org.elasticsearch.persistent.PersistentTasksExecutor Maven / Gradle / Ivy
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/*
* Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
* or more contributor license agreements. Licensed under the Elastic License
* 2.0 and the Server Side Public License, v 1; you may not use this file except
* in compliance with, at your election, the Elastic License 2.0 or the Server
* Side Public License, v 1.
*/
package org.elasticsearch.persistent;
import org.elasticsearch.cluster.ClusterState;
import org.elasticsearch.cluster.node.DiscoveryNode;
import org.elasticsearch.core.Nullable;
import org.elasticsearch.persistent.PersistentTasksCustomMetadata.Assignment;
import org.elasticsearch.persistent.PersistentTasksCustomMetadata.PersistentTask;
import org.elasticsearch.tasks.TaskId;
import java.util.Collection;
import java.util.Map;
import java.util.function.Predicate;
/**
* An executor of tasks that can survive restart of requesting or executing node.
* These tasks are using cluster state rather than only transport service to send requests and responses.
*/
public abstract class PersistentTasksExecutor {
private final String executor;
private final String taskName;
protected PersistentTasksExecutor(String taskName, String executor) {
this.taskName = taskName;
this.executor = executor;
}
public String getTaskName() {
return taskName;
}
public static final Assignment NO_NODE_FOUND = new Assignment(null, "no appropriate nodes found for the assignment");
/**
* Returns the node id where the params has to be executed,
*
* The default implementation returns the least loaded data node from amongst the collection of candidate nodes
*/
public Assignment getAssignment(Params params, Collection candidateNodes, ClusterState clusterState) {
DiscoveryNode discoveryNode = selectLeastLoadedNode(clusterState, candidateNodes, DiscoveryNode::canContainData);
if (discoveryNode == null) {
return NO_NODE_FOUND;
} else {
return new Assignment(discoveryNode.getId(), "");
}
}
/**
* Finds the least loaded node from amongs the candidate node collection
* that satisfies the selector criteria
*/
protected DiscoveryNode selectLeastLoadedNode(
ClusterState clusterState,
Collection candidateNodes,
Predicate selector
) {
long minLoad = Long.MAX_VALUE;
DiscoveryNode minLoadedNode = null;
PersistentTasksCustomMetadata persistentTasks = clusterState.getMetadata().custom(PersistentTasksCustomMetadata.TYPE);
for (DiscoveryNode node : candidateNodes) {
if (selector.test(node)) {
if (persistentTasks == null) {
// We don't have any task running yet, pick the first available node
return node;
}
long numberOfTasks = persistentTasks.getNumberOfTasksOnNode(node.getId(), taskName);
if (minLoad > numberOfTasks) {
minLoad = numberOfTasks;
minLoadedNode = node;
}
}
}
return minLoadedNode;
}
/**
* Checks the current cluster state for compatibility with the params
*
* Throws an exception if the supplied params cannot be executed on the cluster in the current state.
*/
public void validate(Params params, ClusterState clusterState) {}
/**
* Creates a AllocatedPersistentTask for communicating with task manager
*/
protected AllocatedPersistentTask createTask(
long id,
String type,
String action,
TaskId parentTaskId,
PersistentTask taskInProgress,
Map headers
) {
return new AllocatedPersistentTask(id, type, action, getDescription(taskInProgress), parentTaskId, headers);
}
/**
* Returns task description that will be available via task manager
*/
protected String getDescription(PersistentTask taskInProgress) {
return "id=" + taskInProgress.getId();
}
/**
* This operation will be executed on the executor node.
*
* NOTE: The nodeOperation has to throw an exception, trigger task.markAsCompleted() or task.completeAndNotifyIfNeeded() methods to
* indicate that the persistent task has finished.
*/
protected abstract void nodeOperation(AllocatedPersistentTask task, Params params, @Nullable PersistentTaskState state);
public String getExecutor() {
return executor;
}
}