FanOutQueue (bigqueue 1.7.0.5 API)

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

All Implemented Interfaces:

Closeable, AutoCloseable
```
public class FanOutQueue
extends Object
implements Closeable
```
A big, fast and persistent queue implementation supporting fan out semantics. 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. 6. FANOUT - support fan out semantics, multiple consumers can independently consume a single queue without intervention, everyone has its own queue front index. 7. CLIENT MANAGED INDEX - support access by index and the queue index is managed at client side.

Author:

bulldog

Field Summary

Fields
Modifier and Type Field and Description

static long EARLIEST
Constant represents earliest timestamp

static long LATEST
Constant represents latest timestamp

Fields
Modifier and Type	Field and Description
`static long`	`EARLIEST` Constant represents earliest timestamp
`static long`	`LATEST` Constant represents latest timestamp

Constructor Summary

Constructors
Constructor and Description
`FanOutQueue(String queueDir, String queueName)` A big, fast and persistent queue implementation with fanout support, use default back data page size, see `BigArray.DEFAULT_DATA_PAGE_SIZE`
`FanOutQueue(String queueDir, String queueName, int pageSize)` A big, fast and persistent queue implementation with fandout support.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`close()`
`byte[]`	`dequeue(String fanoutId)` Retrieves and removes the front of a fan out queue
`long`	`enqueue(byte[] data)` Adds an item at the back of the queue
`long`	`findClosestIndex(long timestamp)` Find an index closest to the specific timestamp when the corresponding item was enqueued.
`void`	`flush()` Force to persist current state of the queue, normally, you don't need to flush explicitly since: 1.) FanOutQueue will automatically flush a cached page when it is replaced out, 2.) FanOutQueue 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.
`byte[]`	`get(long index)` Retrieves data item at the specific index of the queue
`long`	`getBackFileSize()` Current total size of the back files of this queue
`long`	`getFrontIndex()` Get the queue front index, this is the earliest appended index
`long`	`getFrontIndex(String fanoutId)`
`int`	`getLength(long index)` Get length of data item at specific index of the queue
`long`	`getRearIndex()` Get the queue rear index, this is the next to be appended index
`long`	`getTimestamp(long index)` Get timestamp of data item at specific index of the queue, this is the timestamp when corresponding item was appended into the queue.
`boolean`	`isEmpty()` Determines whether the queue is empty
`boolean`	`isEmpty(String fanoutId)`
`void`	`limitBackFileSize(long sizeLimit)` Limit the back file size of this queue, truncate back files and advance the queue front if necessary.
`byte[]`	`peek(String fanoutId)` Peek the item at the front of a fanout queue, without removing it from the queue
`int`	`peekLength(String fanoutId)` Peek the length of the item at the front of a fan out queue
`long`	`peekTimestamp(String fanoutId)` Peek the timestamp of the item at the front of a fan out queue
`void`	`removeAll()`
`void`	`removeBefore(long timestamp)` Remove all data before specific timestamp, truncate back files and advance the queue front if necessary.
`void`	`resetQueueFrontIndex(String fanoutId, long index)`
`long`	`size()` Total number of items remaining in the queue.
`long`	`size(String fanoutId)`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - EARLIEST
```
public static final long EARLIEST
```
    Constant represents earliest timestamp
    
    See Also:
    
    Constant Field Values
  - LATEST
```
public static final long LATEST
```
    Constant represents latest timestamp
    
    See Also:
    
    Constant Field Values
- Constructor Detail
  - FanOutQueue
```
public FanOutQueue(String queueDir,
                   String queueName,
                   int pageSize)
```
    A big, fast and persistent queue implementation with fandout support.
    
