued later, so your application is responsible to periodically call this method to delete all used data files and free disk space.

Throws:

IOException - exception throws if there is any IO error during gc operation.

flush

void flush()

Force to persist current state of the queue, normally, you don't need to flush explicitly since: 1.) BigQueue will automatically flush a cached page when it is replaced out, 2.) BigQueue uses memory mapped file technology internally, and the OS will flush the changes even your process crashes, call this periodically only if you need transactional reliability and you are aware of the cost to performance.

size

long size()

Total number of items available in the queue.

Returns:

total number