WorkbenchEntry (BUbiNG 0.9.15)

java.lang.Object
- it.unimi.di.law.bubing.frontier.WorkbenchEntry

All Implemented Interfaces:

java.lang.Comparable<java.util.concurrent.Delayed>, java.util.concurrent.Delayed
```
public final class WorkbenchEntry
extends java.lang.Object
implements java.util.concurrent.Delayed
```
An element of the Workbench.
A workbench entry is associated with a single IP address (actually, to a 64-bit hash of an IP address, to accommodate for IPv6), and contains a queue of all visit states associated with that address, prioritized by VisitState.nextFetch. The queue can be modified using the synchronized methods add(VisitState), remove(), size() and isEmpty().
A nonempty workbench entry is a Delayed object whose priority is given by the maximum between its nextFetch and the VisitState.nextFetch of the top of the queue. The delay, if any, is given by the priority minus System.currentTimeMillis(). This setup makes it possible to just take a WorkbenchEntry from the Workbench and remove its top VisitState, with the guarantee that it is ready to be visited. Moreover, if there at least one VisitState that is ready to be visited, the method will not block.
A workbench entry is either acquired or not. If it not acquired, it is on the workbench if and only if it is nonempty.

Field Summary

Fields
Modifier and Type	Field	Description
`protected boolean`	`acquired`	Whether this entry has been acquired.
`byte[]`	`ipAddress`	The IP address of this workbench entry, computed by `DnsResolver.resolve(String)`.
`protected long`	`nextFetch`	The minimum time at which visit states in this entry can be accessed because of IP-based politeness.

Constructor Summary

Constructors
Constructor	Description
`WorkbenchEntry(byte[] ipAddress, java.util.concurrent.atomic.AtomicLong brokenVisitStates)`	Creates a workbench entry for a given IP address.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`add(VisitState visitState)`	Adds the given visit state to the visit-state queue.
`void`	`add(VisitState visitState, Workbench workbench)`	Adds the given visit state to the visit-state queue, and adds this entry to the workbench if it was empty and not acquired.
`int`	`compareTo(java.util.concurrent.Delayed o)`
`long`	`getDelay(java.util.concurrent.TimeUnit unit)`
`boolean`	`isEmpty()`	Returns true if the visit-state queue is not empty.
`boolean`	`isEntirelyBroken()`	Returns true if this entry is nonempty and all its visit states are broken (i.e., `VisitState.lastExceptionClass` ≠ `null`)
`long`	`nextFetch()`	Returns the minimum time at which some URL in some `VisitState` of the visit-state queue of this workbench entry can be accessed.
`void`	`putOnWorkbenchIfNotEmpty(Workbench workbench)`	Puts this entry on the workbench, if not empty.
`VisitState`	`remove()`	Removes the top element from the visit-state queue.
`int`	`size()`	Returns the number of visit states currently in the visit-state queue.
`java.lang.String`	`toString()`
`VisitState[]`	`visitStates()`	Returns the visit states currently in the queue.

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

- Field Detail
  - ipAddress
```
public final byte[] ipAddress
```
    The IP address of this workbench entry, computed by DnsResolver.resolve(String).
  - acquired
```
protected boolean acquired
```
    Whether this entry has been acquired.
  - nextFetch
```
protected volatile long nextFetch
```
    The minimum time at which visit states in this entry can be accessed because of IP-based politeness.
- Constructor Detail
  - WorkbenchEntry
```
public WorkbenchEntry(byte[] ipAddress,
                      java.util.concurrent.atomic.AtomicLong brokenVisitStates)
```
    Creates a workbench entry for a given IP address.
    
    Parameters:
    
    ipAddress - the IP address.
    
    brokenVisitStates - a reference to Frontier.brokenVisitStates.
- Method Detail
  - isEntirelyBroken
```
public boolean isEntirelyBroken()
```
    Returns true if this entry is nonempty and all its visit states are broken (i.e., VisitState.lastExceptionClass ≠ null)
    
    Returns:
    
    true if this entry is nonempty and all its visit states are broken.
  - add
```
public void add(VisitState visitState)
```
    Adds the given visit state to the visit-state queue.
    This method is used for deserialization only.
    
    Parameters:
    
    visitState - the visit state that must be added to the visit-state queue.
    
    See Also:
    
    PriorityQueue.add(Object)
  - remove
```
public VisitState remove()
```
    Removes the top element from the visit-state queue.
    
    Returns:
    
    the top element from the visit-state queue.
    
    See Also:
    
    AbstractQueue.remove()
  - putOnWorkbenchIfNotEmpty
```
public void putOnWorkbenchIfNotEmpty(Workbench workbench)
```
    Puts this entry on the workbench, if not empty.
    - Preconditions: acquired.
    - Postconditions: not acquired.
    Parameters:
    
    workbench - the workbench.
  - add
```
public void add(VisitState visitState,
                Workbench workbench)
```
    Adds the given visit state to the visit-state queue, and adds this entry to the workbench if it was empty and not acquired.
    
    Parameters:
    
    visitState - the nonempty visit state that must be added to the visit-state queue.
    
    workbench - the workbench.
    
    See Also:
    
    PriorityQueue.add(Object)
  - size
```
public int size()
```
    Returns the number of visit states currently in the visit-state queue.
    
    Returns:
    
    the number of visit states currently in the visit-state queue.
  - visitStates
```
public VisitState[] visitStates()
```
    Returns the visit states currently in the queue.
    This method is mainly useful to compute statistics The returned array is created with the current queue content, and it will not reflect changes of the queue. In particular, some visit states might have an empty URL queue because of concurrent modifications.
    
    Returns:
    
    the visit states currently in the queue.
    
    See Also:
    
    PriorityQueue.toArray()
  - isEmpty
```
public boolean isEmpty()
```
    Returns true if the visit-state queue is not empty.
    
    Returns:
    
    true if the visit-state queue is not empty.
  - nextFetch
```
public long nextFetch()
```
    Returns the minimum time at which some URL in some VisitState of the visit-state queue of this workbench entry can be accessed. It is computed by maximizing nextFetch with VisitState.nextFetch of the top element of the visit-state queue.
    Note that this method will access blindly the top element, which might cause a NullPointerException if the visit-state queue is empty. Thus, great care must be exercised in placing on the workbench entries with a nonempty visit-state queue only.
    
    Returns:
    
    the minimum time at which some URL in some VisitState of this entry can be accessed.
  - getDelay
```
public long getDelay(java.util.concurrent.TimeUnit unit)
```
    Specified by:
    
    getDelay in interface java.util.concurrent.Delayed
  - compareTo
```
public int compareTo(java.util.concurrent.Delayed o)
```
    Specified by:
    
    compareTo in interface java.lang.Comparable<java.util.concurrent.Delayed>
  - toString
```
public java.lang.String toString()
```
    Overrides:
    
    toString in class java.lang.Object

Class WorkbenchEntry

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

ipAddress

acquired

nextFetch

Constructor Detail

WorkbenchEntry

Method Detail

isEntirelyBroken

add

remove

putOnWorkbenchIfNotEmpty

add

size

visitStates

isEmpty

nextFetch

getDelay

compareTo

toString