org.janusgraph.diskstorage.idmanagement

Enum ConflictAvoidanceMode

java.lang.Object

java.lang.Enum<ConflictAvoidanceMode>

org.janusgraph.diskstorage.idmanagement.ConflictAvoidanceMode

All Implemented Interfaces:

Serializable, Comparable<ConflictAvoidanceMode>

public enum ConflictAvoidanceMode
extends Enum<ConflictAvoidanceMode>

Represents ID allocation strategies for avoiding contention between concurrent JanusGraph instances using a shared storage backend. These strategies are implemented in ConsistentKeyIDAuthority.

Enum Constant Summary

Enum Constants

Enum Constant and Description
GLOBAL_AUTO JanusGraph randomly selects a tag from the space of all possible tags when performing allocations.
GLOBAL_MANUAL The user assigns a tag to each JanusGraph instance.
LOCAL_MANUAL Expert feature: use with care. The user manually assigns each JanusGraph instance a unique conflict avoidance tag in its local graph configuration.
NONE Disables ID allocation conflict avoidance.

Method Summary

Modifier and Type	Method and Description
static ConflictAvoidanceMode	valueOf(String name) Returns the enum constant of this type with the specified name.
static ConflictAvoidanceMode[]	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

NONE

public static final ConflictAvoidanceMode NONE

Disables ID allocation conflict avoidance. This setting does not compromise correctness. However, in a clustered JanusGraph deployment, this may result in ID allocations frequently failing due to contention and then retrying, slowing overall write throughput.

LOCAL_MANUAL

public static final ConflictAvoidanceMode LOCAL_MANUAL

Expert feature: use with care. The user manually assigns each JanusGraph instance a unique conflict avoidance tag in its local graph configuration. The tag becomes part of globally-visible graph element IDs allocated by that JanusGraph instance. Each JanusGraph instance assumes it has exclusive control over its tag, and it uses datacenter-local-quorum-level consistency (on storage backends that support this concept) when allocating IDs with its tag.

This is useful for reducing write latency in JanusGraph deployments atop a multi-datacenter distributed store.

When this mode is set, the user is responsible for setting a unique tag in each JanusGraph graph configuration. Setting the same tag on two different JanusGraph configurations can lead to silent graph corruption in this mode! Each tag must be unique. If you're unsure about this or its implications, then use one of the other modes instead.

GLOBAL_MANUAL

public static final ConflictAvoidanceMode GLOBAL_MANUAL

The user assigns a tag to each JanusGraph instance. The tags should be globally unique for optimal performance, but duplicates will not compromise correctness. The tag becomes part of globally-visible graph element IDs allocated by the instance. If each instance has a unique tag, then ID allocations will never conflict.

Unlike LOCAL_MANUAL, setting the same tag on multiple instances is safe in this mode. JanusGraph uses global-quorum-level or greater on storage backends that have a notion of eventual consistency, so JanusGraph will detect contention and avoid double allocation even when multiple instances share a tag.

GLOBAL_AUTO

public static final ConflictAvoidanceMode GLOBAL_AUTO

JanusGraph randomly selects a tag from the space of all possible tags when performing allocations. Like GLOBAL_MANUAL, this uses at least global-quorum-level consistency, so even if two instances happen to select the same ID simultaneously, the conflict will still be detected.

Method Detail

values

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

Returns:

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

valueOf

public static ConflictAvoidanceMode 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