Before you begin reading this guide, we recommend you run Elasticsearch Error Check-Up which can resolve issues that cause many errors.
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 pinpoint the cause of many errors and provides suitable actionable recommendations how to resolve them (free tool that requires no installation).
Overview
It’s quite essential to understand what Cluster state is and why Elasticsearch makes sure to log a warning if the time taken to update it extends beyond the default threshold of 10 seconds.
The Cluster state consists of the information of all nodes and shards in the cluster and all of the cluster and index level settings.
Cluster state is computed on the master node and published to all nodes in the cluster and is very important for the functioning of the Elasticsearch cluster.
This is why Elasticsearch throws a warning if it’s not able to compute and publish these changes to all the nodes within threshold.
Potential causes and a detailed guide on how to solve and code fragments from Elasticsearch are covered by an Opster ES expert in this STOF answer.
Overview
A task is an Elasticsearch operation, which can be any request performed on an Elasticsearch cluster, such as 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
Where 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 task
Where 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 “Cluster state update task [{}] took [{}] above the warn threshold of {}” classname is MasterService.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
}
}
protected void warnAboutSlowTaskIfNeeded(TimeValue executionTime; String source) {
if (executionTime.getMillis() > slowTaskLoggingThreshold.getMillis()) {
logger.warn("cluster state update task [{}] took [{}] above the warn threshold of {}"; source; executionTime;
slowTaskLoggingThreshold);
}
}
private static class DelegatingAckListener implements Discovery.AckListener {
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