    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
  - FanOutQueue
```
public FanOutQueue(String queueDir,
                   String queueName)
```
    A big, fast and persistent queue implementation with fanout support, 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
- Method Detail
  - isEmpty
```
public boolean isEmpty(String fanoutId)
```
  - isEmpty
```
public boolean isEmpty()
```
    Determines whether the queue is empty
    
    Returns:
    
    true if empty, false otherwise
  - enqueue
```
public long enqueue(byte[] data)
```
    Adds an item at the back of the queue
    
    Parameters:
    
    data - to be enqueued data
    
    Returns:
    
    index where the item was appended
  - dequeue
```
public byte[] dequeue(String fanoutId)
```
    Retrieves and removes the front of a fan out queue
    
    Parameters:
    
    fanoutId - the fanout identifier
    
    Returns:
    
    data at the front of a queue
  - peek
```
public byte[] peek(String fanoutId)
```
    Peek the item at the front of a fanout queue, without removing it from the queue
    
    Parameters:
    
    fanoutId - the fanout identifier
    
    Returns:
    
    data at the front of a queue
  - peekLength
```
public int peekLength(String fanoutId)
```
    Peek the length of the item at the front of a fan out queue
    
    Parameters:
    
    fanoutId - the fanout identifier
    
    Returns:
    
    data at the front of a queue
  - peekTimestamp
```
public long peekTimestamp(String fanoutId)
```
    Peek the timestamp of the item at the front of a fan out queue
    
    Parameters:
    
    fanoutId - the fanout identifier
    
    Returns:
    
    data at the front of a queue
  - get
```
public byte[] get(long index)
```
    Retrieves data item at the specific index of the queue
    
    Parameters:
    
    index - data item index
    
    Returns:
    
    data at index
  - getLength
```
public int getLength(long index)
```
    Get length of data item at specific index of the queue
    
    Parameters:
    
    index - data item index
    
    Returns:
    
    length of data item
  - getTimestamp
```
public long getTimestamp(long index)
```
    Get timestamp of data item at specific index of the queue, this is the timestamp when corresponding item was appended into the queue.
    
    Parameters:
    
    index - data item index
    
    Returns:
    
    timestamp of data item
  - removeBefore
```
public void removeBefore(long timestamp)
```
    Remove all data before specific timestamp, truncate back files and advance the queue front if necessary.
    
    Parameters:
    
    timestamp - a timestamp
  - limitBackFileSize
```
public void limitBackFileSize(long sizeLimit)
```
    Limit the back file size of this queue, truncate back files and advance the queue front if necessary. Note, this is a best effort call, exact size limit can't be guaranteed
    
    Parameters:
    
    sizeLimit - size limit
  - getBackFileSize
```
public long getBackFileSize()
```
    Current total size of the back files of this queue
    
    Returns:
    
    total back file size
  - findClosestIndex
```
public long findClosestIndex(long timestamp)
```
    Find an index closest to the specific timestamp when the corresponding item was enqueued. to find latest index, use LATEST as timestamp. to find earliest index, use EARLIEST as timestamp.
    
    Parameters:
    
    timestamp - when the corresponding item was appended
    
    Returns:
    
    an index
  - resetQueueFrontIndex
```
public void resetQueueFrontIndex(String fanoutId,
                                 long index)
```
  - size
```
public long size(String fanoutId)
```
  - size
```
public long size()
```
    Total number of items remaining in the queue.
    
    Returns:
    
    total number
  - flush
```
public void flush()
```
    Force to persist current state of the queue, normally, you don't need to flush explicitly since: 1.) FanOutQueue will automatically flush a cached page when it is replaced out, 2.) FanOutQueue 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.
  - close
```
public void close()
```
    Specified by:
    
    close in interface Closeable
    
    Specified by:
    
    close in interface AutoCloseable
  - removeAll
```
public void removeAll()
```
  - getFrontIndex
```
public long getFrontIndex()
```
    Get the queue front index, this is the earliest appended index
    
    Returns:
    
    an index
  - getRearIndex
```
public long getRearIndex()
```
    Get the queue rear index, this is the next to be appended index
    
    Returns:
    
    an index
  - getFrontIndex
```
public long getFrontIndex(String fanoutId)
```

Class FanOutQueue

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

EARLIEST

LATEST

Constructor Detail

FanOutQueue

FanOutQueue

Method Detail

isEmpty

isEmpty

enqueue

dequeue

peek

peekLength

peekTimestamp

get

getLength

getTimestamp

removeBefore

limitBackFileSize

getBackFileSize

findClosestIndex

resetQueueFrontIndex

size

size

flush

close

removeAll

getFrontIndex

getRearIndex

getFrontIndex