io.atomix.resource

Enum Resource.State

java.lang.Object

java.lang.Enum<Resource.State>

io.atomix.resource.Resource.State

All Implemented Interfaces:

Serializable, Comparable<Resource.State>

Enclosing interface:

Resource<T extends Resource<T>>

public static enum Resource.State
extends Enum<Resource.State>

Resource session state constants.

The resource state is indicative of the resource's ability to communicate with the cluster within the context of the underlying Session. In some cases, resource state changes may be indicative of a loss of guarantees. Users of the resource should watch the state of a resource to determine when guarantees are lost and react to changes in the resource's ability to communicate with the cluster.

   
   resource.onStateChange(state -> {
     switch (state) {
       case OPEN:
         // The resource is healthy
         break;
       case SUSPENDED:
         // The resource is unhealthy and operations may be unsafe
         break;
       case CLOSED:
         // The resource has been closed and pending operations have failed
         break;
     }
   });
   
 

So long as the resource is in the CONNECTED state, all guarantees with respect to reads and writes will be maintained, and a loss of the CONNECTED state may indicate a loss of linearizability. See the specific states for more info.

Reference resource documentation for implications of the various states on specific resources.

Enum Constant Summary

Enum Constants

Enum Constant and Description
CLOSED Indicates that the resource is closed.
CONNECTED Indicates that the resource is connected and operating normally.
SUSPENDED Indicates that the resource is suspended and its session may or may not be expired.

Method Summary

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

Methods inherited from class java.lang.Enum

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

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

CONNECTED

public static final Resource.State CONNECTED

Indicates that the resource is connected and operating normally.

The CONNECTED state indicates that the resource is healthy and operating normally. Operations submitted and completed while the resource is in this state are guaranteed to adhere to the configured consistency level.

SUSPENDED

public static final Resource.State SUSPENDED

Indicates that the resource is suspended and its session may or may not be expired.

The SUSPENDED state is indicative of an inability to communicate with the cluster within the context of the underlying client's Session. Operations performed on resources in this state should be considered unsafe. An operation performed on a CONNECTED resource that transitions to the SUSPENDED state prior to the operation's completion may be committed multiple times in the event that the underlying session is ultimately expired, thus breaking linearizability. Additionally, state machines may see the session expire while the resource is in this state.

A resource that is in the SUSPENDED state may transition back to CONNECTED once its underlying session is recovered. However, operations not yet completed prior to the resource's recovery may lose linearizability guarantees. If an operation is submitted while a resource is in the CONNECTED state and the resource loses and recovers its session, the operation may be applied to the resource's state more than once. Operations completed across sessions are guaranteed to be performed at-least-once only.

CLOSED

public static final Resource.State CLOSED

Indicates that the resource is closed.

A resource may transition to this state as a result of an expired session or an explicit close by the user or a closure of the resource's underlying client.

Method Detail

values

public static Resource.State[] 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 (Resource.State c : Resource.State.values())
    System.out.println(c);

Returns:

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

valueOf

public static Resource.State 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