Briefly, this error occurs when Elasticsearch fails to clean up the results of an asynchronous task due to an internal issue, such as a problem with the task management system or a network glitch. To resolve this issue, you can try restarting the Elasticsearch node, checking the network connection, or increasing the timeout settings. If the problem persists, you may need to investigate the task management system for any potential bugs or issues.
This guide will help you check for common problems that cause the log ” failed to clean async result [” + taskId.getEncoded() + “] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugin, task.
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 “failed to clean async result [” + taskId.getEncoded() + “]” classname is DeleteAsyncResultsService.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
// the index may not be there (no initial async search response stored yet?): we still want to return 200
// note that index missing comes back as 200 hence it's handled in the onResponse callback
if (status == RestStatus.NOT_FOUND && taskWasFound) {
listener.onResponse(AcknowledgedResponse.TRUE);
} else {
logger.error(() -> "failed to clean async result [" + taskId.getEncoded() + "]"; exc);
listener.onFailure(new ResourceNotFoundException(taskId.getEncoded()));
}
}));
}
}
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