com.datastax.driver.core

Interface Host.StateListener

All Known Subinterfaces:

ChainableLoadBalancingPolicy, LoadBalancingPolicy

All Known Implementing Classes:

DCAwareRoundRobinPolicy, LatencyAwarePolicy, RoundRobinPolicy, TokenAwarePolicy, WhiteListPolicy

Enclosing class:

Host

public static interface Host.StateListener

Interface for listeners that are interested in hosts added, up, down and removed events.

It is possible for the same event to be fired multiple times, particularly for up or down events. Therefore, a listener should ignore the same event if it has already been notified of a node's state.

Method Summary

Methods

Modifier and Type	Method and Description
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.

Method Detail

onAdd

void onAdd(Host host)

Called when a new node is added to the cluster.

The newly added node should be considered up.

Parameters:

host - the host that has been newly added.

onUp

void onUp(Host host)

Called when a node is determined to be up.

Parameters:

host - the host that has been detected up.

onSuspected

void onSuspected(Host host)

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 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(com.datastax.driver.core.Host) will be called.

onDown

void onDown(Host host)

Called when a node is determined to be down.

Parameters:

host - the host that has been detected down.

onRemove

void onRemove(Host host)

Called when a node is removed from the cluster.

Parameters:

host - the removed host.