Task Retention and Result

Task Retention

By default, a task is deleted from the queue once it's successfully processed by Handler (i.e. Handler.ProcessTask returns nil). However, if you'd like to keep the task in the queue after its completion (e.g. for inspection purpose), you can specify a retention period for the task.

Here is an example of using Retention option to specify task to be kept in the queue for 24h after its completion.

// Set the option at task initialization.
task := asynq.NewTask("my_task", payload, asynq.Retention(24 * time.Hour))

// Or alternatively, set the option at enqueue time.
info, err := client.Enqueue(task, asynq.Retention(24 * time.Hour))

With this option set, you should be able to see the completed task using the CLI or Web UI.

Task Result

If you'd like to store some data associated with a task when it's processed, and if the data is only needed during the lifetime of the task (i.e. until it's deleted from the queue), then you can simply store the data with the task.

Use ResultWriter to write the data to redis so that the written data is associated with the task.

Note: Be cautious of the amount of data you write to redis, if the data you need to store is large, it maybe better to use a disk-based storage system like a SQL database.

// In handler code.
func MyHandler(ctx context.Context, task *asynq.Task) error {
    res, err := DoStuff(ctx, task)
    if err != nil {
        return fmt.Errorf("failed to process task: %v", err)
    }
    if _, err = task.ResultWriter().Write(res); err != nil {
        return fmt.Errorf("failed to write task result: %v", err)
    }
    return nil
}

If you use this in conjunction with the Retention option shown above, you'll be able to see the result data via CLI and Web UI. Also, the result data is accessible programmatically by using Inspector.GetTaskInfo and Inspector.ListCompletedTasks.