TaskQueue (Wavefront Proxy 8.1 API)

Type Parameters:

T - type of objects stored.

All Known Implementing Classes:

DataSubmissionQueue, TaskQueueStub
```
public interface TaskQueue<T extends DataSubmissionTask<T>>
```
Proxy-specific queue interface, which is basically a wrapper for a Tape queue. This allows us to potentially support more than one backing storage in the future.

Author:

[email protected].

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`void`	`add(T t)`	Add a task to the end of the queue
`void`	`clear()`	Empty and re-initialize the queue.
`void`	`close()`	Close the queue.
`Long`	`getAvailableBytes()`	Returns the total number of pre-allocated but unused bytes in the backing file.
`T`	`peek()`	Retrieve a task that is currently at the head of the queue.
`void`	`remove()`	Remove a task from the head of the queue.
`int`	`size()`	Returns a number of tasks currently in the queue.
`Long`	`weight()`	Returns the total weight of the queue (sum of weights of all tasks).

- Method Detail
  - peek
```
T peek()
```
    Retrieve a task that is currently at the head of the queue.
    
    Returns:
    
    task object
  - add
```
void add(@Nonnull
         T t)
  throws IOException
```
    Add a task to the end of the queue
    
    Parameters:
    
    t - task
    
    Throws:
    
    IOException - IO exceptions caught by the storage engine
  - remove
```
void remove()
     throws IOException
```
    Remove a task from the head of the queue. Requires peek() to be called first, otherwise an IllegalStateException is thrown.
    
    Throws:
    
    IOException - IO exceptions caught by the storage engine
  - clear
```
void clear()
```
    Empty and re-initialize the queue.
  - size
```
int size()
```
    Returns a number of tasks currently in the queue.
    
    Returns:
    
    number of tasks
  - close
```
void close()
```
    Close the queue. Should be invoked before a graceful shutdown.
  - weight
```
@Nullable
Long weight()
```
    Returns the total weight of the queue (sum of weights of all tasks).
    
    Returns:
    
    weight of the queue (null if unknown)
  - getAvailableBytes
```
@Nullable
Long getAvailableBytes()
```
    Returns the total number of pre-allocated but unused bytes in the backing file. May return null if not applicable.
    
    Returns:
    
    total number of available bytes in the file or null