WhiteListPolicy (DataStax Java Driver for Apache Cassandra

java.lang.Object
- com.datastax.driver.core.policies.WhiteListPolicy

All Implemented Interfaces:

Host.StateListener, ChainableLoadBalancingPolicy, CloseableLoadBalancingPolicy, LoadBalancingPolicy
```
public class WhiteListPolicy
extends Object
implements ChainableLoadBalancingPolicy, CloseableLoadBalancingPolicy
```
A load balancing policy wrapper that ensure that only hosts from a provided white list will ever be returned.
This policy wraps another load balancing policy and will delegate the choice of hosts to the wrapped policy with the exception that only hosts contained in the white list provided when constructing this policy will ever be returned. Any host not in the while list will be considered IGNORED and thus will not be connected to.
This policy can be useful to ensure that the driver only connects to a predefined set of hosts. Keep in mind however that this policy defeats somewhat the host auto-detection of the driver. As such, this policy is only useful in a few special cases or for testing, but is not optimal in general. If all you want to do is limiting connections to hosts of the local data-center then you should use DCAwareRoundRobinPolicy and *not* this policy in particular.

Constructor Summary

Constructors
Constructor and Description
`WhiteListPolicy(LoadBalancingPolicy childPolicy, Collection<InetSocketAddress> whiteList)` Create a new policy that wraps the provided child policy but only "allow" hosts from the provided while list.

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`close()` Gets invoked at cluster shutdown.
`HostDistance`	`distance(Host host)` Return the HostDistance for the provided host.
`LoadBalancingPolicy`	`getChildPolicy()` Returns the child policy.
`void`	`init(Cluster cluster, Collection<Host> hosts)` Initialize this load balancing policy.
`Iterator<Host>`	`newQueryPlan(String loggedKeyspace, Statement statement)` Returns the hosts to use for a new query.
`void`	`onAdd(Host host)` Called when a new node is added to the cluster.
`void`	`onDown(Host host)` Called when a node is determined to be down.
`void`	`onRemove(Host host)` Called when a node is removed from the cluster.
`void`	`onSuspected(Host host)` Called when a node is suspected to be dead.
`void`	`onUp(Host host)` Called when a node is determined to be up.

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

- Constructor Detail
  - WhiteListPolicy
```
public WhiteListPolicy(LoadBalancingPolicy childPolicy,
               Collection<InetSocketAddress> whiteList)
```
    Create a new policy that wraps the provided child policy but only "allow" hosts from the provided while list.
    
    Parameters:
    childPolicy - the wrapped policy.
    whiteList - the white listed hosts. Only hosts from this list may get connected to (whether they will get connected to or not depends on the child policy).
- Method Detail
  - getChildPolicy
```
public LoadBalancingPolicy getChildPolicy()
```
    Description copied from interface: ChainableLoadBalancingPolicy
    
    Returns the child policy.
    
    Specified by:
    
    getChildPolicy in interface ChainableLoadBalancingPolicy
    
    Returns:
    the child policy.
  - init
```
public void init(Cluster cluster,
        Collection<Host> hosts)
```
    Initialize this load balancing policy.
    
    Specified by:
    
    init in interface LoadBalancingPolicy
    
    Parameters:
    cluster - the Cluster instance for which the policy is created.
    hosts - the initial hosts to use.
    
    Throws:
    
    IllegalArgumentException - if none of the host in hosts (which will correspond to the contact points) are part of the white list.
  - distance
```
public HostDistance distance(Host host)
```
    Return the HostDistance for the provided host.
    
    Specified by:
    
    distance in interface LoadBalancingPolicy
    
    Parameters:
    host - the host of which to return the distance of.
    
    Returns:
    HostDistance.IGNORED if host is not part of the white list, the HostDistance as returned by the wrapped policy otherwise.
  - newQueryPlan
```
public Iterator<Host> newQueryPlan(String loggedKeyspace,
                          Statement statement)
```
    Returns the hosts to use for a new query.
    It is guaranteed that only hosts from the white list will be returned.
    
    Specified by:
    
    newQueryPlan in interface LoadBalancingPolicy
    
    Parameters:
    loggedKeyspace - the currently logged keyspace (the one set through either Cluster.connect(String) or by manually doing a USE query) for the session on which this plan need to be built. This can be null if the corresponding session has no keyspace logged in.
    statement - the query for which to build a plan.
    
    Returns:
    an iterator of Host. The query is tried against the hosts returned by this iterator in order, until the query has been sent successfully to one of the host.
  - onUp
```
public void onUp(Host host)
```
    Description copied from interface: Host.StateListener
    
    Called when a node is determined to be up.
    
    Specified by:
    
    onUp in interface Host.StateListener
    
    Parameters:
    host - the host that has been detected up.
  - onSuspected
```
public void onSuspected(Host host)
```
    Description copied from interface: Host.StateListener
    
    Called when a node is suspected to be dead.
    A node is suspected to be dead when an error occurs on one of it's opened connection. As soon as an host is suspected, a connection attempt to that host is immediately tried. If this succeed, then it means that the connection was disfunctional but that the node was not really down. If this fails however, this means the node is truly dead, onDown() is called and further reconnection attempts are scheduled according to the ReconnectionPolicy in place.
    When this event is triggered, it is possible to call the host getInitialReconnectionAttemptFuture method to wait until the initial and immediate reconnection attempt succeed or fail.
    Note that some StateListener may ignore that event. If a node that that is suspected down turns out to be truly down (that is, the driver cannot successfully connect to it right away), then onDown will be called.
    
    Specified by:
    
    onSuspected in interface Host.StateListener
  - onDown
```
public void onDown(Host host)
```
    Description copied from interface: Host.StateListener
    
    Called when a node is determined to be down.
    
    Specified by:
    
    onDown in interface Host.StateListener
    
    Parameters:
    host - the host that has been detected down.
  - onAdd
```
public void onAdd(Host host)
```
    Description copied from interface: Host.StateListener
    
    Called when a new node is added to the cluster.
    The newly added node should be considered up.
    
    Specified by:
    
    onAdd in interface Host.StateListener
    
    Parameters:
    host - the host that has been newly added.
  - onRemove
```
public void onRemove(Host host)
```
    Description copied from interface: Host.StateListener
    
    Called when a node is removed from the cluster.
    
    Specified by:
    
    onRemove in interface Host.StateListener
    
    Parameters:
    host - the removed host.
  - close
```
public void close()
```
    Description copied from interface: CloseableLoadBalancingPolicy
    
    Gets invoked at cluster shutdown. This gives the policy the opportunity to perform some cleanup, for instance stop threads that it might have started.
    
    Specified by:
    
    close in interface CloseableLoadBalancingPolicy

Class WhiteListPolicy

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

WhiteListPolicy

Method Detail

getChildPolicy

init

distance

newQueryPlan

onUp

onSuspected

onDown

onAdd

onRemove

close