com.datastax.oss.driver.api.core.metadata

Enum NodeState

java.lang.Object

java.lang.Enum<NodeState>

com.datastax.oss.driver.api.core.metadata.NodeState

All Implemented Interfaces:

Serializable, Comparable<NodeState>

public enum NodeState
extends Enum<NodeState>

The state of a node, as viewed from the driver.

Enum Constant Summary

Enum Constants

Enum Constant and Description
DOWN A node is considered down in either of the following situations: 1) the driver has lost all connections to the node (and is currently trying to reconnect), or 2) the driver is not actively trying to connect to the node (because it's ignored by the LoadBalancingPolicy), but it has received a topology event indicating that the node is down.
FORCED_DOWN The node was forced down externally, the driver will never try to reconnect to it, whatever the LoadBalancingPolicy says.
UNKNOWN The driver has never tried to connect to the node, nor received any topology events about it.
UP A node is considered up in either of the following situations: 1) the driver has at least one active connection to the node, or 2) the driver is not actively trying to connect to the node (because it's ignored by the LoadBalancingPolicy), but it has received a topology event indicating that the node is up.

Method Summary

Modifier and Type	Method and Description
static NodeState	valueOf(String name) Returns the enum constant of this type with the specified name.
static NodeState[]	values() Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

UNKNOWN

public static final NodeState UNKNOWN

The driver has never tried to connect to the node, nor received any topology events about it.

This happens when nodes are first added to the cluster, and will persist if your LoadBalancingPolicy decides to ignore them. Since the driver does not connect to them, the only way it can assess their states is from topology events.

UP

public static final NodeState UP

A node is considered up in either of the following situations: 1) the driver has at least one active connection to the node, or 2) the driver is not actively trying to connect to the node (because it's ignored by the LoadBalancingPolicy), but it has received a topology event indicating that the node is up.

DOWN

public static final NodeState DOWN

A node is considered down in either of the following situations: 1) the driver has lost all connections to the node (and is currently trying to reconnect), or 2) the driver is not actively trying to connect to the node (because it's ignored by the LoadBalancingPolicy), but it has received a topology event indicating that the node is down.

FORCED_DOWN

public static final NodeState FORCED_DOWN

The node was forced down externally, the driver will never try to reconnect to it, whatever the LoadBalancingPolicy says.

This is used for edge error cases, for example when the driver detects that it's trying to connect to a node that does not belong to the Cassandra cluster (e.g. a wrong address was provided in the contact points). It can also be triggered explicitly by components (for example a custom load balancing policy) that want to limit the number of nodes that the driver connects to.

Method Detail

values

public static NodeState[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (NodeState c : NodeState.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static NodeState valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum type has no constant with the specified name

NullPointerException - if the argument is null