BigQueue (bigqueue 1.7.0.5 API)

java.lang.Object
- com.bluejeans.common.bigqueue.BigQueue

All Implemented Interfaces:

Closeable, AutoCloseable
```
public class BigQueue
extends Object
implements Closeable
```
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

Constructor Summary

Constructors
Constructor and Description
`BigQueue(String queueDir, String queueName)` A big, fast and persistent queue implementation, use default back data page size, see `BigArray.DEFAULT_DATA_PAGE_SIZE`
`BigQueue(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(ItemIterator iterator)`
`void`	`close()`
`byte[]`	`dequeue()` Retrieves and removes the front of a queue
`com.google.common.util.concurrent.ListenableFuture<byte[]>`	`dequeueAsync()` Retrieves a Future which will complete if new Items where enqued.
`List<byte[]>`	`dequeueMulti(int max)` Retrieves and removes the fronts of a queue upto given total number / total size whichever is smaller
`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
`com.google.common.util.concurrent.ListenableFuture<byte[]>`	`peekAsync()` Retrieves the item at the front of a queue asynchronously.
`List<byte[]>`	`peekMulti(int max)` Retrieves the items at the front of a queue
`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
  - BigQueue
```
public BigQueue(String queueDir,
                String queueName)
```
    A big, fast and persistent queue implementation, use default back data page size, see BigArray.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
  - BigQueue
```
public BigQueue(String queueDir,
                String queueName,
                int pageSize)
```
    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 BigArray.MINIMUM_DATA_PAGE_SIZE
- Method Detail
  - isEmpty
```
public boolean isEmpty()
```
    Determines whether a queue is empty
    
    Returns:
    
    ture if empty, false otherwise
  - enqueue
```
public void enqueue(byte[] data)
```
    Adds an item at the back of a queue
    
    Parameters:
    
    data - to be enqueued data
  - dequeue
```
public byte[] dequeue()
```
    Retrieves and removes the front of a queue
    
    Returns:
    
    data at the front of a queue
  - dequeueMulti
```
public List<byte[]> dequeueMulti(int max)
```
    Retrieves and removes the fronts of a queue upto given total number / total size whichever is smaller
    
    Parameters:
    
    max - the maximum to dequque
    
    Returns:
    
    data at the fronts of a queue
  - dequeueAsync
```
public com.google.common.util.concurrent.ListenableFuture<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
```
public void removeAll()
```
    Removes all items of a queue, this will empty the queue and delete all back data files.
  - peek
```
public byte[] peek()
```
    Retrieves the item at the front of a queue
    
    Returns:
    
    data at the front of a queue
  - peekMulti
```
public List<byte[]> peekMulti(int max)
```
    Retrieves the items at the front of a queue
    
    Parameters:
    
    max - the maximum elements to peek
    
    Returns:
    
    data at the front of a queue
  - peekAsync
```
public com.google.common.util.concurrent.ListenableFuture<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
```
public void applyForEach(ItemIterator iterator)
```
  - close
```
public void close()
           throws IOException
```
    Specified by:
    
    close in interface Closeable
    
    Specified by:
    
    close in interface AutoCloseable
    
    Throws:
    
    IOException
  - gc
```
public void gc()
```
    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.
  - flush
```
public 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
```
public long size()
```
    Total number of items available in the queue.
    
    Returns:
    
    total number

Class BigQueue

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

BigQueue

BigQueue

Method Detail

isEmpty

enqueue

dequeue

dequeueMulti

dequeueAsync

removeAll

peek

peekMulti

peekAsync

applyForEach

close

gc

flush

size