ResourceGuard (Flink : 2.0-SNAPSHOT API)

java.lang.Object
- org.apache.flink.util.ResourceGuard

All Implemented Interfaces:

Serializable, AutoCloseable
```
public class ResourceGuard
extends Object
implements AutoCloseable, Serializable
```
This class is a guard for shared resources with the following invariants. The resource can be acquired by multiple clients in parallel through the acquireResource() call. As a result of the call, each client gets a ResourceGuard.Lease. The close() method of the lease releases the resources and reduces the client count in the ResourceGuard object. The protected resource should only be disposed once the corresponding resource guard is successfully closed, but the guard can only be closed once all clients that acquired a lease for the guarded resource have released it. Before this is happened, the call to close() will block until the zero-open-leases condition is triggered. After the resource guard is closed, calls to acquireResource() will fail with exception. Notice that, obviously clients are responsible to release the resource after usage. All clients are considered equal, i.e. there is only a global count maintained how many times the resource was acquired but not by whom.

See Also:

Serialized Form

Nested Class Summary

Nested Classes
Modifier and Type Class Description

class ResourceGuard.Lease
A lease is issued by the ResourceGuard as result of calls to acquireResource().

Constructor Summary

Constructors
Constructor Description

ResourceGuard()

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`ResourceGuard.Lease`	`acquireResource()`	Acquired access from one new client for the guarded resource.
`void`	`close()`	Closed the resource guard.
`void`	`closeInterruptibly()`
`void`	`closeUninterruptibly()`	If the current thread is interrupted while waiting for the close method to complete, then it will continue to wait.
`int`	`getLeaseCount()`	Returns the current count of open leases.
`boolean`	`isClosed()`	Returns true if the resource guard is closed, i.e. after `close()` was called.

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

- Constructor Detail
  - ResourceGuard
```
public ResourceGuard()
```
- Method Detail
  - acquireResource
```
public ResourceGuard.Lease acquireResource()
                                    throws IOException
```
    Acquired access from one new client for the guarded resource.
    
    Throws:
    
    IOException - when the resource guard is already closed.
  - closeInterruptibly
```
public void closeInterruptibly()
                        throws InterruptedException
```
    Throws:
    
    InterruptedException
  - closeUninterruptibly
```
public void closeUninterruptibly()
```
    If the current thread is interrupted while waiting for the close method to complete, then it will continue to wait. When the thread does return from this method its interrupt status will be set.
  - close
```
public void close()
```
    Closed the resource guard. This method will block until all calls to acquireResource() have seen their matching call to releaseResource().
    
    Specified by:
    
    close in interface AutoCloseable
  - isClosed
```
public boolean isClosed()
```
    Returns true if the resource guard is closed, i.e. after close() was called.
  - getLeaseCount
```
public int getLeaseCount()
```
    Returns the current count of open leases.