Background tasks

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

‌The Weka system performs internal and external asynchronous operations and maintenance tasks in the background, allowing no interference nor starving the Weka system from serving IOs with high performance.‌

Background tasks include, for example, downloading and uploading snapshots and migrating an object store.

Adhere to the following:

• CPU resource consumption: The Weka system limits these tasks’ CPU resources to 5% of the overall CPU. When the CPU is idle, background tasks can use more than the configured resources but are immediately freed if needed for serving IOs.

• Concurrent tasks: The maximum number of concurrent tasks is 16, with restrictions such as:

  • Only a single local upload can exist inside a filesystem concurrently.

  • Only a single remote upload inside a filesystem concurrently (but local and remote uploads can co-exist).

  • Only a single upload from any filesystem can exist in the same object store bucket to prevent slowing down each other uploads.

  • Object store snapshot download operation cannot be run simultaneously with other snapshot download or upload operations.

Note: More restrictions exist between different tasks and multiple tasks of the same type. If a background task does not run due to a restriction, the system provides a relevant message.

Manage background tasks

View 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 task‌

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 task
Type       | State   | Progress | Description
-----------+---------+----------+-----------------------------------------------------------
OBS_DETACH | RUNNING | 94       | Detaching Object Storage `obs_1` from filesystem `default`

‌Limit background task resources

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

Limit background tasks using the CLI

Command: weka cluster task limits

This command is used to view the defined limits.

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

This command is used to update the CPU limit.

Pause/Resume/Abort 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.

Pause/Resume/Abort a background task using the CLI

Command: weka cluster task 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.