ExpiryQueue (Apache ZooKeeper - Server 3.9.2 API)

java.lang.Object
- org.apache.zookeeper.server.ExpiryQueue<E>

```
public class ExpiryQueue<E>
extends Object
```
ExpiryQueue tracks elements in time sorted fixed duration buckets. It's used by SessionTrackerImpl to expire sessions and NIOServerCnxnFactory to expire connections.

Constructor Summary

Constructors
Constructor Description

ExpiryQueue(int expirationInterval)

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`dump(PrintWriter pwriter)`
`Map<Long,Set<E>>`	`getExpiryMap()`	Returns an unmodifiable view of the expiration time -> elements mapping.
`long`	`getWaitTime()`
`Set<E>`	`poll()`	Remove the next expired set of elements from expireMap.
`Long`	`remove(E elem)`	Removes element from the queue.
`Long`	`update(E elem, int timeout)`	Adds or updates expiration time for element in queue, rounding the timeout to the expiry interval bucketed used by this queue.

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

- Constructor Detail
  - ExpiryQueue
```
public ExpiryQueue(int expirationInterval)
```
- Method Detail
  - remove
```
public Long remove(E elem)
```
    Removes element from the queue.
    
    Parameters:
    
    elem - element to remove
    
    Returns:
    
    time at which the element was set to expire, or null if it wasn't present
  - update
```
public Long update(E elem,
                   int timeout)
```
    Adds or updates expiration time for element in queue, rounding the timeout to the expiry interval bucketed used by this queue.
    
    Parameters:
    
    elem - element to add/update
    
    timeout - timout in milliseconds
    
    Returns:
    
    time at which the element is now set to expire if changed, or null if unchanged
  - getWaitTime
```
public long getWaitTime()
```
    Returns:
    
    milliseconds until next expiration time, or 0 if has already past
  - poll
```
public Set<E> poll()
```
    Remove the next expired set of elements from expireMap. This method needs to be called frequently enough by checking getWaitTime(), otherwise there will be a backlog of empty sets queued up in expiryMap.
    
    Returns:
    
    next set of expired elements, or an empty set if none are ready
  - dump
```
public void dump(PrintWriter pwriter)
```
  - getExpiryMap
```
public Map<Long,Set<E>> getExpiryMap()
```
    Returns an unmodifiable view of the expiration time -> elements mapping.