Briefly, this error occurs when Elasticsearch Machine Learning (ML) completes a maintenance task to delete expired data. It’s not an error but an informational message indicating that the task has been successfully executed. If you don’t want to see these messages, you can adjust the logging level in Elasticsearch settings. Alternatively, if you don’t use ML features, you can disable them to prevent such tasks from running.
This guide will help you check for common problems that cause the log ” Successfully completed [ML] maintenance task: triggerDeleteExpiredDataTask ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugin, task, delete.
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.
Overview
DELETE is an Elasticsearch API which removes a document from a specific index. This API requires an index name and _id document to delete the document.
Delete a document
DELETE /my_index/_doc/1
Notes
- A delete request throws 404 error code if the document does not already exist in the index.
- If you want to delete a set of documents that matches a query, you need to use delete by query API.
Log Context
Log “Successfully completed [ML] maintenance task: triggerDeleteExpiredDataTask” classname is MlDailyMaintenanceService.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
private void triggerDeleteExpiredDataTask(ActionListener finalListener) {
ActionListener deleteExpiredDataActionListener = ActionListener.wrap(
deleteExpiredDataResponse -> {
if (deleteExpiredDataResponse.isDeleted()) {
logger.info("Successfully completed [ML] maintenance task: triggerDeleteExpiredDataTask");
} else {
logger.info("Halting [ML] maintenance tasks before completion as elapsed time is too great");
}
finalListener.onResponse(AcknowledgedResponse.TRUE);
};
