Module org.elasticsearch.server

Package org.elasticsearch.cluster.metadata

Class DesiredNodes

java.lang.Object

org.elasticsearch.cluster.metadata.DesiredNodes

All Implemented Interfaces:

Iterable<DesiredNodeWithStatus>, Writeable, ToXContent, ToXContentObject

public class DesiredNodes
extends Object
implements Writeable, ToXContentObject, Iterable<DesiredNodeWithStatus>

Desired nodes represents the cluster topology that the operator of the cluster is aiming for. Therefore, it is possible that the desired nodes contain nodes that are not part of the cluster in contrast to DiscoveryNodes that contains only nodes that are part of the cluster.

This concept is useful as it provides more context about future topology changes to the system as well as the desired set of nodes in the cluster, allowing it to make better decisions about allocation, autoscaling, auto-expand replicas, etc.

Additionally, settings validation is done during desired nodes updates avoiding boot-looping when an invalid setting is provided before the node is started.

To modify the desired nodes it is necessary to provide the entire collection of nodes that will be part of the proposed cluster topology.

Desired nodes are expected to be part of a lineage defined by the provided historyId. The historyId is provided by the orchestrator taking care of managing the cluster. In order to identify the different proposed desired nodes within the same history, it is also expected that the orchestrator provides a monotonically increasing version when it communicates about future topology changes. The cluster rejects desired nodes updated with a version less than or equal than the current version for the same historyId.

The historyId is expected to remain stable during the cluster lifecycle, but it is possible that the orchestrator loses its own state and needs to be restored to a previous point in time with an older desired nodes version. In those cases it is expected to use new historyId that would allow starting from a different version.

Each DesiredNode part of DesiredNodes has a DesiredNodeWithStatus.Status depending on whether or not the node has been part of the cluster at some point.

The two possible statuses DesiredNodeWithStatus.Status are:

• PENDING: The DesiredNode is not part of the cluster yet
• ACTUALIZED: The DesiredNode is or has been part of the cluster. Notice that it is possible that a node has ACTUALIZED status but it is not part of DiscoveryNodes, this is a conscious decision as it is expected that nodes can leave the cluster momentarily due to network issues, gc pressure, restarts, hardware failures etc, but are expected to still be part of the cluster.

See NodeJoinExecutor and TransportUpdateDesiredNodesAction for more details about desired nodes status tracking.

Finally, each DesiredNode is expected to provide a way of identifying the node when it joins, Node.NODE_EXTERNAL_ID_SETTING allows providing that identity through settings.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static enum	DesiredNodes.SerializationContext

Nested classes/interfaces inherited from interface org.elasticsearch.xcontent.ToXContent

ToXContent.DelegatingMapParams, ToXContent.MapParams, ToXContent.Params

Nested classes/interfaces inherited from interface org.elasticsearch.common.io.stream.Writeable

Writeable.Reader<V>, Writeable.Writer<V>

Field Summary

Fields

Modifier and Type	Field	Description
static final String	CONTEXT_MODE_API
static final String	CONTEXT_MODE_CLUSTER_STATE
static final String	CONTEXT_MODE_PARAM
static final ConstructingObjectParser<DesiredNodes,Void>	PARSER

Fields inherited from interface org.elasticsearch.xcontent.ToXContent

EMPTY, EMPTY_PARAMS

Method Summary

Modifier and Type	Method	Description
Set<DesiredNode>	actualized()
static DesiredNodes	create(String historyID, long version, List<DesiredNodeWithStatus> nodes)
static DesiredNodes	createIncludingStatusFromPreviousVersion(String historyId, long version, List<DesiredNode> nodes, DesiredNodes previousDesiredNodes)
boolean	equals(Object o)
boolean	equalsNodesWithProcessorsCloseTo(DesiredNodes that)
boolean	equalsWithProcessorsCloseTo(DesiredNodes that)
DesiredNodeWithStatus	find(String externalId)
int	hashCode()
boolean	hasSameHistoryId(DesiredNodes other)
boolean	hasSameVersion(DesiredNodes other)
String	historyID()
boolean	isSupersededBy(DesiredNodes otherDesiredNodes)
Iterator<DesiredNodeWithStatus>	iterator()
static DesiredNodes	latestFromClusterState(ClusterState clusterState)
Set<DesiredNodeWithStatus>	nodes()
Set<DesiredNode>	pending()
static DesiredNodes	readFrom(StreamInput in)
String	toString()
XContentBuilder	toXContent(XContentBuilder builder, ToXContent.Params params)
static ClusterState	updateDesiredNodesStatusIfNeeded(ClusterState clusterState)
static DesiredNodes	updateDesiredNodesStatusIfNeeded(DiscoveryNodes discoveryNodes, DesiredNodes desiredNodes)
long	version()
void	writeTo(StreamOutput out)	Write this into the StreamOutput.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Methods inherited from interface org.elasticsearch.xcontent.ToXContentObject

isFragment

Field Details

CONTEXT_MODE_PARAM

public static final String CONTEXT_MODE_PARAM

See Also:

• Constant Field Values

CONTEXT_MODE_API

public static final String CONTEXT_MODE_API

CONTEXT_MODE_CLUSTER_STATE

public static final String CONTEXT_MODE_CLUSTER_STATE

PARSER

public static final ConstructingObjectParser<DesiredNodes,Void> PARSER

Method Details

readFrom

public static DesiredNodes readFrom(StreamInput in)
                             throws IOException

Throws:

IOException

writeTo

public void writeTo(StreamOutput out)
             throws IOException

Description copied from interface: Writeable

Write this into the StreamOutput.

Specified by:

writeTo in interface Writeable

Throws:

IOException

toXContent

public XContentBuilder toXContent(XContentBuilder builder,
 ToXContent.Params params)
                           throws IOException

Specified by:

toXContent in interface ToXContent

Throws:

IOException

createIncludingStatusFromPreviousVersion

public static DesiredNodes createIncludingStatusFromPreviousVersion(String historyId,
 long version,
 List<DesiredNode> nodes,
 @Nullable
 DesiredNodes previousDesiredNodes)

create

public static DesiredNodes create(String historyID,
 long version,
 List<DesiredNodeWithStatus> nodes)

latestFromClusterState

@Nullable
public static DesiredNodes latestFromClusterState(ClusterState clusterState)

isSupersededBy

public boolean isSupersededBy(DesiredNodes otherDesiredNodes)

hasSameVersion

public boolean hasSameVersion(DesiredNodes other)

hasSameHistoryId

public boolean hasSameHistoryId(DesiredNodes other)

equalsWithProcessorsCloseTo

public boolean equalsWithProcessorsCloseTo(DesiredNodes that)

equalsNodesWithProcessorsCloseTo

public boolean equalsNodesWithProcessorsCloseTo(DesiredNodes that)

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object

historyID

public String historyID()

version

public long version()

nodes

public Set<DesiredNodeWithStatus> nodes()

actualized

public Set<DesiredNode> actualized()

pending

public Set<DesiredNode> pending()

iterator

public Iterator<DesiredNodeWithStatus> iterator()

Specified by:

iterator in interface Iterable<DesiredNodeWithStatus>

find

@Nullable
public DesiredNodeWithStatus find(String externalId)

updateDesiredNodesStatusIfNeeded

public static ClusterState updateDesiredNodesStatusIfNeeded(ClusterState clusterState)

updateDesiredNodesStatusIfNeeded

public static DesiredNodes updateDesiredNodesStatusIfNeeded(DiscoveryNodes discoveryNodes,
 DesiredNodes desiredNodes)