Background Tasks

This page describes the management of background tasks running on Weka clusters.‌

Overview

‌The Weka system has some internal/external asynchronous operations and maintenance tasks, such as migrating an object store and downloading/uploading snapshots. These tasks are performed in the background and should not interfere nor starve the Weka system from serving IOs with high performance.‌

The Weka system limits the CPU resources these tasks consume to 5% per host CPU.

Note: When the CPU is idle, background tasks can use more than the configured resources, but they are immediately freed if needed for serving IOs.

Note: The configured limit affects both external tasks (that are visible using the GUI/CLI) and internal low priority asynchronous operations.‌

Managing Background Tasks

Viewing Running Background Tasks

It is possible to view currently-running background tasks, including their status and progress.‌

Viewing Background Tasks Using the CLI

‌Command: weka cluster tasks‌

This command is used for viewing all background tasks. For each task, a range of data can be displayed, as shown in the following example:

# weka cluster tasks
Type       | State   | Progress | Description
-----------+---------+----------+-----------------------------------------------------------
OBS_DETACH | RUNNING | 94       | Detaching Object Storage `obs_1` from filesystem `default`

‌Limiting Background Task Resources

It is possible to limit the resources being used by background tasks.

Limiting Background Tasks Using the CLI

Command: weka cluster tasks limits

This command is used to view the defined limits.

Command: weka cluster tasks limits set [--cpu-limit cpu-limit]

This command is used to update the CPU limit.

Pausing/Resuming/Aborting a Background Task

It is possible to pause and later resume a background task, as well as completely abort it. This is useful in case there are other tasks/activities that are of higher priority.

Pausing/Resuming/Aborting Background Tasks Using the CLI

Command: weka cluster tasks pause / resume / abort <task-id>

This command is used to pause/resume/abort the running of a specific task.

Note: Up to 16 background tasks can run in parallel. A paused (or aborting) task still consumes one of these spots.