BigQueueImpl (bigqueue 1.0.0 API)

java.lang.Object
- org.kariosdb.bigqueue.BigQueueImpl

All Implemented Interfaces:

Closeable, AutoCloseable, IBigQueue
```
public class BigQueueImpl
extends Object
implements IBigQueue
```
A big, fast and persistent queue implementation. Main features: 1. FAST : close to the speed of direct memory access, both enqueue and dequeue are close to O(1) memory access. 2. MEMORY-EFFICIENT : automatic paging and swapping algorithm, only most-recently accessed data is kept in memory. 3. THREAD-SAFE : multiple threads can concurrently enqueue and dequeue without data corruption. 4. PERSISTENT - all data in queue is persisted on disk, and is crash resistant. 5. BIG(HUGE) - the total size of the queued data is only limited by the available disk space.

Author:

bulldog

Nested Class Summary
- Nested classes/interfaces inherited from interface org.kariosdb.bigqueue.IBigQueue
  IBigQueue.ItemIterator

Constructor Summary

Constructors
Constructor and Description
`BigQueueImpl(String queueDir, String queueName)` A big, fast and persistent queue implementation, use default back data page size, see `BigArrayImpl.DEFAULT_DATA_PAGE_SIZE`
`BigQueueImpl(String queueDir, String queueName, int pageSize)` A big, fast and persistent queue implementation.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`applyForEach(IBigQueue.ItemIterator iterator)` apply an implementation of a ItemIterator interface for each queue item
`void`	`close()`
`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 class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - BigQueueImpl
```
public BigQueueImpl(String queueDir,
                    String queueName)
             throws IOException
```
    A big, fast and persistent queue implementation, use default back data page size, see BigArrayImpl.DEFAULT_DATA_PAGE_SIZE
    
    Parameters:
    
    queueDir - the directory to store queue data
    
    queueName - the name of the queue, will be appended as last part of the queue directory
    
    Throws:
    
    IOException - exception throws if there is any IO error during queue initialization
  - BigQueueImpl
```
public BigQueueImpl(String queueDir,
                    String queueName,
                    int pageSize)
             throws IOException
```
    A big, fast and persistent queue implementation.
    
    Parameters:
    
    queueDir - the directory to store queue data
    
    queueName - the name of the queue, will be appended as last part of the queue directory
    
    pageSize - the back data file size per page in bytes, see minimum allowed BigArrayImpl.MINIMUM_DATA_PAGE_SIZE
    
    Throws:
    
    IOException - exception throws if there is any IO error during queue initialization
- Method Detail
  - isEmpty
```
public boolean isEmpty()
```
    Description copied from interface: IBigQueue
    
    Determines whether a queue is empty
    
    Specified by:
    
    isEmpty in interface IBigQueue
    
    Returns:
    
    ture if empty, false otherwise
  - enqueue
```
public void enqueue(byte[] data)
             throws IOException
```
    Description copied from interface: IBigQueue
    
    Adds an item at the back of a queue
    
    Specified by:
    
    enqueue in interface IBigQueue
    
    Parameters:
    
    data - to be enqueued data
    
    Throws:
    
    IOException - exception throws if there is any IO error during enqueue operation.
  - dequeue
```
public byte[] dequeue()
               throws IOException
```
    Description copied from interface: IBigQueue
    
    Retrieves and removes the front of a queue
    
    Specified by:
    
    dequeue in interface IBigQueue
    
    Returns:
    
    data at the front of a queue
    
    Throws:
    
    IOException - exception throws if there is any IO error during dequeue operation.
  - dequeueAsync
```
public CompletableFuture<byte[]> dequeueAsync()
```
    Description copied from interface: IBigQueue
    
    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.
    
    Specified by:
    
    dequeueAsync in interface IBigQueue
    
    Returns:
    
    a ListenableFuture which completes with the first entry if items are ready to be dequeued.
  - removeAll
```
public void removeAll()
               throws IOException
```
    Description copied from interface: IBigQueue
    
    Removes all items of a queue, this will empty the queue and delete all back data files.
    
    Specified by:
    
    removeAll in interface IBigQueue
    
    Throws:
    
    IOException - exception throws if there is any IO error during dequeue operation.
  - peek
```
public byte[] peek()
            throws IOException
```
    Description copied from interface: IBigQueue
    
    Retrieves the item at the front of a queue
    
    Specified by:
    
    peek in interface IBigQueue
    
    Returns:
    
    data at the front of a queue
    
    Throws:
    
    IOException - exception throws if there is any IO error during peek operation.
  - peekAsync
```
public CompletableFuture<byte[]> peekAsync()
```
    Description copied from interface: IBigQueue
    
    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.
    
    Specified by:
    
    peekAsync in interface IBigQueue
    
    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
```
public void applyForEach(IBigQueue.ItemIterator iterator)
                  throws IOException
```
    apply an implementation of a ItemIterator interface for each queue item
    
    Specified by:
    
    applyForEach in interface IBigQueue
    
    Parameters:
    
    iterator - Callback used for each item in array.
    
    Throws:
    
    IOException - exception thrown if IO error occurs
  - close
```
public void close()
           throws IOException
```
    Specified by:
    
    close in interface Closeable
    
    Specified by:
    
    close in interface AutoCloseable
    
    Throws:
    
    IOException
  - gc
```
public void gc()
        throws IOException
```
    Description copied from interface: IBigQueue
    
    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.
    
    Specified by:
    
    gc in interface IBigQueue
    
    Throws:
    
    IOException - exception throws if there is any IO error during gc operation.
  - flush
```
public void flush()
```
    Description copied from interface: IBigQueue
    
    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.
    
    Specified by:
    
    flush in interface IBigQueue
  - size
```
public long size()
```
    Description copied from interface: IBigQueue
    
    Total number of items available in the queue.
    
    Specified by:
    
    size in interface IBigQueue
    
    Returns:
    
    total number

Class BigQueueImpl

Nested Class Summary

Nested classes/interfaces inherited from interface org.kariosdb.bigqueue.IBigQueue

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

BigQueueImpl

BigQueueImpl

Method Detail

isEmpty

enqueue

dequeue

dequeueAsync

removeAll

peek

peekAsync

applyForEach

close

gc

flush

size