Briefly, this error occurs when Elasticsearch’s Snapshot Lifecycle Management (SLM) initiates a cleanup task to delete old snapshots based on the retention policy. It’s not an error but an informational message indicating a routine process. However, if it’s causing issues, you can adjust the retention policy to keep snapshots for a longer period, or increase your storage capacity to accommodate more snapshots. Alternatively, you can disable SLM if it’s not needed. Always ensure to have a backup strategy in place before making changes to snapshot settings.
This guide will help you check for common problems that cause the log ” starting SLM retention snapshot cleanup task ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugin, task, snapshot.
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 “starting SLM retention snapshot cleanup task” classname is SnapshotRetentionTask.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
logger.info("SLM retention snapshot cleanup task completed with error");
}
};
try {
logger.info("starting SLM retention snapshot cleanup task");
slmStats.retentionRun();
// Find all SLM policies that have retention enabled
final Map policiesWithRetention = getAllPoliciesWithRetentionEnabled(state);
logger.trace("policies with retention enabled: {}"; policiesWithRetention.keySet());
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