Updated: July-20
Elasticsearch Version: 1.7-8.0
Before you begin reading this guide, we recommend you try running the Elasticsearch Error Check-Up which can resolve issues causing many errors
This guide will help you check for common problems that cause the log “task isn’t running and hasn’t stored its results” to appear. It’s important to understand the issues related to the log, so to get started, read the general overview on common issues and tips related to the Elasticsearch concepts: admin, node, task, cluster.
Advanced users might want to skip right to the common problems section in each concept or try running the Check-Up which analyses ES to discover the cause of many errors and provides suitable actionable recommendations (free tool that requires no installation).
Nodes in Elasticsearch
What it is
Simply explained a node is a single server that is part of a cluster. Each node is assigned with one or more roles, which describes the node responsibility and operations – Data nodes stores the data, and participates in the cluster’s indexing and search capabilities, while master nodes are responsible for managing the cluster activities and storing the cluster state, including the metadata.
While it’s possible to run several Node instances of Elasticsearch on the same hardware, it’s considered a best practice to limit a server to a single running instance of Elasticsearch.
Nodes connect to each other and form a cluster by using a discovery method.
Roles
Master node
Master nodes are in charge of cluster-wide settings and changes – deleting or creating indices and fields, adding or removing nodes and allocating shards to nodes. Each cluster has a single master node that is elected from the master eligible nodes using a distributed consensus algorithm and is reelected if the current master node fails.
Coordinator Node (aka client node)
Coordinator Node – is a node that does not hold any configured role. It doesn’t hold data, not part of the master eligible group nor execute ingest pipelines. Coordinator node serves incoming search requests and is acting as the query coordinator – running the query and fetch phases, sending requests to every node which holds a shard being queried. The client node also distributes bulk indexing operations and route queries to shards copies based on the nodes responsiveness.
Task in Elasticsearch
What it is
A task is equivalent to an Elasticsearch operation, which can be any request performed on an Elasticsearch cluster. For example, a delete by query request, a search request and so on. Elasticsearch provides a dedicated Task API for the task management which includes various actions, from retrieving the status of current running tasks to canceling any long running task.
Examples
Get all currently running tasks on all nodes of the cluster
Apart from other information, the response of the below request contains task IDs of all the tasks which can be used to get detailed information about the particular task in question.
GET _tasks
GET detailed information of a particular task
clQFAL_VRrmnlRyPsu_p8A:1132678759 is the ID of the task in below request.
GET _tasks/clQFAL_VRrmnlRyPsu_p8A:1132678759
Get all the current tasks running on particular nodes
GET _tasks?nodes=nodeId1,nodeId2
Cancel a long-running task
clQFAL_VRrmnlRyPsu_p8A:1132678759 is the ID of the task in the below request.
POST /_tasks/clQFAL_VRrmnlRyPsu_p8A:1132678759/_cancel?pretty
Notes
- The Task API will be most useful when you want to investigate the spike of resource utilization in the cluster or want to cancel an operation.
Log Context
Log”task [{}] isn’t running and hasn’t stored its results”classname is TransportGetTaskAction.java
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
get.setParentTask(clusterService.localNode().getId(); thisTask.getId());
client.get(get; ActionListener.wrap(r -> onGetFinishedTaskFromIndex(r; listener); e -> {
if (ExceptionsHelper.unwrap(e; IndexNotFoundException.class) != null) {
// We haven't yet created the index for the task results so it can't be found.
listener.onFailure(new ResourceNotFoundException("task [{}] isn't running and hasn't stored its results"; e;
request.getTaskId()));
} else {
listener.onFailure(e);
}
}));Related issues to this log
We have gathered selected Q&A from the community and issues from Github, that can help fix related issues please review the following for further information :
1 Update_By_Query not creating task -views 86
2 Elasticsearch reindex tasks 404ing -views 35
